Charles 46277 Loc: Fulton County, KY

The photo attached was taken with Hasselblad H2, normal 80mm f2.8 lens with 2-inch macro extension tube, handheld with photoflood on the right and on-camera fill flash, 1/800 second at f32.
Yes, f32.
I see this photo of a streptocarpus sprig is not high art, but when I look at it from 3 feet on my monitor, it is a nice picture. I did not cook it much in PS, just a bit of crop and spotting--it may look sharpened, but it wasn't. If you open the Download picture you will see it better. My reason to post it is to discuss small apertures, particularly in macro shots. With the typical wide-open aperture, or close to it, the picture is impossible--the main attraction is a big blurry thing with a few remarkably sharp hairs on one of the leaves.
Why 3 feet? Well, facts are facts--though f32 improves the overall depth of field tremendously, when you get close to it you see that the finest hairs are not so sharp. (Still, in the plane of focus they are quite sharp, around 3 o'clock in the image... When parts of a picture are razor-sharp, the impression is sharpness.)
My personal take is that aperture is not dictated by one rule, but adjustable to our purpose or effect. If you want the whole sprig in focus, a small aperture is necessary. (Yes, you can back up and use wider aperture and/or wider lens--but then you have to blow it up in processing and lose what you gained by backing up or using wider lens and/or aperture--the sharpness is lost later. Magnification is the inherent threat, whether when shooting or processing.)
If I wanted to make a big enlargement, my first plan would be to hang it on a wall where people must stand back, such as on the wall behind the breakfast bar or with big furniture in front of it. This is not resorting to desperate means, but merely taking the whole world into account when we say what is right or wrong in photography. (I would not be tempted to fuzz it up with special effects unless it is for a greeting card. Or should I?)
A medium format camera can get away with (or demand) smaller apertures--f22 was a starting place with 4x5, but for macro work the problems with very small apertures are not much improved by larger format. Or are they? I know that for general photography, I use a smaller aperture with the Hasselblad than the Canon 650 (APS). The f2.8 lens used here is quite fast for medium format.

(Download)

photosbytw Loc: Blue Ridge Mountains

My first response was to ask if there was any wind? (As it is the vile and evil nemesis of any macro photographer), but(imho) f/32 equals diffraction. Also, your using about 50mm of extension tube(s) and your working distance is 3'? The photoflood wouldn't be of much use(except maybe to view your subject when composing) and I'm not sure about using the on camera flash............try using using an off camera flash as you have more control as to the placement of the flash and its power settings.

CHG_CANON Loc: the Windy City

You should look at the image at 100% with a more critical eye. There's a amazing amount of sensor dust all over the entire frame, even what looks like a hair near the steam at the bottom of the frame.

Regarding small apertures and 'sharpness', none of the fine 'hairs' are well defined. The sharpest portion of the image does not extend over the entirety of one leaf. A focus stack of images with a wider (and more reasonable) aperture could yield a merged image with more detailed 'sharpness' covering the tip of the nearest leaf through the far side (from the camera) of the top four leaves of the plant. Granted, that's a lot more work and depends on both tripod and expert computer equipment and software, but this is how these amazingly sharp macro images are being produced with digital cameras in 2019.

Do you have any comparative images at say f/11 to f/13? For the same details / point of focus within the image, are the hair details sharper for apertures less prone to diffraction? Is the depth of field unacceptable in these other versions or more pleasing?

Longshadow Loc: Audubon, PA, United States

I'd just print it and not worry about people with magnifying glasses.
(I myself wouldn't look for each hair being crisp.)

Optimal viewing distance for an 8x12 would be about 2 feet, a 24x36 would be about 5-1/2 feet.
(Based on 1.5 x the hypotenuse of the print.)

Charles 46277 Loc: Fulton County, KY

There was no wind in the living room. I do not recall the shooting distance (3 feet was my viewing distance of the photo on the computer monitor as I tried looking at if from various distances).

And yes--of course there is diffraction, but also greater depth of field, as shown--that is the discussion point. Off-camera flash is a nuisance here, for me anyway--I had no particular modeling of light in mind for it, as one would have with a person. A sense of depth comes from the way the leaves show variations of shadow in various areas. The plant is also in front of a window for backlight.

