Technique for high-res iris macro (focus stacking + lighting) — references attached

[AlicjaAnastazja]

Hi,
I graduated from the Academy of Fine Arts in Warsaw (degree in photography). I’m currently working on macro photography of the iris and my goal is the highest possible quality with a three-dimensional look.
I’ve attached reference images, a few full frames and crops, and (where available) stack slices.
My questions:

• What lighting setup delivers the most three-dimensional appearance at this scale?
• Would you recommend a macro lens, microscope objective, or a bellows + objective approach, and what magnification range?
• For focus stacking: suggested frames count and step size? Recommended stacking software?

***

The reference images I attached were found on Pinterest. Unfortunately, the author/photographer was not credited there, so I don’t know the original source.

Thanks in advance for practical tips — I’d appreciate concrete step-by-step advice.
Best

Alicja

 

[Lester Lefkowitz]

Sounds like you are looking for a "formula" for a specific type of macro photography. Photographing an eyeball is a challenge unto ityself, but as far as how to achieve magnification, there are numerous possibiities.

Because the cornea is hemispherical, it is tricky to light it without annoying reflections from the light source. For best three-dimensionality, have the light come in from the side. Invariably you will probably get at least one hot spot, that will have to be removed in post production. I have found a small light source, rather than a broad one, is best (see photo below).

I doubt very much that you will be able to use photo stacking. If you use flash (as you should), as soon as the flash goes off the person will blink and the iris will immediately close down. If you use continuous light, which must be bright enough for moderately fast shutter speeds, the pupils will get very small.

As to magnification and lens, it depends on the camera format (full-frame, APS-C, Micro4/3) and how close you want to get. The typical hunman eye is about 25mm in diameter, so if you want the entire eyeball, any 1X macro lens will do. If you want to get higher magnification, there are numerous methods: Laowa 2X macro lenses; Laowa 2.5-5X macro lens, extension tubes added to 1X macro lenses; reversed enlarger lenses on tubes or bellows. Use as long a focal length as possible to get maximum working distance.

You will need some type of setup to keep the subject's head steady. Ambient light in the room will determine the size of the pupil. I recommend using a good focusing slide so you can quickly adjust focus (do not use autofocus). Since you can't use focus stacking, use small apertures - f/11, f/16 - depth-of--field will be more important than diffraction softening, which can easily be sharpened in many of the great post ptoduction programs (like Topaz).

You asked abiout the possble use of microscope objectives, which one thinks about starting at around 5X (assuming you just want to photograph a small section of the iris). But they have a fixed, very large aperture, which mean very shallow DOF, I think inasppropriate for the very 3D structure of an iris.

If you've never done macro photography before, I suggest to first practice on something simple, like flowers. Maro photography is NOT the same as conventional photography

Suggestion: Prtactice on some cheap glass eyeball props found on Amazon. Human subjects will not be happy sitting for a long time while you figure out how to do this.

Lester Lefkowitz, author of The Manual of Close-Up and Macro Photography, Volumes I & II

www.MacroPhotographer.net

 

[c h u n k]

I just spent some time looking for a photographer I read about a few months ago, who was working on a "iris photography" project. Sadly, I couldnt find them again. I will try to look more, but what I do remember is he/she (cant remember if was male or female so Ill have to take some liberties referencing) was photographing the eye at an angle instead of directly, along with lighting from an angle and the photos were pretty incredible, given that Ive seen a zillion photographs of the eyeball. Everyone who has ventured into macro has photographed eyeballs - but seldom are they impressive at all. The angle and lighting gave significantly more depth to the photo. It seemed like you could fall in to the pupil, or climb around on the threads that make the iris. Ive actually been meaning to attempt this sometime myself. If I do soon, I will share to this thread.

I do agree that focus stacking would be very tricky due to the pupil restricting with light. But wheneber someone suggests something isnt possible in photography, I dont let it stop me from trying or contintinuing to search for someone that has already done it succesfully. I think it is probably possible because 1) the iris is relatively large, so you wont need many exposures, 2) lowlight capabilities with cameras has come a long way and using fullframe sensor is definitely fine for such a large subject 3) you can use constant light and diffuse it. I dont think you want pinned pupils from excessive light, but you also dont want fully dialated pupils either.

But, once again, this is a relatively large aubject and because if this, we wont hit diffraction limits as fast as we do with smaller subjects that need higher magnification, so you can also juat try to stop down more than you normally would to eek out a little more DOF.

I really would try to do something different, or at least a step above the run of the mill eyeball photos everyone has experimented with. As I mentioned above, based on what I saw from that other photographer, its definitely possible.

Share your results.

 

[c h u n k]

I spent some time looking and Im fairly confident stacks are possible. Some people are using small constant led lights positioned to the side, not directly, of the eye. If you get the subject to anchor his or her head to something so they dont move while fixing their view on an object, Im sure it can be done

 

[ThrillaMozilla]

You didn't say what your purpose was, or your requirements, or your budget, or what equipment you might have already. Unless you can find a lot of information from someone who has done it, you might improve the responses by giving us that information.

I can give you some general guidance, however.

I guess the iris is about 1 cm in diameter. For small format cameras -- Micro 4/3, APS-C, or full frame (FF) -- the picture height is 18 mm, 24 mm, or 36 mm respectively. Thus, you need magnification of roughly 2 to fill most of the frame. A little less for MFT, and a little more for FF. You could use a 1:1 macro lens to fill the frame partly, but 2:1 would be better.

I would not recommend a conventional microscope lens. A 1x objective or 2x objective is a specialized, very expensive lens. They are designed for quite close focusing. You could use a 5x or 10x objective at greater distance, but they are not optimized for that use. You could use a reversed enlarging lens, which would be optimized for about 3:1 or 10:1. I don't see any reason to use either unless you just happen to have the equipment. You would need a bellows or some kind of focusing unit, and you would lose the necessary convenience of auto aperture control.

A macro lens is optimized for your purpose. You could also use other camera lenses with extension tubes or a close-up attachment lens. The macro lens is better. If I were doing it, I would first try my Canon EF-S 60 mm macro lens with an APS-C camera, because that's the lens I have for it. I would probably try it with extension tubes.

The depth of field and diffraction are both determined by exactly the same parameters, so you cannot optimize both, and you may have to compromise. If you want more information on DoF, this post explains the principle. Line TU is the aperture diameter, and at macro distances, angle TPU determines both DoF and diffraction. To increase DoF you can narrow the aperture or increase the distance.

A single exposure is preferable to a focus stack, as long as it gives you a suitable combination of depth of field and diffraction. Focus stacking could extend the depth of field, but the head and eye must be absolutely stationary for this to work. Some Olympus, OM-Sytems, Canon, and Sony cameras have automatic focus bracketing, which would give you a suitable set of bracketed exposures. I'm not sure about Nikon.

Lighting? Darned if I know. I would say oblique (i.e., darkfield) lighting is what you need. Ringlights? Darned if I know. You must avoid reflections from the cornea. It doesn't necessarily have to be flash, although that would stop motion.