The LED-type Voigtländer VCII that I’ve used for over ten years takes long enough to drain its twin A76/LR44 batteries, which I think I’ve only replaced twice. Since these are very common batteries used in many popular cameras like the Pentax K1000, Nikon FM series, and Leica M’s, you only have to keep one type of spare in your camera bags.

In the last case, the object is situated at the front focal plane of the convex lens. In this case, the rays of light emerge from the lens in parallel. The image is located on the same side of the lens as the object, and it appears upright (see Figure 1). The image is a virtual image and appears as if it were 10 inches from the eye, similar to the functioning of a simple magnifying glass; the magnification factor depends on the curvature of the lens.

Original vintage accessory shoe meters of the 1950s were made of brass and finished in thick satin chrome, but seldom are we treated to this level of luxury today. The Reveni Labs Light Meter Mk.2 is like the Model T of light meters – you can have it your favorite color so long as your favorite color is black 3D printed plastic. Brass is of course a higher regarded metal than aluminum due to being more hard-wearing and it is a better match for many of our classic cameras too. With use, the black paint will wear down to expose the bright brass underneath like a photojournalist’s camera.

Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.

The position of the mounting foot on the TTArtisans Meter & Meter II is adjustable but the foot itself is simple, without any tensioning mechanism like the original Voigtländer VCII. However, the DOOMO Meter D foot features spring clips that allow it to work very well with earlier cameras that have simple accessory shoes.

Sep 6, 2024 — when youre under natural light you can see perfectly but any kind of shadow its pitch black. its like the shadows are 90 times darker and ...

After years of using DOOMO, TTArtisans, Sekonic, and Voigtlander meters; and doing recent product tests for AstrHori, DOOMO, Hedeco, and KEKS I’ve come up with this guide to accessory shoe light meters.

The object is now moved closer to the front of the lens but is still more than two focal lengths in front of the lens (this scenario is addressed in Figure 3). Now, the image is found further behind the lens. It is larger than the one described above, but is still smaller than the object. The image is inverted, and is a real image. This is the case for ordinary portrait photography.

Whichmagnificationrequires most illumination

From a purely theoretical technical perspective, LCD and LED displays should provide the most conservative battery consumption. However, blogger Jim Grey’s LCD-type Reflx Lab Light Meter seemed to kill its single CR1632 battery within hours of use! Similarly surprising, my LED-type TTArtisans Meter required a replacement battery after less than one year of conservative use.

The other concern with the side-mounted shoes of TLRs is that of course the top of the meter is now oriented at a right angle from the viewfinder. So I got into the habit of rotating my camera on its side to take a reading and rotating it back for all other operations.

But top-mounted LED and OLED displays are not always readable in bright sun. The Voigtländer VCII is the most visible two-dial meter, requiring very little shading with one’s hand. And no OLED meters are fully visible in bright sun. This makes models with rear-mounted displays such as the KEKS KM01C, KEKS KM02, KEKS KM-Q, and Reveni Labs Light Meter Mk.2 smart purchases for those who are not doing as much candid and walk-around photography but are often shooting in bright sun. Their rear-mounted displays guarantee better shading or are easier to shade with one’s hand without interfering with the light sensor.

Does the depth of fieldincrease or decreasewithmagnification

The Reflx Lab Light Meter is only a little larger than the Reveni and features just two buttons instead of the four of the Reveni and KEKS KM-Q. This allows those buttons and LCD screen to be a bit larger and potentially easier to navigate/view.

These basic principles underlie the operation and construction of the compound microscope which, unlike a magnifying glass or simple microscope, employs a group of lenses aligned in series. The elaboration of these principles has led to the development, over the past several hundred years, of today's sophisticated instruments. Modern microscopes are often modular with interchangeable parts for different purposes; such microscopes are capable of producing images from low to high magnification with remarkable clarity and contrast.

Does working distanceincreasewith highermagnification

Vintage accessory shoe light meters featured swing needle displays but there are three kinds of read-out now. They are; LCD, LED, and OLED. Which display you choose depends on a few circumstances that I’ll get further into below. Suffice it to say, the main physical differences are in display size, battery consumption, and menu options.

Current iterations of the AstrHori AH-M1, AstrHori XH-2, DOOMO Meter D, DOOMO Meter S, and Reveni Labs Light Meter Mk.2 feature spring-loaded feet that facilitate effortless installation on numerous accessory shoe types. The Hedeco Lime II features a ball-bearing tensioner that can easily be lost when changing foot position but works well otherwise. I have had no difficulty securing these meters on my earliest 1930s Leica and Contax rangefinders to my newest 1990’s Leica M6 rangefinders and 2000’s Nikon SLRs.

