macro lens design and focus stacking artifacts

[Pd printer]

I am using a process lens on bellows and there are 3 different ways to do focus bracketing:

A: focus with the front standard, the lens distance to subject and to sensor changes

B: focus witch the back standard: distance to subject stays constant distance to sensor changes

C: focus with a rail: distance to subject changes, distance to sensor stays constant.

Changes of the distance lens to subject causes a change in perspective and changes of distance lens to sensor causes change in image size (focus breathing/ change in viewing angle)

I find more or less no stacking artifacts if I am using method B but with the other 2 methods. Apparently the focus stacking software (both Zerene and Helicon) are compensating well for focus breathing but not for change in perspective.

Almost all modern macro lenses have internal focusing (to facilitate AF) and if one uses the internal focus bracketing mode the front lens stays fixed so the distance to subject is also fixed. So I wonder if various modern macro lenses have less artifacts when using the internal focus instead of focusing by changing the distance to subject (either by rail or handheld gliding method).

I could see some variables to these answers: magnification and lens design (entrance pupil constant or not) so it would interesting to see if that is the case with different recent macro lenses.

 

[macrophoto_markus]

I am using a process lens on bellows and there are 3 different ways to do focus bracketing:

A: focus with the front standard, the lens distance to subject and to sensor changes

B: focus witch the back standard: distance to subject stays constant distance to sensor changes

C: focus with a rail: distance to subject changes, distance to sensor stays constant.

Changes of the distance lens to subject causes a change in perspective and changes of distance lens to sensor causes change in image size (focus breathing/ change in viewing angle)

I find more or less no stacking artifacts if I am using method B but with the other 2 methods. Apparently the focus stacking software (both Zerene and Helicon) are compensating well for focus breathing but not for change in perspective.

Almost all modern macro lenses have internal focusing (to facilitate AF) and if one uses the internal focus bracketing mode the front lens stays fixed so the distance to subject is also fixed. So I wonder if various modern macro lenses have less artifacts when using the internal focus instead of focusing by changing the distance to subject (either by rail or handheld gliding method).

I could see some variables to these answers: magnification and lens design (entrance pupil constant or not) so it would interesting to see if that is the case with different recent macro lenses.

You will still get stacking artifacts (ghosting/focus breathing) with the new high end macro lenses, but the results are very good, and you can fix most of the artifacts easily in photoshop. Stacking with focus bracketing works well even at very high magnifications with teleconverts attached on the OM 90mm, but you'll have to clean up very deep stacks.


Here's an example of the 90mm + MC20 at 4x magnification, some slime mold, had to be cleaned up quite a bit but not very difficult.


Here is an example with the MC14 attached at 2.8x, not a lot of issues, just retouching the bristles as they get lost in deep stacks. Handheld, 181 frames


Here's an opposite example at a very low magnification with less images and an easier subject. Handheld

 

[Pd printer]

I am using a process lens on bellows and there are 3 different ways to do focus bracketing:

A: focus with the front standard, the lens distance to subject and to sensor changes

B: focus witch the back standard: distance to subject stays constant distance to sensor changes

C: focus with a rail: distance to subject changes, distance to sensor stays constant.

Changes of the distance lens to subject causes a change in perspective and changes of distance lens to sensor causes change in image size (focus breathing/ change in viewing angle)

I find more or less no stacking artifacts if I am using method B but with the other 2 methods. Apparently the focus stacking software (both Zerene and Helicon) are compensating well for focus breathing but not for change in perspective.

Almost all modern macro lenses have internal focusing (to facilitate AF) and if one uses the internal focus bracketing mode the front lens stays fixed so the distance to subject is also fixed. So I wonder if various modern macro lenses have less artifacts when using the internal focus instead of focusing by changing the distance to subject (either by rail or handheld gliding method).

I could see some variables to these answers: magnification and lens design (entrance pupil constant or not) so it would interesting to see if that is the case with different recent macro lenses.

You will still get stacking artifacts (ghosting/focus breathing) with the new high end macro lenses, but the results are very good, and you can fix most of the artifacts easily in photoshop. Stacking with focus bracketing works well even at very high magnifications with teleconverts attached on the OM 90mm, but you'll have to clean up very deep stacks.


Here's an example of the 90mm + MC20 at 4x magnification, some slime mold, had to be cleaned up quite a bit but not very difficult.


Here is an example with the MC14 attached at 2.8x, not a lot of issues, just retouching the bristles as they get lost in deep stacks. Handheld, 181 frames


Here's an opposite example at a very low magnification with less images and an easier subject. Handheld

all of them look very good, which method did you use focus bracketing in camera or gliding?

