carney2 wrote:
Due to being stuck in one place because of the virus and the advancing years, I have begun to shoot some macro. (Why it is called macro and not micro has always bothered me.) I 've seen some really good macro photos, and some have been "focus stacked." I don't focus stack, considering it too much fuss and bother. Or, as one long time photographer friend of mine once said, "I didn't get into this hobby to play with computers." Rather, I have a macro lens that will get me to f/32, so I go for maximum depth of field and add needed light via a flash or a reflector.
Opinions?
Due to being stuck in one place because of the vir... (
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The main concern using very small apertures is "diffraction". That's an optical effect the causes loss of fine detail.
With a camera around 20MP and assuming a print size around 8x10 (or 8x12) without cropping, diffraction begins occurring about f/7.1 with APS-C cameras or f/10 with full frame. As the lens is stopped down, or with higher resolution cameras or cameras that use smaller format sensors, and with greater enlargement of the image diffraction gradually increases. In truth, diffraction can be dealt with up to around f/16 pretty easily simply by doing a bit more sharpening in post-processing. Maybe even f/22. But caution should be used beyond that (hence, people use larger apertures that render less depth of field, but take multiple image and do "focus stacking").
There's also diffraction-related concern about the "effective aperture" of a lens. Macro lenses that extend, that grow longer as they are focused closer, will also see their effective aperture size reduced. An extreme example of this is a Canon MP-E 65mm Macro lens I use. This is an ultra-high magnification lens. In fact, the
least magnification it can do is 1:1 that's the max magnification many other macro lenses can do. In other words, this lens is "macro only" (or "micro" if using Nikon lenses... or "mikro" if shooting with some European brands). And the MP-E 65mm goes as high as 5:1 or 5X magnification. That can fill a camera's viewfinder with a grain of uncooked rice.
But then there is this lens' aperture, which is also extreme, because it nearly doubles in length when focused to it's maximum. At minimum focus distance, it's f/2.8 wide open and the smallest aperture you can stop it down to is f/16. But, when focused to maximum magnification where the lens is extended to it's longest, that same f/16 setting becomes an
effective f/96 aperture as far as exposure is concerned. I don't know that this affects depth of field, as it's extremely shallow regardless. I also am not certain if the effective aperture also affects diffraction.... but from what I can tell looking at images, I think it does.
Below was shot with the MP-E 65mm at around 3.5X magnification and set to f/16... At these settings, the depth of field is a little less than 1/2 a millimeter and the effective aperture is approx. f/70. To me there appears to be quite a bit of detail lost to diffraction:
Would the above have been better using a larger aperture and focus stacked? Yes, but it also would have been impossible. Even a tiny, newly hatched snail is too fast moving to be able to focus stack! (It was difficult even getting focused on the subject at 3.5X... the MP-E 65mm is manual focus only).
Shooting macro is always sort of a "balancing act"... First you need to decide a focal length. Too short reduces working distance, putting you right on top of the subject. Too long makes for very shallow depth of field and difficulty getting a steady shot. You also have to weigh aperture/shutter speed/ISO versus depth of field and stability. How small aperture is too small? How high ISO is too high? How slow shutter speed is too slow?
One thing that can help is flash. There are macro specific flashes, but a lot can be done with a standard flash.
The snail above what shot with a ring light. I only use that with very high magnification... 2:1 (2X) and higher. I'm not a fan of ring lights at lower magnifications. They look "clinical" to me, with too flat lighting. For that reason, the MP-E 65mm is the only macro lens I use with a ring light.
For other macro lenses with less magnification, I use a twin light. That's a flash with two separate, small heads. I use them on a dual flash bracket so they can be adjusted a variety of ways to provide main and fill light from various angles.
But it is also possible to use standard flashes for macro work. All you have to do is diffuse them to reduce their output, so they won't overpower the close-up subject. I use several layers of gauze bandage held over the flash head with a rubber band. The other trick is positioning the flash off-camera. I usually just hold it where I want it. I've used this often in the field, when I didn't have a macro flash with me. I've used it with a variety of macro lenses up to 1:1 or a bit more magnification, and with non-macro lenses being made to focus closer with extension tubes (such as the spider below, which was shot with a 70-200mm zoom w/25mm extension... all the other images were shot with 100mm macro lens):
The praying mantis image above illustrates something else macro flash can do... There was a tangle of grasses, leaves and stems behind the subject, making it difficult to distinguish. By setting up the camera to significantly underexpose the background and the flash to illuminate the closer subject, much of that background disappears. You can control just how much background appears by balancing the flash against ambient light. The spider and the turtle used lower power fill flash, that allows much more of the background to be recorded in the image. In the image of the spider, the background was quite distant and shaded, so it was naturally dark. That's different from the praying mantis, where the dark background was created in the camera.
The pink amaryllis further above was actually a black felt background behind the flower, to hide a gray wall that was too close to effectively blur down or make go dark any other way. In that case, the twin light flash was used for very soft and slight fill, too, which wouldn't have darkened the background.
Overall, however you do it, flash can be extremely useful for macro work. If you have already done so, I suggest you experiment with using it.
I have not seriously tackled focus stacking yet, either. But I know it may be the only way to get acceptable shots, in some cases, and I plan to do more of it in the future.
Have fun experimenting!