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Olympus in-camera focus bracketing with 10x inf objective
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zzffnn



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PostPosted: Wed Jan 31, 2018 12:22 pm    Post subject: Olympus in-camera focus bracketing with 10x inf objective Reply with quote

I have read, from two members' comments, that Olympus in-camera focus bracketing works with 10x infinity objectives.

One was by Lou, who used Oly 75mm prime with 10x Mitu. http://www.photomacrography.net/forum/viewtopic.php?t=30177&postdays=0&postorder=asc&start=75
But I don't know if he used flash or not. I also need close to 7x on-sensor at least, not 3.75x.

The other was by chuong nguyen, who used (I assume) Oly 40-150 pro F/2.8 and an unknown 10x. Again, don't know if flash is used. http://www.photomacrography.net/forum/viewtopic.php?t=30177&postdays=0&postorder=asc&start=45

My plan is to use Nikon BE Plan 10x or another good budget infinity 10x, along with Oly kit zoom 40-150mm non-pro F/4.0-5.6. Preferably under continuous light.

I know Nikon BE Plan 4x would work with my Oly kit 40-150 at 150mm, without very minors vignetting. But I don't know if Nikon BE 10x would work well, as I assume 10x' image cone might be smaller?

Also there is the issue of vibration under continuous light, which may interfere more at 10x on-sensor than at 4x? Flash can be used when electronic shutter speed is really slow, though it would slow down imaging quite a bit (do I have to use flash at 10x on-sensor)?

Furthermore, as Enrico has mentioned before, using infinity microscope objectives this way may be outside of optical design limits or intents? For 4x and low NA of 0.10 or so, this may not cause visible image degradation. But what about at 10x NA 0.25? I am guessing degradation may be visible, at NA 0.40 (20x or so)?

chuong nguyen mentioned imaging depth issue, when he used 20x infinity objective this way. Though he did not mention any image degradation: http://www.photomacrography.net/forum/viewtopic.php?t=30177&postdays=0&postorder=asc&start=45
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Last edited by zzffnn on Tue Feb 06, 2018 6:08 pm; edited 1 time in total
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Lou Jost



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PostPosted: Wed Jan 31, 2018 3:01 pm    Post subject: Reply with quote

I often use 10x on the sensor with my MFT camera with continuous light. I have to be careful to step softly while acquiring, and must avoid peak traffic times (and periods of vocanic eruptions). That is irrelevant to your own situation, of course. Environmental vibrations depend on your neighbors, your house construction, your ability to keep your family members from running around, the construction of your set-up, etc. The camera adds no vibration whatsoever; that's the beauty of mirrorless fully electronic shutters.

Here is a recent shot of an insect eye on MFT with continuous cross-polarized light:

I think this was with the 7.5x Mitu or 10x Mitu on a 135mm lens. Remember that the field of view is the same on an MFT sensor at a magnification of 5x as on a FF camera at 10x.

When I do use flash, at 1/20 sec, the flash light far outweighs stray environmental light, so with just a little attention to blocking sunlight, there is no intrinsic problem there; camera motion due to the environment can be stopped with fast speedlights.

Remember that in-camera focus bracketing only works for very thin stacks when m is much greater than 1.

When using a rail, flash can speed up acquisition rather than slowing it down, because you don't need to use much "settling time". The flash should be powered by an external battery pack or power supply and used at very low power to avoid charging delays.
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Saul



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PostPosted: Wed Jan 31, 2018 3:34 pm    Post subject: Reply with quote

Lou Jost wrote:
...with continuous cross-polarized light...


Any idea why it did not perform like it supposed to ?
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zzffnn



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PostPosted: Wed Jan 31, 2018 3:49 pm    Post subject: Reply with quote

Lou Jost wrote:
........
I think this was with the 7.5x Mitu or 10x Mitu on a 135mm lens. ......

Remember that in-camera focus bracketing only works for very thin stacks when m is much greater than 1.
.....


Thank you very much, Lou.

Which 135 mm lens did you use for that photo? Was it an auto m4/3 lens (I don't know there is a prime 135 auto m4/3 lens; I only know auto zooms for 135mm).

I guess one may put camera on a long focus rail, refocus after the first set of bracketing, then focus bracket again? Would that overcome the depth limitation?

I know alignment may go off, once focus rail runs after the first bracketing. I am currently doing focus bracketing on a stereo scope focusing arm, which may not be smooth or precise enough (I can see alignment moves off on magnified live view). Would stacking softwares, such as Zerene, provide reasonable rescue in alignment (I know they some of that, would software alignment be enough though)?
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Lou Jost



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PostPosted: Wed Jan 31, 2018 4:57 pm    Post subject: Reply with quote

Saul, if you mean why there are still reflections, I don't set the polarizers exactly crossed, because this produces blue highlights (the polarizers are not perfect). I turn the polarizer on the lens to let a bit of light through, so that there are slight white highlights. I also think this looks more natural. But the partly-crossed polarizers do greatly reduce the glare.
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Lou Jost



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PostPosted: Wed Jan 31, 2018 5:03 pm    Post subject: Reply with quote

This picture was not made with focus bracketing. As I mentioned, focus bracketing at higher m has too shallow a range. I used it here to show you that continuous light pictures are possible at this m. I used a Vivitar/Komine 135m lens, which is a very good and very cheap tube lens.

