Stacking by autofocus

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Adalbert
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Joined: Mon Nov 30, 2015 1:09 pm

Stacking by autofocus

Post by Adalbert »

Hello everyone,

Does anybody know if my idea is OK?

I would like to connect the CANON EF 70-200L to the NIKON CFI 10x (infinite) and focus for the stacking by using of the autofocus controlled by the software.

I have already asked for that but in a wrong thread :-(
http://www.photomacrography.net/forum/v ... sc&start=0

Thank you in advance.

Best regards,
Adi

rjlittlefield
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Post by rjlittlefield »

And so here again is the answer that I gave you over there.
Adalbert wrote:Would you tell me please if you can set the focus automatically using e.g. Helicon Remote ?
This works well, within certain limits, if the rear lens uses internal focusing so that the objective does not move.

See http://www.photomacrography.net/forum/v ... hp?t=14569 for discussion.

--Rik

Adalbert
Posts: 1192
Joined: Mon Nov 30, 2015 1:09 pm

Post by Adalbert »

Hello Rik,

The other thread was my introduction, so I started a new one here :-)

Yes, CANON EF 70-200L is such one, so it should work without any limits.

What about the software? What would you recommend?
I only have tested the android app “Helicon Remote” up to now, because it is for free.

Thank you in advance.
Bye, Adi

rjlittlefield
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Post by rjlittlefield »

Adi, I do not have a strong feeling for what software is best for controlling the motor. I seem to recall that I did some quick testing of Helicon Remote on my Android tablet and found that it worked as well as any, better than most. Because you've already had success with it, I suggest to keep using it.
CANON EF 70-200L is such one, so it should work without any limits.
There are always limits. In this case the limit will be on stack depth.

When you step focus by changing the lens-to-subject distance, there is no hard limit on stack depth. If your subject is 4 mm deep and you're shooting with a 10X NA 0.25 objective at 0.005mm step size, you just shoot 800 frames. It takes a long time, but it works well.

In contrast, when you step focus by internally altering focus of the rear lens, there is a hard limit that is imposed by the close focus distance of that rear lens. For example if the rear lens will only focus as close as "1 meter", then at 10X NA 0.25 your stack depth will be limited to only about 0.4 mm, say 80 frames.

At higher magnifications there is also a soft limit imposed by added aberrations, as discussed in the other thread.

--Rik

Adalbert
Posts: 1192
Joined: Mon Nov 30, 2015 1:09 pm

Post by Adalbert »

Hello Rik,

Does it mean, that the minimal size of the smallest step of the CANON-USM-motor is still too big for the stacking with the NIKON 10x and If yes, then I have to move the camera or object mechanically with e.g. a StackShot ?

Thank you in advance.
BR, Adi

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