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Asphericmeaning

Thanks for in-depth articles. I do have Lee big stopper and looking for GND filter (Hard edge), however I am not able to find anything with glass and most of the brand out there are offering only Resin and not glass (I am only looking at Rectangular GND). Can you provide your input on this.

For the sharpness test, we used the Nikon 105mm f/1.4E ED, which we are in the process of evaluating for an upcoming review. The lens was mounted on the Nikon D810 and shot in Mirror Lock Up mode, with EFCS (Electronic Front Curtain Shutter) enabled, as detailed in our how to reduce camera shake on a tripod article. While the numbers are not yet final (only one sample was tested with a high-resolution chart at a very close distance, which can skew mid-frame and corner numbers), you can see that the lens looks absolutely amazing, almost Zeiss Otus-like in terms of center sharpness – definitely one of the sharpest Nikon prime lenses we have ever tested.

Dear Nasim I am not a professional photographer from St.Petersburg, Russia, I would call myself an amateur I have used Lee Filters 100 mm system on my Nikon D800+77 mm lenses since 2012. Last Saturday I decided to buy a 150 mm system for my Nikon 14-24 mm 2.8 lens, and what made me choose the Lee SW150 system was your comment to avoid using a polarizer on wide -angel lenses, as well. So I came to think that rotating CPL feature wouldn’t tip the balance to the NiSi system, moreover, given the fact that the Nisi site is very inferior to the site of Lee Filters in terms of marketing and selling. I would say the NiSi website is underdeveloped. The point of comment was that the NiSi system’s rotating polarizing filter feature does not necessarily mean its superiority for wide-angel systems. But I have to admit that I have started to regret my choice of the Lee Filters system for Nikon 14-24- mm after your NiSi systems review. I should have read it before I made my choice.

AsphericLenses price

The graphs above show a very typical situation when using resin filters – there is a definite and visible drop in sharpness on high-resolution cameras, even at 36 MP. As you can see, Lee’s two stop 0.6 GND (Graduated Neutral Density) filter had a pretty dramatic drop of sharpness, almost 17.5% lower in center sharpness compared to not using a filter and around 15.8% lower in center sharpness compared to NiSi’s glass filter.

An optical short-pass filter only lets light pass below a certain wavelength, the so-called cut-off wavelength | More in the Light Source Glossary.

Once upon a time when I had my first 35 mm Camera, a Kodak Retinette 1A, wow that was something in those days of 120 and 620 film format and 5×4 press cameras. I obtained glass Wratten filters, both CT and CC in a glass mounted “clip on” stainless ring which clipped on to the end of the lens they were made for the Graflex 5×4 as well. They seemed to disappear very quickly with the advent of Hoya and other brands coming on the market as screw in filters. All mine were in a leather case each filter separated by leather lined with felt. At that time they cost me 37 Pound which was quite a lot of money as my pay packet was 10.12.6 (Ten pound twelve and six pence) a week. It was easy in the field, and there were many fields, seldom dropped one easy to “push on” and a gentle twist and pull would remove it then put it back into the case. Screwing a filter in takes a lot longer, maybe the “new” 100mm ester filters could be made of glass if the holders were made so they would not slip out. A rethink on this I think, or maybe I’m just an old codger bordering on dynasaur.

Define aspheric lensvs asphericallens

Aphakic lenses use aspherics because plus power lenses higher than +8.00 are outside of the Tersching ellipse and do not have a best form curve. This means that in order to provide the best vision the lens designer has no choice but to use aspherics. Usually you will find that the aphakic lens not only uses asphericity to optically improve the performance of the lens, but often the lens uses again deformed conicoids to provide cosmetic appeal to the lens as well since often times high plus powers will be thick.

Great tool to test if lenses are polarized.

What types of filters do you personally use? Resin or glass? Have you tried both to see what is practical in the field? Would love to hear your thoughts in the comments section below!

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I can confirm your results. That’s why I use the Benro Master filters made of glass. In combination with a well thought filter holder (polarizer in a special ring in the holder itself) a perfect for combination me.

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Actually, the numbers were even lower when I initially mounted resin filters. Due to changes in optical path when using resin filters, I actually had to refocus my setup and see if I can get better numbers. I was able to get higher numbers in the center of the frame and due to the change of plane of focus, the change did affect mid-frame numbers as well, which is why they show up a little higher in comparison to not using a filter at all.

Aspheric lensglasses

As you can see, the NiSi 10 stop ND filter performed really well compared to the HiTech resin filter, which actually caused quite a bit of damage – practically a 30% drop in sharpness! So keep this in mind if you want to do long exposure photography. Looks like glass is the way to go not only if you want to preserve original colors (no color cast), but also if you want to keep the resolving power of your lens.