 

[macrophoto_markus]

I am using a process lens on bellows and there are 3 different ways to do focus bracketing:

A: focus with the front standard, the lens distance to subject and to sensor changes

B: focus witch the back standard: distance to subject stays constant distance to sensor changes

C: focus with a rail: distance to subject changes, distance to sensor stays constant.

Changes of the distance lens to subject causes a change in perspective and changes of distance lens to sensor causes change in image size (focus breathing/ change in viewing angle)

I find more or less no stacking artifacts if I am using method B but with the other 2 methods. Apparently the focus stacking software (both Zerene and Helicon) are compensating well for focus breathing but not for change in perspective.

Almost all modern macro lenses have internal focusing (to facilitate AF) and if one uses the internal focus bracketing mode the front lens stays fixed so the distance to subject is also fixed. So I wonder if various modern macro lenses have less artifacts when using the internal focus instead of focusing by changing the distance to subject (either by rail or handheld gliding method).

I could see some variables to these answers: magnification and lens design (entrance pupil constant or not) so it would interesting to see if that is the case with different recent macro lenses.

You will still get stacking artifacts (ghosting/focus breathing) with the new high end macro lenses, but the results are very good, and you can fix most of the artifacts easily in photoshop. Stacking with focus bracketing works well even at very high magnifications with teleconverts attached on the OM 90mm, but you'll have to clean up very deep stacks.


Here's an example of the 90mm + MC20 at 4x magnification, some slime mold, had to be cleaned up quite a bit but not very difficult.


Here is an example with the MC14 attached at 2.8x, not a lot of issues, just retouching the bristles as they get lost in deep stacks. Handheld, 181 frames


Here's an opposite example at a very low magnification with less images and an easier subject. Handheld

all of them look very good, which method did you use focus bracketing in camera or gliding?

Thanks, Focus bracketing in camera.

 

[Lester Lefkowitz]

There’s theory and then there’s practicality.

It is hard to avoid stacking artifacts all together because you are dealing with the fact that images at the far end of the stack are shot through out-of-focus blurs from the foreground. When artifacts occur, always try the various algorithms in both Helicon (A, B and C) and Zerene (DMap and Pmax); there is usually one better than another. But for critical work, and zoomed into 100%, invariably some post-production retouching will be required...more or less.

When a focusing rail is used, the magnification remains constant but the perspective changes because the geometrical relationship between subject and camera changes. However, at high magnification that change is miniscule, but in the close-up range, especially when a subject is shot at an angle, the effect is more pronounced. Each slice shows the subject in a slightly different position, as though there was motion during the sequence, and that’s not so easy for Helicon or Zerene to overcome completely.

Turing the focusing ring keeps the camera-to-subject perspective constant, but now the magnification is changing between slices. Helicon and Zerene seem to handle this a bit better.

Moving the rear standard on a bellows is ideal at any magnification, since perspective remains constant, as does the position of the entrance pupil. However, this is not very practical because there is no practical way to precisely move the rear bellows standard in a repeatable way unless you have a very light touch of the positioning knob. Also, the only company today that makes a bellows with an adjustable rear standard is Noflex, and with the necessary camera and lens adapters, price is close to $900. An alternative on the used marker are the beautiful Nikon PB-4 and PB-6 bellows.

Note than at high magnification the step size by moving the rear standard can be larger that what is required for moving either the front standard or a focusing rail, since the depth-of focus is greater that the depth-of-field, and that relationship grows with magnification.

Moving the front standard on a bellows is like moving the focusing ring on a lens; magnification changes slightly, but is inconsequential for small subjects and is easily handled by stacking software.

Practically: Handholding in the field, there is the gliding-into-focus technique, or auto-focus bracketing if practical on your camera. As noted above, the autofocus bracketing might provide fewer stacking artifacts. On a tripod, again, autofocus bracketing or manually turning the focusing ring (if you have a lens with a nice long focus throw and have a deft touch). The gliding-into-focus technique can be used above 1X, whereas the other possibilities are limited to 1X (or maybe somewhat above when using a teleconverter or automatic extension tube).

For tripod work above 1X, a focusing slide is really the only practical solution.

For what it’s worth, modern macro lenses (the 1X autofocus variety) achieve magnification not by lens extension as in the old days, but by changing (shortening) the effective focal length of the optics. Technically, this changes the magnification a bit, but it’s inconsequential for our purposes. But what is consequential, is that for many lenses, the change in focal length can be as much as 25-30% less, with attendant effect of working distance; your 105mm macro lens maybe more like 80mm at 1X.