Maybe moving the rail between bracketed sets would work. Zerene can adjust for alignment but might have trouble with the sudden big perspective change (unless your lens is nearly telecentric).
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zzffnn



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PostPosted: Wed Jan 31, 2018 5:50 pm    Post subject: Reply with quote

Thank you again, Lou.

Understood. I am guessing we can separately stack two bracketed sets, then stack the final two image into one.

What is the largest aperture of your Vivitar/Komine 135m lens, by the way (if there are different versions)?

My lenses (Nikon BE Plan 4x and maybe 10x and Oly kit zoom 40-150mm F/4.0-5.6) are probably not telocentric. And I have seen that perspective change in my experiments, I think.
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Lou Jost



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PostPosted: Wed Jan 31, 2018 6:40 pm    Post subject: Reply with quote

It is f/2.8. I've recommended it to many people. For ten times as much money you can get a better one, the Sigma 135 ART lens. But it is not 10x better.

Quote:
I am guessing we can separately stack two bracketed sets, then stack the final two image into one.


I strongly suspect the jump in perspective between the two sets would confuse the software.
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zzffnn



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PostPosted: Wed Jan 31, 2018 6:53 pm    Post subject: Reply with quote

Thank you, Lou.

I remember reading about using a DIY punctured disc between infinity objective and tube lens. Will look into it.
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jojm



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PostPosted: Thu Feb 01, 2018 1:39 pm    Post subject: Reply with quote

Here are three shots, all using focus bracketing on one or more slices.
With the 10x lenses, selected step focus for bracketing is "5", each slice contains 41 frames and corresponds to a deep of 0.1 mm.
With the 20x lens, selected step focus for bracketing is "8", each slice contains 24 frames and corresponds to a deep of 0.02mm.
As I do not keep old stacks, I cannot tell you for the ones how many slices I did for these examples.
Usually it needs between 2 to 10 slices to cover all the deep of the object.
ZS seems to manage very well perspective changes but sometimes fo a better result I need to use bugslabber to split all the stack in different slice as they were shoot.

Beudantite
FOV 1.3 mm (crop factor 3027/3456)
Olympus E-M5 MarkII
M.ZUIKO 40-150mm+MC 14 at 175 mm
Mitutoyo PLAN APO 10x/0.28


Proustite
FOV 2.5 mm (crop factor 4608/4608)
Olympus E-M5 MarkII
M.ZUIKO 40-150mm+MC 14 at 140 mm
NIKON CFI PLAN 10x/0.25


Carminite (crop factor 4468/4608)
FOV 1.1 mm
Olympus E-M5 MarkII
M.ZUIKO 40-150mm+MC 14 at 150 mm
Nikon CFI PLAN FLUOR 20X/0.45 ELWD

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PostPosted: Thu Feb 01, 2018 2:00 pm    Post subject: Reply with quote

Beautiful images! Thank you for your kind advice, Jean-Marc.
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zzffnn



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PostPosted: Thu Feb 01, 2018 3:29 pm    Post subject: Reply with quote

Jean-Marc,

I forgot to ask:

you said deep subjects usually need 2-10 slices and you used step depth 5 for 10x and 8 for 20x.

Once your first bracketed slice stops, how do you determine where to start for the second slice? Do you look at the last image of the first slice, then start from that focus plane? Or do you go pass that focus plane slightly (how much do you go pass, if you have formula or way to determine), then start again?

Also, I though step size for 20x would be smaller than that of 10x, due to higher NA of 20x. How did you determine step size 8 for 20x and step size 5 for 10x?

I think chuong nguyen used step size 1 for his 4x fly head portrait, though he said he used small step just to be safe. I don't know what step size Lou uses.

I did a trial run with stacked Raynox 150+250 on kit zoom at 150mm (F/5.6) once, using a thin seashell. There it looked like step size 3-4 is about right (every to every other image looked slightly different).

Thank you very much!
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Lou Jost



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PostPosted: Thu Feb 01, 2018 3:58 pm    Post subject: Reply with quote

I use large step sizes. It works backwards from what you would do at m <1. You have to use the entire range of focus to finish a very thin slice. If you use a small step size, the lens is going through many hundreds of steps to get from closest focus to infinity, but the image is not changing much per step. It seems to change less per step as m goes up. I have not made careful tests of this, though.

I have never done such high m as Jojm. It is very interesting to see how well that works. Jojm, could we see a 100% crop of the sharpest of these?
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Last edited by Lou Jost on Thu Feb 01, 2018 4:13 pm; edited 2 times in total
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PostPosted: Thu Feb 01, 2018 4:02 pm    Post subject: Reply with quote

Jean-Marc, how is the image quality without the teleconverter?
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zzffnn



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PostPosted: Thu Feb 01, 2018 8:02 pm    Post subject: Reply with quote

Thank you very much, Lou.

I use 0.5x to 4x most often and would like to know the best step sizes, please.

So for 0.5x and 1x, I should use small step sizes. For example, 2-3, I am guessing? What step size for 2x or 4x on sensor should I use?
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Last edited by zzffnn on Tue Feb 06, 2018 6:08 pm; edited 1 time in total
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