Iskra - depth of field markings

[Diomedes]

I'm using a nice Iskra converted from 6x6cm to 6x4.5cm. Can I expect problems with the depth of field markings on my lens and hyperfocal distance because of different formats?

Regards,
Vjeko

 

[rxmd]

DOF behaviour will be different, depending on the shape of the final print. An equally-sized square print will have slightly different DOF from 6x4.5 because you have to print from a 4.5x4.5 negative region in the center. Non-square prints from 6x6 are crops anyway, so it won't matter. At any rate the difference won't be big.

 

[Abbazz]

Vjeko,

You have to be very careful with the DOF markings on these old cameras. Usually, they were calibrated for contact prints or small enlargings. If you use them for pictures that will be enlarged 5x or more, you will be disappointed with the lack of sharpness. To get optimal sharpness, use the DOF markings 1 or 2 stops below your current aperture. For example, if you shoot at f/11, use the DOF markings for F/8 or even F/5.6 on the lens scale.

Cheers,

Abbazz

 

[Diomedes]

Thanks!

 

[rover]

I believe jmc56 wanted to share this

The format change per se doesn't affect the focus or the depth of field. That's governed by the flange to focal (film) plane specification of the lens as supplied. As long as you have the original lens and the film plane is in the same place, the focus has NOT changed. There's a slight telephoto effect, but it's almost irrelevant given that most prints are rectangular from the same area

I have several dual format cameras, e.g. Moskvas IVs, which were built to do this with a pop-in film mask and dual ruby windows for 6x9 or 6x6. There is no focus change. So far as I can tell this 4.5 format is always a hack with an Iskra.

It's possible that the format was modified just because the user preferred it for lower costs, but usallly Iskras with ruby windows had worn or damaged advance mechanisms. It was easier to bypass some features and add the ruby window. They may be repairable. but it requires someone who has the knowledge and the parts. I have several in various states of repair from good to newly overhauled (two enroute from OK) but I want to avoid the ruby window.

The Iskra has an excellent rangefinder with plenty of beam and is a match for my Agfa Super Sillette with my limited tests of it. It's a bit chunky for the 4.5x6 format. Haven't done anything with the film yet, but did some shots last week (while using digital for most) and reinforced my impressions. When the advance is working properly, it makes testing a pain, but in use it's a pleasure.

Some classic cameras did require focus changes, either because a back swap (from roll to sheet) moved the film plane or the lens was a dual focal length (which affects DOF). But this one is pretty simple.