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Archive 2013 · Adapters with Iris ...

  
 
RustyBug
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p.1 #1 · p.1 #1 · Adapters with Iris ...


I was looking at adapters and found Fotodiox adapters with an iris. Looks like it would be an interesting way to stop down without an electronic interface for lenses without manual aperture rings.

My is what changes will occur by controlling the aperture after the rear element (i.e. closer to the film plane) rather than between elements ... to drawing style properties like contrast, vignetting, dof, bokeh, diffraction, etc.?



Dec 11, 2013 at 01:03 PM
JohnJ
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p.1 #2 · p.1 #2 · Adapters with Iris ...


In the old photographic manuals, such as the 'Dictionary of Photography', they would often refer to flare spots which could be caused by improperly positioned apertures. Not sure if the aperture being behind the lens can cause the same fault, but it's worth considering.

Eg of a flare spot:
http://photocornucopia.com/images/Lenses/Meogon/IMG_6057_Meo80_2F8.gif



Dec 11, 2013 at 01:36 PM
briantho
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p.1 #3 · p.1 #3 · Adapters with Iris ...


I have an adapter with built in Iris for Contax N which I've used on NEX. The only effect closing the iris on the adapter has is to cause vignetting, there is no change in DoF or sharpness.


Dec 11, 2013 at 02:38 PM
RustyBug
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p.1 #4 · p.1 #4 · Adapters with Iris ...


You say no impact to dof ... does that mean that since all shots would be wide open at the lens itself (absence of being electronically controlled), that all shots with a given lens would have the same dof ... as say all @ f3.5 in the case of the 24L TS-E II or all @ 1.8 for a 50/1.8 without manual aperture ring.


Dec 11, 2013 at 04:37 PM
mcbroomf
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p.1 #5 · p.1 #5 · Adapters with Iris ...


Just say no!

These effectively just act as masks as Briantho mentioned.



Dec 11, 2013 at 05:04 PM
RustyBug
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p.1 #6 · p.1 #6 · Adapters with Iris ...


So, you're 100% WO then for IQ purposes ...


Dec 11, 2013 at 05:54 PM
jcolwell
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p.1 #7 · p.1 #7 · Adapters with Iris ...


Here's some examples of the effect on DOF of an iris in front of the lens, using a Copal 3 shutter and Canon 6D.

When used, the Copal No. 3 shutter is set to f/8, which is correct at "f/8" for some unknown reference focal length.

The first set shows the ZE 50/2 at f/2, without and with the Copal at f/8, handheld with finder manual focus. The third image in this set shows the extreme vignetting with the Copal at f/8. This is because the Copal 3 has a 62mm back thread, while the ZE 50 has a 67mm front thread; the Copal 3 sort of fits inside the lens filter ring.

The second set is a bit more well-controlled, with a Mamiya 645 C 80/2.8 N at f/2.8 on 6D, with tripod, 2 sec timer, and LiveView manual focus. The last image in this sequence shows the Copal No. 3 shutter, camera, and propses.







ZE 50 f2 at f/2, no Copal shutter, cropped







ZE 50/2 at f/2, Copal No. 3 shutter at f/8, cropped







ZE 50/2 at f/2, Copal No. 3 shutter at f/8, full image



Edited on Dec 11, 2013 at 08:08 PM · View previous versions



Dec 11, 2013 at 07:46 PM
jcolwell
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p.1 #8 · p.1 #8 · Adapters with Iris ...


Here's the second set.





M645 C 80 f2.8 at f/2.8, no Copal shutter, whole image







M645 C 80 f2.8 at f/2.8, Copal No. 3 shutter at f/8, whole image







M645 C 80 f2.8 at f/2.8, no Copal shutter, ~50% crop







M645 C 80 f2.8 at f/2.8, Copal No. 3 aperture at f/8, ~50% crop







Props and gears, Copal No. 3 aperture set to f/8




Dec 11, 2013 at 07:50 PM





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