Aspheric lensbenefits

We also decided to run another test to compare two 10 Stop ND filters from NiSi (glass) and HiTech (resin). Aside from serious color cast issues pointed out in our NiSi Filter System review, we saw a pretty dramatic drop in sharpness when comparing NiSi to HiTech filters. Take a look at the MTF numbers below:

Aspheric lenses are defined as lenses that are non-spherical. This non spherical surface encompasses all kinds of lenses from aspheric, atoric, progressive, and aphakic. So if all these lenses fall in the definition of an aspheric lens, how do we further define and differentiate aspheric lenses in all their forms.

We stopped down the lens to f/5.6 to yield maximum sharpness (although MTF numbers at f/4 look even more impressive in some cases) and we used a few different focusing techniques to yield the best possible performance without any filters, while a NiSi filter holder was already attached to the lens. Once maximum resolution numbers were achieved, we mounted one filter at a time, without touching the focusing ring.

Asphericallensphotography

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Hi. A little detail caught my attention when I bought a complete Cokin filter set. All made with c39 resin optics. Then I started thinking why not glass, I came across the article on your site. The article was very revealing to me. I realized that the square filters must be glass. LEE filters were also very expensive for me. Thank you I saved my money from wasting.

Resin filters definitely have their own advantages – they handle great in the field and if you drop them on a hard surface, they do not break like glass does. They don’t shatter under pressure, since they have the flexibility to bend. However, they are quite prone to scratches and even moderate use of resin filters can introduce small scratches all over the filter. While scratches don’t do additional damage to your images in terms of sharpness, they certainly can reduce contrast and potentially introduce more artifacts to your images when shooting against bright sources of light (in the form of ghosting and flare).

This expansion allows the shape to be manipulated to varying degrees as it gets further from the axis without directly affecting the axis. This expansion can also be used to define a more simple conic section by setting the B, C, D, and E variable to 0, therefore only the a value remains and defines the conic.

Keep in mind that these tests were performed with a 36 MP camera. If I were to show you difference with 42 or 50 MP cameras, the differences would be even more apparent. Please don’t try to view these images on a small mobile device / tablet, or a large super high-resolution screen, since pixels would be packed too closely together and you would never see any differences. 15% does not look like a big number for sure, but if you look closely at edge detail, the differences are definitely there. Now if those differences are too small for you to care about, then by all means, forget about the existence of this article! However, if you do want the best edge detail your camera can provide for landscape or architectural photography needs, you might want to re-evaluate your setup and potentially look into getting resin filters replaced with glass filters.

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Nasim Mansurov is the author and founder of Photography Life, based out of Denver, Colorado. He is recognized as one of the leading educators in the photography industry, conducting workshops, producing educational videos and frequently writing content for Photography Life. You can follow him on Instagram and Facebook. Read more about Nasim here.

Generally aspheric in the ophthalmic industry defines a lens surface that varies slightly from a spherical surface. This variation is known as the eccentricity of the lens and can further defined as conic sections. Sections of a cone represent various curves that are used in ophthalmic surfaces, for instance circle, ellipse, parabola, and hyperbola.

Personally, I am planning to start using glass filters from now on. However, in case I do lose a filter in the field, I am planning to bring my Lee filters along, just in case :)

I travel with large glass filters all the time, and have never had any problems with them. A little bubble wrap, and a small plastic box from an art supply store is all one needs. Not quite sure what the all the fuss is about, concerning traveling with glass filters.

After testing out my Lee filter, I decided to mount HiTech’s 0.6 GND as well and see what it would yield. As you can see, although its performance looks a tad better, overall, it is really not much different compared to Lee. Center performance drops by roughly 15%, which is certainly not a small number – that’s practically worse than using a cheap circular filter in front of your lens.

At the same time, take a look at what happens when a resin filter is mounted on the camera. I have been using Lee and HiTech filters for years and previously, I never really noticed much loss of sharpness in my images when using lower resolution cameras. After I started using high-resolution cameras such as the Nikon D810, Sony A7R II and Canon 5DS R, I did start noticing differences in sharpness in my images. Not to the point that would make me not want to use filters, but definitely to the point where I started wondering if perhaps my filters needed to be replaced.