In addition to the parallelizing lenses used in some microscopes, manufacturers may also provide additional lenses (sometimes called magnification changers) that can be rotated into the optical pathway to increase the magnification factor. This is often done to provide ease in specimen framing for photomicrography. These lenses usually have very small magnification factors ranging from 1.25X up to 2.5X, but use of these lenses may lead to empty magnification, a situation where the image is enlarged, but no additional detail is resolved. This type of error is illustrated in Figure 7 with photomicrographs of liquid crystalline DNA. The photomicrograph in Figure 7(a) was taken with a 20X plan achromat objective under polarized light with a numerical aperture of 0.40 and photographically enlarged by a factor of 10X. Detail is crisp and focus is sharp in this photomicrograph that reveals many structural details about this hexagonally-packed liquid crystalline polymer. Conversely, the photomicrograph on the right (Figure 7(b)) was taken with a 4X plan achromat objective, having a numerical aperture of 0.10 and photographically enlarged by a factor of 50X. This photomicrograph lacks the detail and clarity present in Figure 7(a) and demonstrates a significant lack of resolution caused by the empty magnification factor introduced by the enormous degree of enlargement.

OLED displays can provide additional information such as Exposure Value. Controls and menus can be very nuanced, allowing the photographer to set stop increments, aperture or shutter priority, and a number of other customizations. The German-made Hedeco Lime II even allows its meter to be recalibrated to suit the photographer. The KEKS KM-Q can actually flip the display upside-down for use on oddball cameras like Rollei 35s with bottom-mounted accessory shoes! But these cool settings are buried in menus and I find myself having to consult the manuals to OLED meters for lesser-used settings since controls for these are less intuitive.

The relationship betweenmagnificationand brightnessis

The intermediate image plane is usually located about 10 millimeters below the top of the microscope body tube at a specific location within the fixed internal diaphragm of the eyepiece. The distance between the back focal plane of the objective and the intermediate image is termed the optical tube length. Note that this value is different from the mechanical tube length of a microscope, which is the distance between the nosepiece (where the objective is mounted) to the top edge of the observation tubes where the eyepieces (oculars) are inserted.

KEKS KM01C, KEKS KM02, and KEKS KM-Q also feature simple feet but come with extra plastic and aluminum feet in different thicknesses to fit various size accessory shoes. The trouble with this approach is that if you want to use one of these meters on multiple cameras, you may have to swap out the foot each time you change cameras. Not only does this feel like a waste of time, but it causes unnecessary wear to the screw threads. You could also revert to using a wedge or tape to secure these meters. In the case of the KEKS KM02, I found that I could mount a foot to either side of the meter so it could be fitted to cameras with opposite layouts without removing either foot. During the writing of this review, KEKS released its own spring-loaded foot that can be purchased separately and should solve some of these issues (if you have them.)

Modern research microscopes are very complex and often have both episcopic and diascopic illuminators built into the microscope housing. Design constrictions in these microscopes preclude limiting the tube length to the physical dimension of 160 millimeters resulting the need to compensate for the added physical size of the microscope body and mechanical tube. This is done by the addition of a set of parallelizing lenses to shorten the apparent mechanical tube length of the microscope. These additional lenses will sometimes introduce an additional magnification factor (usually around 1.25-1.5X) that must be taken into account when calculating both the visual and photomicrographic magnification. This additional magnification factor is referred to as a tube factor in the user manuals provided by most microscope manufacturers. Thus, if a 5X objective is being used with a 15X set of eyepieces, then the total visual magnification becomes 93.75X (using a 1.25X tube factor) or 112.5X (using a 1.5X tube factor).

Perhaps the smartest meters to buy if you want to maintain the most compatibility across numerous camera types are the AstrHori XH-2, Reveni Labs Light Meter Mk.2, or KEKS KM-Q with the new foot. Because these meters are not much wider than the standard accessory shoe and their feet are spring-loaded, they should fit pretty much anything without adjustment.

which objective lensisusedwhenviewing bacteria?

The Hedeco Lime II is the only current OLED meter that takes a replaceable CR2032 button cell battery. It also has a unique feature to conserve electricity – the display actually dims automatically in lower light. If you prefer an OLED with a long-lasting, replaceable battery, this meter’s for you.

