J12 DOF Scale

[Peter_Jones]

Is the DOF scale on Jupiter 12 lenses reasonably accurate , or should it be taken with a pinch of salt ?

 

[kb244]

I think most Russian 'measurements' so to speak should be taken with a grain of salt, much like the aperture might be off half a stop or so

Also since you're talking bout depth-of-field scale, that all depends on what do you consider acceptably sharp near-and-far and what did the manufacture consider acceptable?

Theres an easy way to see if it least matches the 'standard' math used by it.

Let's say erm, f/5.6 focused at 4meters
A DOF calculator would tell you

Near limit 2.58 m
Far limit 8.87 m
Total 6.29 m
In front of subject 1.42 m (23%)
Behind subject 4.87 m (77%)
Hyperfocal distance 7.25 m
Circle of confusion 0.03 mm


Now if I put the focus ring on 4m, the right side of 5.6 is 15 meters, and the left side is between 2 and 2,5 meters. So if I redo it for f/2.8 near on the calculator would be bout 3.14 and far would be about 5.5m, but on the J-12 shows near being between 2.5m and 3m, and far being about 6-7m.

So from that we can assume that the 'edges' of the DOF scale goes beyond what is considered the range via mathematics.

In other words, take the near/far with a grain of salt and give yourself say a 10 to 15% shorter range to be on the safe side.


Now considering manufacturing variation, your J-12 might have different landing points than mine does as far as the DOF scale goes.

Try some calculations for yourself over at dofmaster.com

 

[ben lloyd]

I have a silver J-12 in LTM, *as a rule of thumb* I find the markings about a stop too generous, this is in comparison too other (mostly more modern) 35s I have/had.

ie. if shooting at f8, I'll use the f5,6 marks on the barrel

 

[wolves3012]

I have a silver J-12 in LTM, *as a rule of thumb* I find the markings about a stop too generous, this is in comparison too other (mostly more modern) 35s I have/had.

ie. if shooting at f8, I'll use the f5,6 marks on the barrel

That tends to be my tactic too. Covers hasty focussing and other errors.

 

[wolves3012]

Is the DOF scale on Jupiter 12 lenses reasonably accurate , or should it be taken with a pinch of salt ?

DOF is arbitrary since it doesn't really exist - a lens focusses sharply in a flat (ish) plane only. The DOF scale is a guide and is based on a certain size of the circle-of-confusion to give "acceptable" sharpness in a print. That also depends how large the print is and how far you view it from (not to mention your eyesight standards!). Some will say it should be based on 0.03mm, others 0.05mm and so on. What's acceptable to you may not coincide with my idea (or vice versa). Better to err on the side of safety if the sharpness matters to the desired result.

 

[Tair-11A]

Is the DOF scale on Jupiter 12 lenses reasonably accurate , or should it be taken with a pinch of salt ?

I think there are NO any problems with accuracy on Jupiter 12, especially if you have GOMZ lens or black Litkarino's lens

 

[rxmd]

I think most Russian 'measurements' so to speak should be taken with a grain of salt

I don't.

In addition, if you will bother to take the time looking at the DOF scale of a pre-war Zeiss Biogon, or comparing the DOF scales on a pre-war Contax and a post-war Kiev body, you will find that the Russian 'measurements' are every bit as precise as the German ones.

Theres an easy way to see if it least matches the 'standard' math used by it.

Let's say erm, f/5.6 focused at 4meters. A DOF calculator would tell you...

Aha.

The fact that you have so many online DOF calculators at your disposal nowadays tends to give the false illusion that DOF is something absolutely set in stone. It isn't.

Soviet DOF scales were calculated for smaller print sizes, where DOF appears bigger when viewed from the same distance. (Since Soviet Man had about the same arm length as any other human, the latter can be reasonably assumed). So the DOF scale, and an Internet DOF calculator are based on different sets of assumptions when an image is sharp.

So by your little calculating example you are in fact proving nothing about the adherence to "the 'standard' math used by it", you are just discovering for yourself that there are different ways of calculating DOF.

In practice, with Soviet lenses I tend to give them 1 to 1.5 extra stops, given that I usually print in 18x24 while the prints I see in Soviet family albums are very rarely larger than 10x15 if at all, and in old albums it's not rare to see 7x10s.

Philipp

 

[Tair-11A]

in old albums it's not rare to see 7x10s.

9x12 cm - old soviet format

 

[Roger Hicks]

9x12 cm - old soviet format

Not just Soviet. This is the standard European equivalent to 4x5 inch (10,1 x 12,7cm) and is sometimes known as 'European quarter-plate' (3,25 x 4,25 inch -- about 8,8 x 11cm).

Pre-war Zeiss d-o-f scales sometimes assumed postcard size enlargements and were therefore correspondingly more generous than, say, Leica which probably assumed 12x18cm or even 16x24cm. The FSU d-o-f scales were almost certainly exact copies.

Cheers,

R.

 

[kb244]

The fact that you have so many online DOF calculators at your disposal nowadays tends to give the false illusion that DOF is something absolutely set in stone. It isn't.

Well did I not already say DOF was subjective depending on your "Acceptable" and someone else's acceptable.

 

[payasam]

After some rolls you will not need to look at the depth of field markings. As to your question, yes, the markings on the J-12 are good enough.