DOF marking - serious reference or engraved for fun?

[ForestCap]

Hi,

I was doing some cleaning work of my Industar-22 and 50 collapsible lenses. I noticed that the DOF markings on a pre-1950 Moskva version Industar-22 and a 1950s Industar-50 are quite different from each other, even though they are basically the same lens (Tessar) with almost identical focus length, and almost identical distance markings, focus-throw, etc.

As seen in the attachment photo, according to the DOF markings respectively, the Moskva I-22 lens(on the left ) apparently would give shallower DOF than the 1950s I-50(on the right), since the covered distance marking would be smaller at a given aperture value on the I-22.

Does anyone know why the difference? Was it because that the tolerance of un-sharpness increased from the 1950s on (hence the deeper suggested DOF)?

Please throw in your thoughts. Thank you!

 

[sevo]

Are you sure the focus throw is the same? If it is, they used a smaller CoC for the later lens. Which does not sound strange, as the film resolution increased considerably at that time.

 

[David Hughes]

Apologies for being ignorant but isn't the Moskva a 120 film camera taking a 6x9cm negative? In which case the magnification would be less critical and would it have a 50/53mm lens?

Enlightenment please.

Regards, David

 

[ForestCap]

Are you sure the focus throw is the same? If it is, they used a smaller CoC for the later lens. Which does not sound strange, as the film resolution increased considerably at that time.

Hi sevo, yes I'm sure the throw is the same. Your explains makes most sense to me now. Thanks.

Apologies for being ignorant but isn't the Moskva a 120 film camera taking a 6x9cm negative? In which case the magnification would be less critical and would it have a 50/53mm lens?

Enlightenment please.

Regards, David

Hi David, by Moskva version I meant the PT5715 by SovietCamera:
http://www.sovietcams.com/index.php?804100465
It's just an uncoated Industar-22 with "Moskva" engraved on the front of the lens, I think it was for FED-Zorki and maybe early Zorki-1.

 

[Dwig]

Are you sure the focus throw is the same? If it is, they used a smaller CoC for the later lens. Which does not sound strange, as the film resolution increased considerably at that time.

Its more likely a CoC change to reflect usage trends than for any actual film resolution change. Choice of an appropriate CoC involves an assumption on the print size and, at least in the US, that was a distinct change is the commonly made print sizes between the '50s and the '70s that had nothing to do with the film's capabilities. In the '70s, more people more often enlarged their 35mm images, B&W and Color, beyond the typical 3-1/2x5 the in the '50s.

 

[shawn]

There is an online calculator for DOF at:

http://www.dofmaster.com/dofjs.html

You could compare it against each lens to see which agrees more. I was just doing this with a Konica Hexar 50mm and the engravings are very close to the calculations.

Shawn