Photons falling onto a semiconductor material can be divided into three groups based on their energy compared to that of the semiconductor band gap.

This calculator will calculate typical beam intensity min/max ranges for an ILT Light Measurement System you may be interested in purchasing.

Accessory shoe light meters are intended to be mounted to cameras or can be handheld or worn on a lanyard or wristband. They usually take 30 to 40° angle center-weighed reflected light readings and have been manufactured using a number of different information displays including swing needle, LCD, LED, and most recently, OLED panels. They have been powered by everything from solar selenium cells to mercury, alkaline, silver oxide, lithium, and rechargeable lithium batteries.

A simple microscope or magnifying glass (lens) produces an image of the object upon which the microscope or magnifying glass is focused. Simple magnifier lenses are bi-convex, meaning they are thicker at the center than at the periphery as illustrated with the magnifier in Figure 1. The image is perceived by the eye as if it were at a distance of 10 inches or 25 centimeters (the reference, or traditional or conventional viewing distance).

Why does resolutiondecreaseasmagnificationincreases

Rolleiflex-style twin lens reflex cameras locate their accessory shoes on the side. I didn’t find a single meter that did not fit the side mount of my Yashica A. Since the camera is larger, the size and form factor of the meter are of much less concern than it is on a 35mm rangefinder. However, the Yashica’s accessory shoe is attached to the camera reverse standard 35mm cameras, meaning that the meter must be slid into the front of the shoe with the stop that prevents it from sliding out located towards the back of the camera. This is where the otherwise smart spring-clip feet of the DOOMO and AstrHori meters met a problem. I had to reverse mount the foot of these meters in order to install them on the Yashica. But all the other meters slip in fine, though some, like the Voigtländer VCII, require a bit of tape or cardboard to hold them in place.

It's a high powered LED cluster, you need to power it with 9-12V and 100mA of current, the metal body acts as a heat sink. Then, installation is a breeze.

It’s convenient to use an accessory light shoe meter that is powered by the same button cell battery as most of our metered classic cameras. The Voigtländer VCII is the only current model that uses two common A76/LR44 type silver oxide batteries. Not only is this convenient but it guarantees that the exact specification battery will likely continue to be widely available for years to come. The other meters that use disposable batteries employ a CR1632 or CR2032, for which I don’t have any other camera equipment that is compatible.

But with OLED you have a choice. In fact, the KEKS KM-Q is the only model of accessory light meter that you can actually order a top-mounted display or rear-mounted version. Other OLED models situated the display on top or in the rear only.

Nikon F and F2 cameras, however, do not feature their accessory shoe atop their prism heads. Rather, Nikon made removable shoes that fit onto the film rewind crank assembly. Smartly, DOOMO sells its version of this removable shoe.

The eyepiece or ocular, which fits into the body tube at the upper end, is the farthest optical component from the specimen. In modern microscopes, the eyepiece is held into place by a shoulder on the top of the microscope observation tube, which keeps it from falling into the tube. The placement of the eyepiece is such that its eye (upper) lens further magnifies the real image projected by the objective. The eye of the observer sees this secondarily magnified image as if it were at a distance of 10 inches (25 centimeters) from the eye; hence this virtual image appears as if it were near the base of the microscope. The distance from the top of the microscope observation tube to the shoulder of the objective (where it fits into the nosepiece) is usually 160 mm in a finite tube length system. This is known as the mechanical tube length as discussed above. The eyepiece has several major functions:

While the Reveni Labs Light Meter Mk.2 is easily the smallest meter available, one may find its diminutive controls and screen problematic, which is probably why most of the accessory shoe light meters on the market follow a rectangular format.

Subsets of the wavelength range are employed by instruments with detectors and energy sources appropriate for obtaining spectra in their particular range. The ...

The distance from the center of the convex lens to the focal plane is know as the focal distance. (For an idealized symmetrical thin convex lens, this distance is the same in front of or behind the lens.) The image of our giraffe now appears at the focal plane (as illustrated in Figure 2). The image is smaller than the object (the giraffe); it is inverted and is a real image capable of being captured on film. This is the case for the camera used for ordinary scenic photography.