Nasim, I just found your comparison more or less randomly. Your findings matches my obersvation perfectly by 100%. With the 5DsR, I encountered a noticable loss of sharpness using resin filters (Lee, Singhray) especially when using a longer focal length. I switched to NiSi in late 2015 and the results were good again. Regards, Michael

I do not enjoy traveling with rectangular filters because of their size and bulk, including the filter holders and since landscape photography is not my primary intent when traveling. Instead, I carry a few round glass filters protected by stack caps. I carry a set of 77mm filters: B+W 10-stop, 2-Heliopan GND (one hard and one soft) along with a B+W full grad and a pair of B+W polarizing filters (77mm and 67mm). I use the 77mm grads with a 67mm adapter for my 70-200mm f/4L IS lens and I have 67mm and 77mm polarizers since I often shoot with two cameras, one using a lens that takes 67mm filters and one that takes 77mm filters. This is not the ideal kit but, I have found that on trips, when I took my Lee filter setup, I seldom went to the trouble of setting up that system since my primary intent is not landscape photography. Using round filters is quicker and easier… I simply crop when I want the horizon at other than mid-way in the frame. I WISH HOWEVER: that some filter company would offer a set of two GND round filters in which the dark portion covered 1/3 of one of the filters and 2/3 of the other. Carrying an extra two filters would not add any appreciable weight or bulk to my travel kit, yet would allow me to come a lot closer to ideal framing of the horizon (rule of thirds) when using a round filter – without as much cropping involved…

Asphericlenses vs spherical

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Landscape photographers often deal with the dilemma of choosing between different types and brands of neutral density and graduated neutral density filters for use in high-contrast situations such as sunrise and sunset, where their cameras might not have enough dynamic range to be able to capture the entire scene. While we are not going to go over each and every brand to see which one performs better, we do want to show the difference in sharpness between glass and resin filters. For this particular test, we used three 0.6 (2 stop) filters from three different manufacturers – NiSi (glass filter), Lee (resin) and HiTech (resin). The latter two are probably the two brands that are used the most among photographers in the field.

I use Olympus EM5 mark II micro 4/3 sensor with 12-40 f 2.8 lens. I want to buy hitech filter. But I still confused to chose resin or glass?

In comparison, glass filters are obviously superior in sharpness and they are less prone to scratching. However, they do require better handling in the field, so you must be able to provide good protection for them not only while transporting, but also while using. If you drop a glass filter, unless it lands on grass, you will have to look for a replacement.

As you can see, there is no difference between using a lens with or without a glass filter. And we have shown before in our clear filter tests, if one uses high quality glass in front of a filter, there is no impact on the lens’ resolving power. So it looks like if one uses glass filters similar to the ones from NiSi, one can get maximum sharpness from the camera + lens setup.

Keep in mind that aspherics when referred to in ophthalmics can be placed on both the front or back surface of the lens and as free form technology takes a hold in our industry we will be seeing varying degrees of eccentricity on both the front and the back of all lenses to improve cosmetics and optics.

To get a good idea of what an aspheric looks like, the theorem sin-1(e) gives you the angle at which to tilt a cone to view from above the shape the curve will represent. If you were to take a coffee mug and tilt it by any degree you would see that the shape of the perfectly circular top changes when it is tilted, this same shape represents the curves of the lens. Why are aspheric lenses used? Aspheric lenses are used in their various forms to correct aberrations in a lens that are produced from changes to best form curves. For instance in a CR-39 lens a lens with power -2.75 calls for a 4.63 base lens, if that lens were to be made up in a 6 base the consequences would be that the lens would change power as the wearer were to view further off the visual axis of the lens. This change in power can be compensated for by allowing the form of the lens to vary as it goes further from the axis, this eccentricity would allow the lens to correct the condition in which it was prescribed as well as fit the individual frame or curve necessary to make a cosmetically appealing lens.

Asphericlenses advantages disadvantages

In the previous example we used a power of -2.75 for a CR-39 lens, if we were to give an example of a -2.75 -2.00 sphero-cylindrical lens the best form curve would differ for the two meridians (sphere and cylinder). Using a spherical lens you would have to determine the meridian in which you would want to provide the best base for either, sphere or cylinder, or spherical equivalent and split the error between the two meridians. The solution to this is an atoric lens which can be defined as having differing eccentricities for the separate meridians. This allows the user a wider area of the lens with the correct power and minimal aberrations.

Now you might be wondering, can these differences be seen in images? Let’s take a look at two crops taken from the above-mentioned tests:

Progressive's lenses are a category in and of themselves; however the progression of power is accomplished with the use of asphericity in the corridor to create a lens without power. Progressive lenses differ from many aspheric surfaces because they are not fashioned after conic sections, but would be better defined as deformed conicoids. To get an idea of what a deformed conicoid would look like take a pebble and drop it into a pond, the waves would ripple and the surface could not be defined with a simple curve, but depending on where in the pond you look the curves would vary, this variation could be defined with an expansion of the saggital equation: