Depth of viewcamera

If the different layers in your scene are too close together, there won’t be enough distance between the objects to create any noticeable difference in how much light can be dispersed. In some ways, this will make the objects appear to be on the same plane (or at least in the vicinity) of each other.

Image brightness is directly proportional to the objective NA and inversely proportional to magnification.  Therefore if you had two objectives of the same NA but differed in magnification, for examples the following;

Depth of viewexample

In theory, the intensity of illumination depends on the square of the condenser numerical aperture and the square of the demagnification of the light source image (in effect, the field diaphragm image becomes brighter as it is made smaller, according to the square law). The result is that brightness of the specimen image is directly proportional to the square of the objective numerical aperture as it reaches the eyepiece (or camera system), and also inversely proportional to the objective magnification. Therefore, when examining specimens in transmitted light, changing the objective without altering the condenser affects image brightness in response to changes in numerical aperture and magnification.

It’s also worth noting that when you widen the aperture, you’re letting more light through and therefore need to compensate for exposure by using a faster shutter speed or lower ISO value. If you’re shooting in an ‘auto’ mode, your camera should do this for you.

Different lenses have different maximum apertures. Aperture is measured in f-stop and the lower the f-stop number, the higher the aperture (wider the iris). Therefore an f-stop of 1.8 has a wider aperture than an f-stop of 3.5.

Bokeh is the name for the blur that occurs as a result of a narrow depth of field. It is typically circular because it scatters within the confines of a circular element in the eye or a camera lens called an diaphragm or ‘iris’. The wider the iris, the larger the circles.

The resolving power of the objective is determined by the numerical aperture (not magnification). Numerical aperture also determines the light collecting ability of the objective, the higher the NA the more light the objective can collect and is determined by the function (nSinq, Where n =  immersion media refractive index, and Sinq = angle of the cone of illumination).

Landscape photography typically (but not always) uses a large depth-of-field to capture all of the detail of the landscape, whereas portrait photography usually utilizes shallow depth-of-field to draw focus onto the subject.

Depth offield photography settings

Depth of field can also be used to draw attention to a particular detail in an image – for example the shoelace in a photograph of a boot, or a person’s eyes in a portrait. It increases the contrast in the focus area relative to the areas around it, and our eyes are naturally drawn to areas of high contrast. If you have more than one subject in your shot, you can use depth of field to pull your viewers focus to one in particular.

Depth of field is all about drawing focus onto a particular subject and works in much the same way that the lens in your eye does.

One of the main purposes of depth of field is to create what’s called ‘subject separation’. Bokeh can be used to soften distracting elements in the background or foreground of an image so that the eye is automatically drawn to the subject of choice.

Correction collars are generally used to correct for spherical aberration due to variations in coverslip thickness, temperature, wavelength or for the differing refractive indices of different immersion media.

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The reason that the areas that are out of focus appear blurry is that the precision of the light being captured from these areas is sacrificed to benefit the precision of those you want to look at. This means that the light in these areas becomes scattered – usually in the shape of a circle because of the shape of your iris – the part of your eye that ‘steers’ light onto your retina

Getting your camera down low can offer unique perspectives in any context. When using a shallow depth of field, it can also create a smooth ‘taper’ effect at ground-level that can look really interesting.

Where F(trans) refers to image brightness of a Brightfield illuminated sample, whereas F(epi) refers to the image brightness of a fluorescence or reflected light illuminated sample.

Another way to create a sense of depth in your imagery is with atmospheric effects. We’re talking about things like mist, fog, haze, or dust. These types of effects usually create a subtle ‘diffusion’ of light and reduce the contrast between different layers. The heavier the atmosphere, the stronger the effect and sense of depth. Using atmospheric effects in combination with long lenses can create powerful layering in your images.

Depth of viewvs focus

Depth offield microscope

This excel spreadsheet has two worksheets that let you compare different objectives to determine their relative brightness

While it can be tempting to go out and shoot everything at the highest possible aperture to get that nice ‘creamy’ bokeh, it’s easy to get carried away and forget what you’re trying to achieve.

The aperture of your lens refers to how wide the diaphragm or ‘iris’ in your camera opens. When you open the iris wider (a higher aperture), it increases the radius at which light can disperse when making its way to the sensor. This creates lens blur that’s more pronounced, and as a result, reduces the depth of field.

Shallowdepth offield

Try closing one eye and placing your finger in front of the other. Now focus on your finger, and slowly move it away from your eye whilst staying focused on it. Do you notice how the background slowly comes into focus?

There are different 'grades' of objectives which describe how many colours they are axially corrected for, and how many colours they are spherically corrected for.

Too much depth can make it hard to tell what you’re looking at. Sometimes just a little can achieve the effect you’re looking for – and will preserve some of the context of your scene for viewers to pick up on. The benefit of a wider depth-of-field is also that it’s much easier to keep things in focus – pulling focus on a moving subject is pretty difficult when your depth-of-field only spans a thin sliver of the range.