Now we will describe how a microscope works in somewhat more detail. The first lens of a microscope is the one closest to the object being examined and, for this reason, is called the objective. Light from either an external or internal (within the microscope body) source is first passed through the substage condenser, which forms a well-defined light cone that is concentrated onto the object (specimen). Light passes through the specimen and into the objective (similar to the projection lens of the projector described above), which then projects a real, inverted, and magnified image of the specimen to a fixed plane within the microscope that is termed the intermediate image plane (illustrated in Figure 6). The objective has several major functions:

Care should be taken in choosing eyepiece/objective combinations to ensure the optimal magnification of specimen detail without adding unnecessary artifacts. For instance, to achieve a magnification of 250X, the microscopist could choose a 25X eyepiece coupled to a 10X objective. An alternative choice for the same magnification would be a 10X eyepiece with a 25X objective. Because the 25X objective has a higher numerical aperture (approximately 0.65) than does the 10X objective (approximately 0.25), and considering that numerical aperture values define an objective's resolution, it is clear that the latter choice would be the best. If photomicrographs of the same viewfield were made with each objective/eyepiece combination described above, it would be obvious that the 10x eyepiece/25x objective duo would produce photomicrographs that excelled in specimen detail and clarity when compared to the alternative combination.

Whenyou switch to highermagnificationwhatshouldyou do to thelightintensity

Therefore, rather than being a technical evaluation, this article will be more of a survey of available accessory shoe light meters with recommendations for types of photography and particular cameras for which each meter is best suited.

If this sounds silly, there are solutions! DOOMO, Hedeco, KEKS, and Reveni also sell various accessories that facilitate mounting their light meters in unusual, but useful, ways. This includes right-angle-mounting shoes for TLRs and even stick-on shoes for cameras such as Hasselblad medium format SLRs that feature no accessory shoe. Or even Hasselblad and Rollei/Yashica lens hoods with accessory shoe mounts. There are also double accessory shoes and even wristbands, rings, and lanyards for wearing your light meter. Hedeco and Reveni’s solutions are 3D printed plastic while DOOMO and KEKS’ solutions are made of metal. Click on each manufacture’s name in this section for a linkback to their inventive accessory lists.

To understand how the microscope's lenses function, you should recall some of the basic principles of lens action in image formation. We will now review several different imaging scenarios using a simple bi-convex lens:

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Only days before I finalized this review, another meter that I wanted to love, the AstrHori AH-M1 broke, was discontinued and has been replaced with the AstrHori XH-2. I managed to do an ad-hoc repair of the AH-M1 but can’t recommend it due to this failure. I communicated this to AstrHori, who has been very friendly and communicative. They supplied me with an XH-2, which is very similar to the AH-M1 internally and build quality-wise. I mention the AH-M1 because this product change happened pretty recently and the AH-M1 is still available new from some distributors. But if you like the AstrHori OLED panel, clicked control wheel, and brass construction, consider the XH-2 instead.

Ultraviolet lamp, device for producing electromagnetic radiations in the wavelengths between those of visible light and X-rays.

AstrHori AH-M1 and XH-2 (:30sec), DOOMO Meter S (:30sec), Hedeco Lime I & II (8hrs :20min), KEKS KM01C (:30sec), KEKS KM02 (:30sec), KEKS KM-Q (:30sec)

The downside to brass accessory shoe meters, however, is the weight. They are tiny but very dense and add considerable weight to your camera. Aluminum, which all but the AstrHori and Reveni come in, is a better option if you want a lightweight package or are using a silver-colored camera body. I do fear their durability in the event of an impact though.

This case also describes the functioning of the now widely used infinity-corrected objectives. For such objectives, the object or specimen is positioned at exactly the front focal plane of the objective. Light from such a lens emerges in parallel rays from every azimuth. In order to bring such rays to focus, the microscope body or the binocular observation head must incorporate a tube lens in the light path, between the objective and the eyepiece, designed to bring the image formed by the objective to focus at the plane of the fixed diaphragm of the eyepiece. The magnification of an infinity-corrected objective equals the focal length of the tube lens (for Olympus equipment this is 180mm, Nikon uses a focal length of 200mm; other manufacturers use other focal lengths) divided by the focal length of the objective lens in use. For example, a 10X infinity-corrected objective, in the Olympus series, would have a focal length of 18mm (180mm/10).

The film photography market has been inundated with new accessory shoe light meters for the last several years. Some are revisions of previous models with lower price points and slight changes. Several are completely new and unique designs. Choosing which model is right for your particular application can be overwhelming.

Dec 14, 2021 — Luminance is measured in candela per square meter (cd/m²). It denotes how much light is reaching an object, along with the amount of light ...