Charles 46277 Loc: Fulton County, KY

Thanks, Longshadow. Why do you say viewing distance is ideally 1.5 times the hypoteneuse of the image? Is that a famous rule? I once read that it was the focal length of the lens times degree of enlargement of the photo (such as 12-inch lens times 1 when the 12-inch negative is contact-printed, so viewed at 12 inches... no idea why).
Surely the optimal viewing distance must take into account the angle of view of the lens (focal length)? I notice that if I back up to look at a telephoto shot, the compressed effect goes away, or if I get close to a wide-angle shot, the so-called "wide-angle distortion" goes away... I discovered this from an article by one of the Deardorf brothers, long ago. (I think his name was Merle. Memory is the second thing to go--I forget the first.)

Charles 46277 Loc: Fulton County, KY

Charles 46277 Loc: Fulton County, KY

Yes, CHG, I did notice when studying it that the sensor needs cleaning. I bought the camera used recently, Is cleaning the sensor something I should do myself? It is a Phase One P-30 back, so if I take it off it is readily accessed. I hope the surface does not have to be removed to clean it under the glass...

Larger apertures were not good images of the sprig, though the improvement was gradual.

CHG_CANON Loc: the Windy City

I clean my sensor myself, with VisibleDust Swabs. I bought a whole bunch in the past, but I'm unsure if this specific product is still available. When I first received my Sony a7II used, it was worse than even this example, but cleaned up nice with a 'wet cleaning'.

photosbytw Loc: Blue Ridge Mountains

[quote=Charles 46277]There was no wind in the living room. I do not recall the shooting distance (3 feet was my viewing distance of the photo on the computer monitor as I tried looking at if from various distances).

Yikes, my bad on the WD(I'm not much of a speed reader anymore) As for the living room, well............
As for using a high aperture...........if depth of field is an issue then focus stack. It's only an opinion but you might want to rethink the off camera flash...........nuisance versus an image you can brag about...........

Bill P

We all refer to dust as on the sensor, but that's not true. It's on the cover glass, part of the disturbingly thick layer of stuff over the sensor, so if it's under the stack of glass then you are in real trouble. Cleaning the cover glass is not that hard ona camera without IBIS. But you must ask yourself, am I mechanically inclined? Do I have decent eye hand coordination? Am I able to do other precision tasks, or are you what we used to call ham handed? If not, it isn't hard. there are a proliferation of websites with instructions. All you will need are some simple tools, sensor swabs and a bottle of cleaner that will cost mere pocket change compared to what you paid for the camera.

Longshadow Loc: Audubon, PA, United States

I've always gone by the 1.5 x the diagonal (hypotenuse) rule, as it also applies to other artwork (paintings, pencil sketches, etc.) that do not have a lens associated with them. Working with one basic rule is much simpler than figuring what type of artwork I have to figure the best viewing distance. Why make things more complicated than they need be? Why worry about any lens compression or expansion? It is an image that one is viewing. I've never considered nor incorporated a lens value into the viewing distance of any artwork. As for the telephoto/wide angle phenomena, it may have an effect, but I've never concerned myself with it. Don't forget the mind also analyses and adjusts for what the eye sees, ...perception.

The the "optimum" viewing distance is relative. Haven't you gotten closer or farther away to view artwork? The optimum is based on the distance at which MOST people can comfortably focus on the entire image as opposed to just a piece of it (too close).

Now watch someone add something about pixel density to complicate things even more....

User ID

80mm lens at f/32 has same size aperture
as 40mm lens at f/16. Not severely small
so not a major diffraction situation.

Whatever sharpness may be lacking here
cannot be entirely blamed on diffraction.
Diffraction may be having some effect but
is less than half the problem.

Charles 46277 Loc: Fulton County, KY

CHG, I see kits for this online--a video looks like you just clean the glass over the sensor, right? You do not have to go under that to the sensor itself? It looks like the glass has many tiny inset screws attaching it.
Once cleaned and attached to the camera body, it should stay clean, yes? Well, eventually when the mirror flips up through use it might get dust again by way of lens changing.

CHG_CANON Loc: the Windy City

Yes, you just 'wipe' the glass that you 'see' as the sensor. How clean is stays depends on your equipment and the environment where you change your lenses. This link is I demo I did with just a Giotto Rocket-air: An exercise in sensor cleaning . After you've done a wet cleaning and the sensor is 'clean' as confirmed with your test images, a Rocket-Air becomes your first cleaning tool if / when you see any new dust, particularly for cameras that don't have a self-clean / shake cycle.