Longer lenses can be used to bring objects ‘closer together’ in the resulting image, reducing the depth and increasing the implied ‘intimacy’ between them. Wider (or shorter) lenses can be used to make things seem far apart, for example – using a fisheye lens to shoot a long corridor can make it appear to go on almost forever.

A special objective is required that is fitted with a darkened circular ring or groove (phase plate) fitted into the glass near the rear focal plane of the objective as illustrated in Figure 1. In addition, the condenser must also be modified with special annular openings suited to a particular magnification and objective. Phase contrast objectives are segregated into a number of categories depending upon the construction and neutral density of internal phase rings:

The focal length of a lens dictates its field-of-view, i.e. how ‘wide’ it is. For example ‘wide-angle’ and ‘fisheye’ lenses have a wide focal length (usually between 10 and 35mm) and ‘telephoto’ lenses can have focal lengths of anywhere from 80 to 2000mm or more. The longer the focal length, the more ‘zoomed-in’ the image that the lens produces.

As well as creating dimension and context, out-of-focus elements in the foreground can be used to obstruct unsightly elements in the scene, or create more mystery surrounding the context of your subject. Close up elements can create a subtle and unobtrusive effect that slowly tapers off the detail in an area of the image.

In order to allow the microscopist to quickly identify phase contrast objectives, many manufacturers inscribe important specifications, such as the magnification, numerical aperture, tube length correction, etc., on the outer barrel in green letters. This serves to differentiate phase contrast objectives from ordinary brightfield, polarized, DIC, and fluorescence objectives which either use an alternative color code or the standard black lettering.

Moving yourself (or the camera) closer towards the objects in the scene increases the relative distance between the objects themselves when compared with the distance from the camera. This increases the perceived depth and can add more lens blur to background and foreground layers. Similarly, moving the camera further away will reduce the depth of field and make objects seem closer together.

Depth offield photography examples

Most microscope objectives are designed to be used with a cover glass that has a standard thickness of 0.17 millimeters and a refractive index of 1.515, which is satisfactory when the objective numerical aperture is 0.4 or less. However, when using high numerical aperture dry objectives (numerical aperture of 0.8 or greater), cover glass thickness variations of only a few micrometers result in dramatic image degradation due to aberration, which grows worse with increasing cover glass thickness. To compensate for this error, the more highly corrected objectives are equipped with a correction collar to allow adjustment of the central lens group position to coincide with fluctuations in cover glass thickness.

The focal length of your lens can affect depth of field because it affects the apparent distance between you and the objects in your scene. Longer focal lengths tend to have a pronounced depth of field, so using a telephoto lens like an 85mm or 105mm can be a good way to add dimension and depth (providing you use a high enough aperture to make use of it).

Increasing the space between objects increases the depth, and therefore the distance that light has to disperse and create bokeh. However, it’s not always possible to move the elements in your scene, especially if you’re shooting events, documentary, wildlife, or sports. So what else can you do to control depth of field?

The terms F(trans) and F(epi) refer to the light-gathering power of an objective and were calculated according to the following equations:

Some objectives are also "Plan-" objectives, these are flat field corrected, so the image appears flat to both the eyepieces and the detector.

If you’re just getting started in the world of photography and filmmaking, you might have come across the term ‘depth of field’. While it might sound quite complicated, depth of field is actually a fairly simple technique that can add a ton of value to your images. In this article, we’ll cover what depth of field is, how it works, and how to use it creatively in your images.

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Depth of viewcalculator

Depth-of-field may be the most common way to create depth in an image, but it certainly isn’t the only way. You can also use techniques like lens compression, field-of-view, and atmospheric effects. Combining two or more of these techniques can create unique images with lots of dimensionality.

What’s happening here is your eye clamps a ‘focusing range’ around your finger so it can stay focused on it. As you move your finger away, your eye adjusts to move that focusing range with it, meaning the objects in the background are coming closer to the centre of focus.

Not all objectives are made equal! Objectives for microscopes contain lots of very small and delicate lens to both magnify the image, as well as to perform a number of corrections (spherical and chromatic). Two main characterizations of objectives are the magnification and the numerical aperture.

You can also use depth of field to create what’s called ‘layering’. Photographers and cinematographers will often add elements like plants or structural elements as an out-of-focus layer in the foreground. This helps to add dimension to your image, and creates a more immersive perspective for the viewer. Try experimenting with two, three, four, or even five layers to see how it affects your final result.

Lens compression is what happens when you have really ‘zoomed-in’ telephoto lenses. It refers to the ‘squishing’ of elements or layers together so they seem closer together (or farther apart) than they actually are.

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Simply put, depth is the distance from the camera. Depth of field is the portion of that distance or ‘depth’ that is ‘in-focus’. A higher depth of field would see the whole image from foreground to background sharp and in focus, a lower depth would result in blurry backgrounds and blurred elements in the foreground too.