Both the AstrHori AH-M1 and XH-2 are made of brass. TTArtisans makes the first version of their meter in brass and DOOMO offers both the Meter D and Meter S in black painted brass.

We’ve covered a lot of ground since the top of this article where I mentioned that you might be overwhelmed with all the accessory shoe light meter choices on the market. I couldn’t discuss every nuance about every product here but I have tried to condense months, and years in some cases, of experience with each of these meters into a concise and useful guide.

Both the DOOMO Meter D and TTArtisans Meter are available in superior brass construction and have a more squared-off shape making them a little more cosmetically attractive, and even more durable than the unspecified metal and plastic construction Voigtländer VCII on which they are based.

What meters work best in bright sun may not be so great at night. While LEDs on two-dial meters can be seen in the dark, their exposure numbers cannot. While numbers on the Reflx Lab Light Meter are seen on an LCD panel, it’s not backlit so the meter is of no use after sunset either. The EV ranges of all these meters are greater than their low light visibility, so one could paint the inscribed numbers of the DOOMO Meter D or Voigtländer VCII with glow paint or shine a flashlight onto them, but these solutions aren’t as easy or elegant as simply choosing an OLED meter for concerts and other night time photography.

What I can say about the DOOMO Meter S specifically is that I’ve owned it for over a year and use it a few days out of each month but only recently did I have to recharge it – very good for an OLED meter. If battery life is a priority though, I am convinced that the Voigtländer VCII is your best bet.

How doeslightintensity affect resolution

LED meters like the DOOMO Meter D and Voigtländer VCII don’t have any of these features but are, by the same token, easier to learn and can be used more intuitively and quickly.

For a healthy combination of petite form factor and control, the Hedeco Lime II rivals the Reveni in having the smallest OLED meter available. Its size is flattened into a little “pizza box” shape that greatly reduces protrusion from the camera. Accessory shoe meters increase the height of the camera they’re mounted to. This can make putting the camera in a bag difficult or tight unless you remove the easily misplaced meter each time. With the Hedeco Lime II mounted, cameras fit almost as well into my camera bags as if no meter were mounted. The Lime II looks very sleek also.

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Eyepieces, like objectives, are classified in terms of their ability to magnify the intermediate image. Their magnification factors vary between 5X and 30X with the most commonly used eyepieces having a value of 10X-15X. Total visual magnification of the microscope is derived by multiplying the magnification values of the objective and the eyepiece. For instance, using a 5X objective with a 10X eyepiece yields a total visual magnification of 50X and likewise, at the top end of the scale, using a 100X objective with a 30X eyepiece gives a visual magnification of 3000X.

Finally, the 3D printed plastic body and controls of the Reveni Labs Light Meter Mk.2 do not interest me because material and craftsmanship are among the reasons that I enjoy using vintage film cameras. Reveni’s products just aren’t a match for me personally. If you’re not put off by 3D-printed plastic, I certainly encourage you to check out this Canadian manufacturer’s extensive and creative offerings.

There are just three two-dial LED meters on the market right now and their differences are subtle. The only thing that’s not subtle is the proven track record of the Voigtländer VCII which has been produced for over a decade and has demonstrated infallible reliability for photographers in this time. I’ve seen some very heavily abused VCII’s but I can’t remember ever having seen a copy that doesn’t work. Mine has been in regular use for about ten years without issue. This might make it seem like a slam dunk choice, but not only do the DOOMO Meter D and TTArtisans Meter & Meter II cost less than half the price of the VCII, they add a few welcomed changes.

Many reviews belabor the question of accuracy of accessory shoe light meters when compared to handheld, or other built-in light meters. However, most variance can be accounted for in product parameter differences and can be accommodated with intentional use or even adjusted for some meters. Insofar as each model that I’ve tested, currently available accessory shoe light meters are all reasonably accurate and in agreement with one another within about 1 stop or closer in various lighting conditions. What differs more and I think deserves more consideration is the specific form factor of each light meter.

About the author: Johnny Martyr is an East Coast film photographer. The opinions expressed in this article are solely those of the author. After an adventurous 20-year photographic journey, he now shoots exclusively on B&W 35mm film that he painstakingly hand-processes and digitizes. Choosing to work with only a select few clients per annum, Martyr’s uncommonly personalized process ensures unsurpassed quality as well as stylish, natural & timeless imagery that will endure for decades. You can find more of his work on his website, Flickr, Facebook, and Instagram.