Here’s something to consider. Stacking artifacts become more prevalent as depth-of-field decreases. If you close the lens down by two stops, D-O-F doubles, which noticeably decreases artifacts, and cuts the number of required steps sizes in half. I know, diffraction, diffraction, diffraction , but modern post-production sharpening algorithms are quite remarkable, so it’s something to consider. Everything is a trade-off. And then there’s Photoshop.

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

www.MacroPhotographer.net

 

[jim mij]

thats an interesting trio, it would be good to see a before and after of pic 2 if you still have the original to see where you tweaked things.

That said I do find while stacks have a similar style of problem each stack has that in different areas of the frame

 

[Pd printer]

There’s theory and then there’s practicality.

It is hard to avoid stacking artifacts all together because you are dealing with the fact that images at the far end of the stack are shot through out-of-focus blurs from the foreground. When artifacts occur, always try the various algorithms in both Helicon (A, B and C) and Zerene (DMap and Pmax); there is usually one better than another. But for critical work, and zoomed into 100%, invariably some post-production retouching will be required...more or less.

When a focusing rail is used, the magnification remains constant but the perspective changes because the geometrical relationship between subject and camera changes. However, at high magnification that change is miniscule, but in the close-up range, especially when a subject is shot at an angle, the effect is more pronounced. Each slice shows the subject in a slightly different position, as though there was motion during the sequence, and that’s not so easy for Helicon or Zerene to overcome completely.

Turing the focusing ring keeps the camera-to-subject perspective constant, but now the magnification is changing between slices. Helicon and Zerene seem to handle this a bit better.

Moving the rear standard on a bellows is ideal at any magnification, since perspective remains constant, as does the position of the entrance pupil. However, this is not very practical because there is no practical way to precisely move the rear bellows standard in a repeatable way unless you have a very light touch of the positioning knob. Also, the only company today that makes a bellows with an adjustable rear standard is Noflex, and with the necessary camera and lens adapters, price is close to $900. An alternative on the used marker are the beautiful Nikon PB-4 and PB-6 bellows.

Note than at high magnification the step size by moving the rear standard can be larger that what is required for moving either the front standard or a focusing rail, since the depth-of focus is greater that the depth-of-field, and that relationship grows with magnification.

Moving the front standard on a bellows is like moving the focusing ring on a lens; magnification changes slightly, but is inconsequential for small subjects and is easily handled by stacking software.

Practically: Handholding in the field, there is the gliding-into-focus technique, or auto-focus bracketing if practical on your camera. As noted above, the autofocus bracketing might provide fewer stacking artifacts. On a tripod, again, autofocus bracketing or manually turning the focusing ring (if you have a lens with a nice long focus throw and have a deft touch). The gliding-into-focus technique can be used above 1X, whereas the other possibilities are limited to 1X (or maybe somewhat above when using a teleconverter or automatic extension tube).

For tripod work above 1X, a focusing slide is really the only practical solution.

For what it’s worth, modern macro lenses (the 1X autofocus variety) achieve magnification not by lens extension as in the old days, but by changing (shortening) the effective focal length of the optics. Technically, this changes the magnification a bit, but it’s inconsequential for our purposes. But what is consequential, is that for many lenses, the change in focal length can be as much as 25-30% less, with attendant effect of working distance; your 105mm macro lens maybe more like 80mm at 1X.

Here’s something to consider. Stacking artifacts become more prevalent as depth-of-field decreases. If you close the lens down by two stops, D-O-F doubles, which noticeably decreases artifacts, and cuts the number of required steps sizes in half. I know, diffraction, diffraction, diffraction , but modern post-production sharpening algorithms are quite remarkable, so it’s something to consider. Everything is a trade-off. And then there’s Photoshop.

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

www.MacroPhotographer.net

I am using a Swebo ArtsCaptor as bellows with my Hasselblad 907X and a Mejiro FL0530 110mm/4.0 lens (that lens can only be stoped down to f8.0 but I use it mostly at 5.6) and the bellows can be installed in both directions to allow movement of the front or rear standard (that's what I use as I do the same with my large format camera). Rear standard focusing work fine with that setup up to 2X. That lens allows even more magnification but that what I can achieve with maximum extension on the bellows. I could add some extension tube but using a lens with less focal length would be more practical. The Novoflex Castel micro motorized can accept bellows with rear focusing and step size can be programmed for rear standard movement but that system is just too expensive for me.

My question is more about lens design of contemporary macro lenses. Even the lenses which have internal focusing and keep the distance of front of lens to subject constant the entrance pupil may or maybe not fixed therefore the perspective could be constant or changing. For a very short time I tested the OM 90mm/3.5 macro and the Lumix S 100mm/2.8 and I found more stacking artifacts using both methods of Zerene with OM one. So I suspect it may have something to do how the entrance pupil is behaving.