[stemked]

Hi all.

I think I have this clear but I'd like to check with you first.

I do a lot of macro nature photography. Some of the 'larger' animals I do macro work on include amphibians, especially salamanders, which can actually be rather large subjects (maybe up to ~5 inches or ~12 cm). I currently normally use a 100mm DAW f2.8, but even stopping the lens down to f11 or f16 I do not necessarily get everything in focus. Would I get more of the animal in focus if I were to use a 1:1 50mm macro (or for that matter 35mm macro) using similar f stops than my current macro lenses? I would imaging I do, but the lack of a water resistant 50mm macro might be the reason I stick to the 100mm (these are amphibians I'm shooting after all).

Just wondering

[othar]

No I don't think you do, just the perspective would change a little.
You wouldn't get more in focus with the same aperture because you would also have to go nearer to reach the same magnification.

The only options you have, in my opinion: use a smaller aperture or do focus stacking

[GUB]

In photography that is not macro
For a given format
for a given aperture
for a given subject/image magnification
All focal lengths will have the same depth of field.
This rule bends as you approach macro.

[Bob 256]

A 50mm lens at f8 will give better depth of field than a 100mm at that same f stop but you'll also have a smaller image. If you enlarge that image to the same size as would have been produced by the 100mm lens, it will exhibit the same depth of field, but you'll be at a disadvantage because of the enlarging and the fewer pixels involved in the cropped/enlarged image. The 100mm also has the advantage you mentioned - you get more subject to lens distance (and a somewhat different subject perspective that's not so much like using a wide angle lens up close to a subject). Keep in mind that the f-stop you are using may be higher than the labeled f-stop since the focal length of the lens is extended at macro distances so f16 can become f32 at 1:1.


The only other approach to getting better DOF (other than using smaller f-stops which has its own disadvantages in terms of IQ) is to do focus slicing where the lens is refocused a number of times at different "slices" and then those can be recombined using software but that approach is not feasible for subjects that move since the exposures are taken over time.

Flash (probably using a ring light) can allow higher f-stops and better DOF and you have to weigh the tradeoff between the reduced IQ with the improvement in DOF.

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Last edited by Bob 256; 11-16-2020 at 12:12 PM.

[othar]

A 50mm lens at f8 will give better depth of field than a 100mm at that same f stop but you'll also have a smaller image. If you enlarge that image to the same size as would have been produced by the 100mm lens, it will exhibit the same depth of field, but you'll be at a disadvantage because of the enlarging and the fewer pixels involved in the cropped/enlarged image.

While I come to the same conclusion that DOF will not improve by using a smaller focal length, I disagree with the quoted declaration of you. The image of a 50mm lens at 1:1 magnification will not be smaller than with the 100mm lens at 1:1 magnification, you will just have to move closer to your subject to reach that magnification

[dms]

As mentioned the perspective (relative size of nearer-to-farther away) changes, but the DOF is only a function of f-stop and magnifcation. There is a benefit of having more or less working distance (flowers and books: lesser FL is often better; skittish insects: longer FL usually), but whatever distance is required to get the desired magnification, will yield the same DOF.

[stevebrot]

100mm macro (1:1) vs 50mm macro (1:1) Depth of view question

As noted above, DOF remains the same but with reduced working distance with the 50mm.

Below is my Sigma 50/2.8 EX DG Macro at 1:1...




Steve

[Bob 256]

While I come to the same conclusion that DOF will not improve by using a smaller focal length, I disagree with the quoted declaration of you. The image of a 50mm lens at 1:1 magnification will not be smaller than with the 100mm lens at 1:1 magnification, you will just have to move closer to your subject to reach that magnification

Sorry, I wasn't clear about that - I was referring to use at the listed (infinity) focal length. As I mentioned, when used for macro work, the actual focal length with increase beyond the listed focal length. dms said it correctly in post #6.

[mikeprotts]

Hi all.

I think I have this clear but I'd like to check with you first.

I do a lot of macro nature photography. Some of the 'larger' animals I do macro work on include amphibians, especially salamanders, which can actually be rather large subjects (maybe up to ~5 inches or ~12 cm). I currently normally use a 100mm DAW f2.8, but even stopping the lens down to f11 or f16 I do not necessarily get everything in focus. Would I get more of the animal in focus if I were to use a 1:1 50mm macro (or for that matter 35mm macro) using similar f stops than my current macro lenses? I would imaging I do, but the lack of a water resistant 50mm macro might be the reason I stick to the 100mm (these are amphibians I'm shooting after all).

Just wondering

It may be that you need to accept a smaller (cropped) image and use the wider lens at a little distance or the 100mm at a couple of yards.

This DOF calculator has a very helpful visual guide.
Depth of Field (DoF) calculator | PhotoPills

[Bob 256]

It may be that you need to accept a smaller (cropped) image and use the wider lens at a little distance or the 100mm at a couple of yards.

This DOF calculator has a very helpful visual guide.
Depth of Field (DoF) calculator | PhotoPills

And here's another specifically for macro lenses:

Lens Magnification and Depth of Field Calculator

You can try your two lenses: 100mm/subject distance 200mm and 50mm/subject distance 100mm which yield 1:1 magnifications

Also check out the "Accuracy" tab at that site which has some good explanations of DOF in macro cases.

[stevebrot]

Sorry, I wasn't clear about that - I was referring to use at the listed (infinity) focal length. As I mentioned, when used for macro work, the actual focal length with increase beyond the listed focal length. dms said it correctly in post #6.

Your comment in post #4 was perfectly clear and made no reference indicating that it was off-topic (meaning infinity rather than at 1:1). As for relative aperture (f-number), it is the absolute aperture* that, along with magnification (1:1 in this case), that determines DOF. That is why focal length, effective or otherwise, is irrelevant to DOF.

http://coinimaging.com/dof_macro.html (probably the best explanation I know of without a lot of math)


Steve

* More correctly, entrance pupil size

[stemked]

Thanks folks!

[DWS1]

From the limited macro work I've done, I don't think the DOF will change much/

[peggers]

As noted above, DOF remains the same but with reduced working distance with the 50mm.

Below is my Sigma 50/2.8 EX DG Macro at 1:1...




Steve

Goodness me, that is close! I have an old Takumar 50mm f4, but it doesn't get anywhere near that close.

[stevebrot]

Goodness me, that is close! I have an old Takumar 50mm f4, but it doesn't get anywhere near that close.

The working distance from one lens to another varies somewhat depending on whether there are floating elements and how deep the front element is placed. If magnification is based on extension alone, 1:1 is attained with an extension equivalent to the lens focal length with working distance being 2x the nominal focal length (50mm) minus the lens body length at full extension.*

The lens in the photo has a floating element and working distance suffers a bit as a result. It would also help if I removed the hood.


Steve

* More directly, minimum focus distance (measured to focal plane) minus lens flange distance (45.6mm) minus lens length at full extension.