With a top-mounted display, candid and casual photography is made that much easier because reading exposure does not require lifting the camera to the eye and calling attention to the fact that a photo is about to be taken.

Two-dial type meters like the DOOMO Meter D, TTArtisans Meter & Meter II, and Voigtländer VCII only go down to one-second shutter speeds. If you’re doing something like astrophotography and need extended shutter times, you should use an OLED meter not only for the wider metering range but also so you can actually see the display in the dark, unlike the Reflx Lab Light Meter, which goes down to 30-second exposures but doesn’t have a lit screen. Most OLED meters only go down to 30 seconds. However, the Reveni Labs Light Meter Mk.2 goes down to one full hour and the Hedeco Lime II can measure to an unbelievable 8 hours and 20 minutes! I’m not sure what anyone needs that for by hey, there you go! The maximum shutter times for the others are listed below:

There are a slew of vintage and modern accessory shoe meters that I haven’t personally tested. Obviously, tracking down every vintage meter in working condition would be difficult and arguably not as useful as currently available meters for general purposes. There are also a number of nameless, modern Chinese accessory shoe meters available only on sites like eBay, Temu, and similar. I don’t get the impression that these devices are manufactured by fully scaled businesses and I’ve seen dicey reviews of a few, so I would not recommend them based on this alone.

An easy way to understand the microscope is by means of a comparison with a slide projector, a device familiar to most of us. Visualize a slide projector turned on its end with the lamp housing resting on a table. The light from the bulb passes through a condensing lens, and then through the transparency, and then through the projection lens onto a screen placed at right angles to the beam of light at a given distance from the projection lens. The real image on this screen emerges inverted (upside down and reversed) and magnified. If we were to take away the screen and instead use a magnifying glass to examine the real image in space, we could further enlarge the image, thus producing another or second-stage magnification.

I have used and loved the Voigtländer VCII longer than any other but the low light capability of OLED meters tempted me to move on and compile this article. Surprisingly, I found that I really don’t like the complication of any of the newer OLED designs, clever and useful though they are. I greatly prefer the quick, intuitive two-dial type meter where all potential settings can be seen and understood at a glance and adjusted effortlessly. The DOOMO Meter D keenly addresses all of the minor concerns I have with the Voigtländer VCII while adding all brass construction as an option and a much lower cost. It’s become my most-often used accessory light meter.

When I began this article, I was of the opinion that all accessory shoe meters available today are quality products. I wanted to give an unbiased opinion of how best to use each of them, more so than claiming one is inherently better than another. Unfortunately, it turned out that there are a few meters that I just cannot recommend.

The object is brought to twice the focal distance in front of the lens. The image is now two focal lengths behind the lens as illustrated in Figure 4. It is the same size as the object; it is real and inverted.

Vintage accessory shoe light meters featured top-mounted displays. And so do modern two-dial LED meters like the DOOMO Meter D, TTArtisans Meter & Meter II, and Voigtländer VCII.

Conversely, the TTArtisans Meter & Meter II are probably the largest accessory shoe meters available right now. The older TTArtisans Meter is made of thick gauge brass and is not only the largest but, heaviest meter I tested. The newer Meter II is made of aluminum and isn’t as long but is still taller than similar meters. They seem most at home on a TLR or other larger-bodied camera but are comically disproportionate on something like a half-frame camera, screw-mount Leica, or Voigtlander Perkeo. Despite their size, the TTArtisans meters don’t offer any larger display or controls than the similarly designed DOOMO Meter D or Voigtländer VCII.

Perhaps the first matter of concern for many photographers is whether a given meter is going to physically fit their particular camera(s). Nearly every contemporary accessory shoe light meter available new today features a foot that can be unscrewed from the meter body and repositioned to fit different cameras. The only three that do not have a removable, adjustable foot are the AstrHori XH-2, KEKS KM-Q, and Reveni Labs Light Meter & Mk.2 because they don’t actually need to be repositioned.

Light from an object that is very far away from the front of a convex lens (we will assume our "object" is the giraffe illustrated in Figure 2) will be brought to a focus at a fixed point behind the lens. This is known as the focal point of the lens. We are all familiar with the idea of a "burning glass" which can focus the essentially parallel rays from the sun to burn a hole in piece of paper. The vertical plane in which the focal point lies is the focal plane.

The KEKS KM-Q is only slightly larger than the Reveni but its four buttons are not crammed together in one cluster, rather they’ve been relocated to the sides of the meter housing and they are larger than the Reveni. All KEKS meters feature professional-looking and feeling aluminum bodies and controls so the KM-Q is my personal favorite alternative to the Reveni.

