How can I know if a lens can handle a camera's resolution?

Question

For a fashion photoshoot (it is just a fun group photoshoot but I like to take it seriously!) I am thinking about getting real close for some shots and to take pictures with maybe one eye with great makeup or just the lips with great makeup in the frame. So I rented this:

Nikon AF-S VR Micro-NIKKOR 105mm f/2.8G IF-ED

And I myself also have this:

Zeiss 135mm f/2 Apo Sonnar T* ZE

And the camera is a Nikon D-810, so it has 36 megapixels. I want to know which lens to use for this purpose that won't fall apart with that many pixels.

Answer 1

Those two good lenses will handle the resolution, once stopped down to an optimal aperture. This is around F/5.6 on the Nikkor and F/4 on the Zeiss. Do test it out before going to your shoot. 2 stop down from wide-open is a rule-of-thumb, many quality lenses need less.

The most important for your close up shots though is the magnification as you will lose significant resolution if you cannot frame tightly enough and need to crop to your desired composition.

The Nikkor has 1X magnification compared to 0.25X for the Zeiss, so you should use the former.

Answer 2

No, it is pretty much the other way around... can the camera sensor resolve the lens detail?

Digital cameras have always had anti-aliasing filters because they simply cannot resolve the finest detail from the lens. They suffer moire if the sampling is not AT LEAST double the detail level (Nyquist), which it has not been... so the cameras have required AA filters to blur away the finest detail too great to be resolved (to prevent the false aliasing detail called moire, due to insufficient sampling resolution).

The D810 has 36 megapixels (in a full frame sensor), judged just adequate resolution to dare leave off the anti-aliasing filter. But it is early yet, risky, moire will still be possible in some situations, so this would be considered absolute bare minimum sampling resolution. Far from any maximum for the lens. This bare minimum is not optimum, it is a bare minimum, and oversampling is always a better image. Preventing moire is simply a minumum requirement.

See http://www.scantips.com/lights/reslimit.html about Have We Reached a Resolution Limit?

Answer 3

By now, you've likely discovered that both lenses are capable of providing adequate image resolution on the D810. Only technique and execution are going to hold one back in this area.

One thing not mentioned by any other answer is how to test lens vs camera resolution without resorting to specialized tests or equipment (such as imatest).

Zeiss has an informal test called the "Fence Test" (see page 3 of this brochure). The basic premise is to take a photo of a subject that has features that can stress the limits of resolution by your sensor. A white-slatted fence in front of a darker background is an ideal subject, particularly at distance. Shooting this on digital, if you successfully get alternating colors of white/other on a pixel-by-pixel basis (at proper distance), then you are assured of being able to achieve maximum resolution provided by your camera with the given lens.

As mentioned in the citation, you can also test based on prior subjects or anything with alternating light/dark contrast. Here's an example of something I've shot and a corresponding crop that comes close to passing the Zeiss fence test.

Note the red box. Here's a 12x view of that area.

Note that I didn't get perfect pixel-by-pixel alternation in the feather detail of that Heron, but the slanted features look pretty good. Note that the main image has ~2.2 MP of resolution, and this 0.003 MP feature contributes little to overall image quality. Plus my application of sharpening is heavy-handed here, weakening the overall aesthetic quality of the image.

For portraits, perfect resolution is unlikely to contribute to great image quality as much as good tonality could. When shooting faces from a few feet away, the only things that are likely to resolve to near-pixel size detail are fine hairs and pores, neither of which are not going to be flattering, and can even get worse in the final image if you apply any sharpening to fit to resolution. Also, these features only get bigger when shooting at macro distance to get close-ups. You need much more depth of field at macro-distance to get enough detail, meaning these features will be more pronounced (at f/8 and smaller apertures). Conversely, your overall resolution will decrease as the D810's sensor will out-resolve any lens at f/9 or smaller, and some features may even exhibit softening from diffraction as soon as f/6.3 or f/7.1. If you have followed through on your photo-shoot, I'm sure you've noticed that close-up images of eyes and lips weren't very well resolved without resorting to much smaller apertures. You may even find that you couldn't get some images this close without specialized lighting.

If you aren't opposed to cropping an image from the D810, one way to cheat a little bit for resolution without resorting to advanced macro shooting techniques is to use wider lenses that focus pretty close but not quite at macro-like distance. You could use a 50mm macro lens, lenses like the Nikon 28mm f/2.8 AI-s (focuses to ~6", shoots almost an index-card (~4x6"/5x7.5") sized image at MFD), the Zeiss 35mm f/2 ZF/ZF.2/Milvus (focuses to ~9", shoots roughly a 7x10.5" image at MFD), etc. The wider the lens, and closer the close-focus distance, the better. You can also shoot at wider apertures and get the same DoF at double or even triple what you would expect at the ~100mm range. But again, as others have mentioned, one is not likely to get flattering images at distances this close, and you might still block your work lighting.

Answer 4

You need not worry; most lenses are up to the task. Some lenses are better than others, generally you get what you pay for.

Every lens is afflicted with defects that force substandard results. There are seven major defects that result in substandard performance.

1. Spherical Aberration
2. Coma Aberration
3. Astigmatism
4. Curvature of field
5. Distortion
6. Longitudinal Chromatic Aberration
7. Transverse Chromatic Aberration

The lens maker intermixes many different shaped lens elements, some with different densities. The idea is to mitigate however none are actually totally eliminated.

Additionally nature adds two more nemeses. These are diffraction and interference each can be devastating. Well studied by John William Strutt English physicist 1842 – 1919 titled 3rd Baron Rayleigh Nobel Prize Laureate. As Astronomer Royal he published what we call the Rayleigh Criterion.

Still valid today with all our ability to make lenses.

The resolving power of a lens is the lines resolved per millimeter. We are taking about the ability to perceive that you looking at lines that are close and you can identify that a space exits between the lines. This ability is a combination of aberration mitigation and the working diameter of a lens. The working diameter divided into the focal length is the focal ratio.

The formula for the Rayleigh Criterion is 1392 / f-number. (Remains valid as the best we can do to date.

Thus f/1 = 1392 lines per millimeter resolved f/1.4 = 994 lpm f/2 = 696 lpm f/2.8 = 497 lpm f/4 = 348 lpm f/5.6 = 249 lpm f/8 = 174 lpm f/11 = 127 lpm f/16 = 87 lpm f/22 = 63 lpm

The larger openings are generally too injured by aberrations so we stop down to gain acuity. The resolving power of a lens at f/8 is higher than pictorially useful. As we stop down, diffraction and interference induce substandard acuity.

Answer 5

You don't need more resolution just because you're shooting close. You need it if you intend to make enormous prints.

Once you're over perhaps 8MP, pixel counts don't have much to do with resolution anyway.