How To Use Diaphragm With Mitty Lenses

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lonepal
Posts: 320
Joined: Sat Jan 28, 2017 12:26 pm
Location: Turkey

How To Use Diaphragm With Mitty Lenses

Post by lonepal »

Hi;

I am currently using a Mitutoyo 5X with a Sigma LSA and also a diaphragm between them.
All of them mounted in front of a Pentax bellows.
Sensor-Sigma LSA=200mm
Mitty-Sigma LSA=76-77mm

Source for Mitty-Sigma distance;

http://www.photomacrography.net/forum/v ... c&start=22

I made some trials but I think I lost details when I close the aperture a bit.
I think this is because I am so close to the diffraction limit.

Is it useful to use a diaphragm with Mitty lenses?
If so, how do you use it?

Please advice me about using it.
Thanks.
Regards.
Omer

ChrisR
Site Admin
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Joined: Sat Mar 14, 2009 3:58 am
Location: Near London, UK

Post by ChrisR »

You will lose resolution when you close the aperture.

Two uses -
#1) when you only need a small picture, perhaps 1000 pixels wide, so you can use a smaller aperture for more DOF. You wouldn't see the finest detail anyway.

#2) more usefully, to add frame(s) at the end of the stack. This makes the transition from sharp to blurred much more gradual, and out of focus background features become recognizable. If you mark your aperture ring so you can reliably set, say, 4 stops smaller, then you can increase the exposure by that amount.
Align the extra frame but don't include it in the stack. Re-stack it with the output image, afterwards. The reason is that in-focus details will appear in strange places, which you don't want.
Chris R

lonepal
Posts: 320
Joined: Sat Jan 28, 2017 12:26 pm
Location: Turkey

Post by lonepal »

Thanks Chris.

This is very useful information for me.
I will use the diaphragm as you told.
Regards.
Omer

dolmadis
Posts: 719
Joined: Wed Dec 07, 2011 1:51 pm
Location: UK

Post by dolmadis »

ChrisR wrote: If you mark your aperture ring so you can reliably set, say, 4 stops smaller, then you can increase the exposure by that amount.
I am sorry but I am struggling to understand the procedure.

HELP !!

BR

John

Adalbert
Posts: 1139
Joined: Mon Nov 30, 2015 1:09 pm

Post by Adalbert »

Hi Chris,
What do you think about that:
#3: to look for the interesting object/detail with the closed iris and to take the photographs with the open one
BR, ADi

Lou Jost
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Joined: Fri Sep 04, 2015 7:03 am
Location: Ecuador
Contact:

Post by Lou Jost »

Adalbert, if I may chime in, that is a very good use for an iris. There are often surprises in the construction of a stack, since not all elements of the subject are visible at the same time. An iris increases the odds that you'll see the whole composition correctly.

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