I wanted to love the TTArtisans brass meter as an affordable Voigtländer VCII alternative with higher quality materials. The TTArtisans brass meter has a beautiful finish and feels bombproof but is very large compared to similar meters. In practice, its size is tolerable but the real problems are that the ISO dial is easily changed inadvertently, and the LED is extremely faint in daylight. Additionally, the replaceable CR2032 battery died in less than a year of fairly conservative use.

When you look into a microscope, you are not looking at the specimen, you are looking at the image of the specimen. The image appears to be "floating" in space about 10 millimeters below the top of the observation tube (at the level of the fixed diaphragm of the eyepiece) where the eyepiece is inserted. The image you observe is not tangible; it cannot be grasped. It is a "map" or representation of the specimen in various colors and/or shades of gray from black to white. The expectation is that the image will be an accurate representation of the specimen; accurate as to detail, shape and color/intensity. The implications are that it may well be possible (and is) to produce highly accurate images. Conversely, it may be (and often is) all too easy to degrade an image through improper technique or poor equipment.

A very thoughtful and useful upgrade on the DOOMO Meter D and TTArtisans Meter & Meter II is the simple addition of + and – signs on the meter read-out. When you’re jumping around from different meters, the VCII’s basic pointing triangles can be confusing (to me anyway). I long ago applied a small + – label to my VCII but it’s nice that the DOOMO and TTArtisans alleviate any guessing out of the box.

A question that many people have asked me while I’ve been testing these meters is what the life expectancy and ability to replace the battery inside rechargeable meters. Unfortunately, most of these meters haven’t been around long enough for anyone to do extended-use testing.

A few of the currently available accessory shoe light meters are strikingly similar to one another so I wanted to do a quick comparison between these.

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OLED displays can be very small but this of course also reduces screen and information size. I found the DOOMO Meter S OLED panel to be the most optimal balance of small size and large, easy-to-read information with the AstrHori AH-M1 and AstrHori XH-2, which share the same panel, tied for a very close second.

Total magnification is also dependent upon the tube length of the microscope. Most standard fixed tube length microscopes have a tube length of 160, 170, 200, or 210 millimeters with 160 millimeters being the most common for transmitted light biomedical microscopes. Many industrial microscopes, designed for use in the semiconductor industry, have a tube length of 210 millimeters. The objectives and eyepieces of these microscopes have optical properties designed for a specific tube length, and using an objective or eyepiece in a microscope of different tube length will lead to changes in the magnification factor (and may also lead to an increase in optical aberration lens errors). Infinity-corrected microscopes also have eyepieces and objectives that are optically-tuned to the design of the microscope, and these should not be interchanged between microscopes with different infinity tube lengths.

All currently available accessory shoe light meters are very small. But whenever a photographer is mounting accessories to the limited real estate of a camera, every little bit counts. You want something small enough to fit neatly on your camera but not so small that you have difficulty controlling and reading it.

The KEKS KM-Q goes into a power save sleep but takes a bit longer than I’d like to wake up. Because it is such a small meter, it does not display the ISO at all times, instead, it shows the ISO for a prolonged time while starting up which I find annoying to sit through nearly every time I want to take a reading. So while the KM-Q is good for universal fit, it is not ideal for speedy use.

Because the ISO dial tends to slip out of place on the TTArtisans Meter, I keep a bit of tape on it to hold it in place. And as mentioned the LEDs aren’t as bright as the Voigtländer VCII and DOOMO Meter D. The TTArtisans Meter & Meter II also fail in that the exposure settings appear to be printed on, rather than engraved into the dials. With wear, these could become unreadable. The Voigtländer VCII and DOOMO Meter D numbering is engraved into the metal and should be legible even if the paint or surface of the dials are rubbed down.

I hope that you’ll be able to find the right meter, or meters, for your particular applications without having to spend all the time that I have in coming to these conclusions. Surely there are some uses that I might have missed, but I invite readers to provide more insight in the comments section and help inform everyone who’s interested in adding accessory shoe light meters to their go-to gear list.

The factor that determines the amount of image magnification is the objective magnifying power, which is predetermined during construction of the objective optical elements. Objectives typically have magnifying powers that range from 1:1 (1X) to 100:1 (100X), with the most common powers being 4X (or 5X), 10X, 20X, 40X (or 50X), and 100X. An important feature of microscope objectives is their very short focal lengths that allow increased magnification at a given distance when compared to an ordinary hand lens (illustrated in Figure 1). The primary reason that microscopes are so efficient at magnification is the two-stage enlargement that is achieved over such a short optical path, due to the short focal lengths of the optical components.

Up until now, most of my comments revolve around 35mm rangefinders. There’s probably not a lot of need to discuss how these meters fit on 35mm SLRs because let’s face it, they all look totally ridiculous mounted atop a pentaprism. But from a functional standpoint, any of these meters will fit and allow room to work the controls of the camera when mounted to an SLR. So for 35mm SLRs, you are pretty much free to choose whatever meter you like!

The range of useful total magnification for an objective/eyepiece combination is defined by the numerical aperture of the system. There is a minimum magnification necessary for the detail present in an image to be resolved, and this value is usually rather arbitrarily set as 500 times the numerical aperture (500 × NA). At the other end of the spectrum, the maximum useful magnification of an image is usually set at 1000 times the numerical aperture (1000 × NA). Magnifications higher than this value will yield no further useful information or finer resolution of image detail, and will usually lead to image degradation, as discussed above. Exceeding the limit of useful magnification causes the image to suffer from the phenomenon of empty magnification (see Figures 7 (a) and (b)), where increasing magnification through the eyepiece or intermediate tube lens only causes the image to become more magnified with no corresponding increase in detail resolution. Table 1 lists the common objective/eyepiece combinations that lie in the range of useful magnification.

So more than if the meter foot is adjustable, what photographers should consider is if their cameras feature any kind of tensioning mechanism on the accessory shoe and if the meter they’re interested in also does.

Since the image appears to be on the same side of the lens as the object, it cannot be projected onto a screen. Such images are termed virtual images and they appear upright, not inverted. Figure 1 presents an illustration of how a simple magnifying lens operates. The object (in this case the subject is a rose) is being viewed with a simple bi-convex lens. Light reflected from the rose enters the lens in straight lines as illustrated in Figure 1. This light is refracted and focused by the lens to produce a virtual image on the retina. The image of the rose is magnified because we perceive the actual size of the object (the rose) to be at infinity because our eyes trace the light rays back in straight lines to the virtual image (Figure 1). This is discussed in greater detail below.

The last case listed above describes the functioning of the observation eyepiece of the microscope. The "object" examined by the eyepiece is the magnified, inverted, real image projected by the objective. When the human eye is placed above the eyepiece, the lens and cornea of the eye "look" at this secondarily magnified virtual image and see this virtual image as if it were 10 inches from the eye, near the base of the microscope.

OLED-type meters like the AstrHori AH-M1, AstrHori XH-2, DOOMO Meter S, KEKS KM01C, KEKS KM02, KEKS KM-Q, and Reveni Labs Light Meter Mk.2 use built-in rechargeable batteries more or less out of necessity. I’ve been using the DOOMO Meter S intermittently for about a year and only recently had to plug it in. I have not used the others long enough to require their first recharge.

Earlier cameras such as screw mount Leica, Contax/Zeiss, Konica, and Kodak Retina rangefinders as well as Yashica TLRs and Voigtlander folders and many others, feature a simple “cold shoe” that does not contain any kind of ball bearings or spring clips for tensioning and holding different accessories securely. Therefore the Reflx Lab Light Meter, TTArtisans Meter & Meter II and Voigtländer VCII with their simple foot may require a cardboard wedge or bit of tape to hold the meter onto these cameras.

The object is now situated between one and two focal lengths in front of the lens (shown in Figure 5). Now the image is still further away from the back of the lens. This time, the image is magnified and is larger than the object; it is still inverted and it is real. This case describes the functioning of all finite tube length objectives used in microscopy. Such finite tube length objectives project a real, inverted, and magnified image into the body tube of the microscope. This image comes into focus at the plane of the fixed diaphragm in the eyepiece. The distance from the back focal plane of the objective (not necessarily its back lens) to the plane of the fixed diaphragm of the eyepiece is known as the optical tube length of the objective.

When I requested a product sample of the updated TTArtisans Mark II Meter, I was told by a representative that “actually the brass light meter is better than [the] regular light meter.” After an attempt to bridge the communication problem that seemed to be occurring with the Chinese-based company, I was still unable to secure a test sample of the TTArtistans Meter II on the grounds that the older meter that I purchased, which isn’t that great, is better than the latest version.