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DoF scale on Zeiss Zm lens on T

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I have a Biogon 28mm f2.8 on my T - does anyone know if the DoF scale is true as this is a full frame lens on a APS-C crop sensor. Smaller sensors have greater DoF so may it is even deeper than the scale shows - or not as the sensor less than the full frame image circle which is not affected. Great combo but the M-L adaptor adds cost of course. THANKS !

I use a Zeiss 21mm Biogon on my T, and only focus by DoF markings. Equivalence occurs when the markings are read at just over -1 f/stops. In other words, if shooting at f/8, I'll set the focus at slightly less than f/5.6.

 

As Gordon said, depth of field applies only for one particular print size. I thinks he's right when he states it's for an 8x10 print. One of the reasons people don't like reading focus from their lens barrel is because when they view the image at 100%, the markings have lied. But really, they haven't!

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As Gordon said, depth of field applies only for one particular print size.

No, of course it doesn't.

 

Instead, it applies to a certain relation between print size (or more generally, viewing size) and viewing distance. The common convention of max. circle of confusion = 1/1,500th of the sensor or film format assumes a viewing distance that's about equal to the diagonal of the print ... or monitor or display or whatever.

 

By the way, that's the same viewing size-to-distance ratio that makes normal lenses appear normal.

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Could I simplify the question I asked. If the aperture is set to f8, assuming that IF there is a difference due to sensor size it is one stop, should I read off f5.6, f8, or f11 ? All answers very welcome. This is not just theory but a genuine enquiry - the difference between 5.6 and 11 is a lot. I will try it anyway and see what seems to be correct but I hoped for a simple answer !

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Could I simplify the question I asked. If the aperture is set to f8, assuming that IF there is a difference due to sensor size it is one stop, should I read off f5.6, f8, or f11 ? All answers very welcome. This is not just theory but a genuine enquiry - the difference between 5.6 and 11 is a lot. I will try it anyway and see what seems to be correct but I hoped for a simple answer !

 Just under f/5.6; one third to one half a stop between it and f/4.

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No, of course it doesn't.

 

Instead, it applies to a certain relation between print size (or more generally, viewing size) and viewing distance. The common convention of max. circle of confusion = 1/1,500th of the sensor or film format assumes a viewing distance that's about equal to the diagonal of the print ... or monitor or display or whatever.

 

By the way, that's the same viewing size-to-distance ratio that makes normal lenses appear normal.

I recall that at 8x10, the viewing distance would be that at which a person standing at the light table, looking down at the print, would see nothing discernibly out of focus at the appropriate DoF. The idea that viewing distance and print size has a relationship, is good and proper.

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I use a Zeiss 21mm Biogon on my T, and only focus by DoF markings. Equivalence occurs when the markings are read at just over -1 f/stops. In other words, if shooting at f/8, I'll set the focus at slightly less than f/5.6.

 

As Gordon said, depth of field applies only for one particular print size. I thinks he's right when he states it's for an 8x10 print. One of the reasons people don't like reading focus from their lens barrel is because when they view the image at 100%, the markings have lied. But really, they haven't!

traditionally Leica DOF lens scale was for  13 x 18 cm. 

you gain Schärfentiefe/Tiefenschärfe when cropping the negative and enlarge to same size ( that is why we used KC25 or TechPan in the old days )

When you cropped a 35mm neg shot with a 50mm lens to get a 200mm crop you arrived at the DOF of a 100mm lens.

Grain and enlarger lens sharpness were the limiting factor in those days

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Traditionally, Leica depth-of-field lens scale was for  13 × 18 cm.

Nonsense.

 

 

You gain Schärfentiefe when cropping the negative and enlarge to same size ...

Nonsense.

 

 

... (that is why we used Kodachrome 25 or Technical Pan in the old days).

Nonsense.

 

 

When you cropped a 35-mm-format negative shot with a 50 mm lens to get a 200 mm crop you arrived at the depth-of-field of a 100 mm lens.

Oops!? For a change, this is true.

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Nonsense.

 

 

 

Nonsense.

 

 

 

Nonsense.

 

 

 

Oops!? For a change, this is true.

Your discussion style is a bit abrupt - and unnecessary.

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Your discussion style is a bit abrupt—and unnecessary.

It's just because people keep repeating the same nonsense over and over—even within one single thread.

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No, of course it doesn't.

 

Instead, it applies to a certain relation between print size (or more generally, viewing size) and viewing distance. The common convention of max. circle of confusion = 1/1,500th of the sensor or film format assumes a viewing distance that's about equal to the diagonal of the print ... or monitor or display or whatever.

 

 

Of course you are correct in how the CoC is calculated. However I am confident that the original DoF calculations were based on a 7x5" print and this was later amended to a 10x8 at 12" VD (as I posted earlier). Possibly because a number of people involved couldn't actually focus on the smaller print and viewing distance. The original CoC sizes were eyballed based on these "standards" to arrive at the approximately 1/500th figure you cite. I think the actual math was derived from these original "standards" which are essentially just made up by a bunch of old blokes in a room. I can't cite a source but I'm reasonably confident I have my facts straight.

 

Gordon

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Reckon you are right Gordon...

 

With pixel peeping everyone has different expectations.  Throw it all out the window...except for super wides, then it all works...

 

all best

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I am confident that the original depth-of-filed calculations were based on a 7 × 5" print and this was later amended to a 10 × 8" at 12" viewing distance (as I posted earlier). Possibly because a number of people involved couldn't actually focus on the smaller print and viewing distance. The original CoC sizes were [...] essentially just made up by a bunch of old blokes in a room.

 

[...] I'm reasonably confident I have my facts straight.

 

Facts. Straight. Ugh ...

 

People a hundred years ago weren't half as dumb as you think they were. They weren't The Flintstones, you know?

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[...]

All this exact shit about circle of confusion nobody cares about since nobody prints large anymore anyway. [...]

 

How does one rationalize using a medium format digital camera?

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