Depth of field

Regarding "DOF," I will leave it to the physicists in the audience to explain the difference between Depth of Focus and Depth of Field. 😉

I think the most valuable concept yet presented in this thread is that lens markings are based on assumptions, and in general are but guidelines.

I think what many are in search of is the Magic Formula that will produce the Perfect Image, without further intervention on the part of the photographer; as if art could be distilled down to some mechanical process, starting with pushing a button and ending with Fine Art spewing forth from one's printer, without trial and error and labor the intermediary. Yes, I too would like for the process of image creation to be as goof-proof as possible, but one must understand the limits of the process through experience just as much through mathematical calculation.

~Joe
 
oftheherd said:
My VAGs don't have DOF markings, but then I guess it is figured they don't need it. You are correct on the 1/3 in front and 2/3 behind according to all I have read. I don't think I have ever seen a lens marked that way. They are always equal distance on either side of the middle mark.
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That's because the distance scale is not linear. If you look at the distances, 1/3 to 2/3 is about right. Example: Take the distance and DOF scale on a Contax body (which, because of the in-body helical, is the same for all 50mm lenses). Distance set at 8 feet gives you a DOF at f/8 from 6 to 12 feet, i.e. 2 feet in front of and 4 feet behind your set distance. Hence, 1/3 to 2/3.
 
This problem is caused by photographers using lenses instead of pinholes to create their images.

Just quit using them, and switch to pinholes.
 
Quite useful on my Vito II with no rangefinder (and not even an accessory shoe to attach my separate rangefinder!). Also useful in the same way when scale focusing with one of the Lynx (Lynxes?).
 
bigeye said:
It seems to reflect the times. I'm playing with an Isolette-Speedex, which was considered serious hobbyist camera in its day and it doesn't have any focusing aids at all. It was accepted to use DoF as your sole means of focusing in the early '50s.

It has to do with the modern fixation with metric measurement.

In the '50s, image quality was measured bluntly in furlongs, hogsheads, and firkins. Then the British accepted the precision of an old French measurement system, and look what happened.

- Charlie
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They wanted base ten weeks and months, that did not work out so well.
;-)

Actually almost all systems are precise, the easy one that is a real system is the SI (Metric) system.

Avoirdupois is the French name for the British system only used, to some extent, in America. It is not a system at all, just many other units converted to each other with different meanings often attributed to the same name. Plus, we have begun to avoid fractions, and go to a decimal to toss in the mix, e.g. 1.34 " .

As for the British adopting the SI system, they did so legally, but not for real for a long time.

Roger will explain Whitworth (spelling?) as I am sure he worked on more than one bike or car with that system-- lots of fun, especially if you lose a bolt and really need to put it back.

I did have one problem with the SI system recently, I was zone focusing with my Collapsible Summicron, and after a few shots I noticed it was marked in m, not Feet, so I had a few very soft images.

Regards, John
 
I have only checked my DOF marks a couple of times--ever. I know about what each aperture will give me, at each distance, and I learned it from printing 8x10s with notes of settings. Never did I really understand why so much clutter atop the lens barrel was necessary considering how insufficient those measurements are.
 
charjohncarter said:
I love just having DOF control available. It was even more fun when I shot Kodachrome 10 & 25.
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Efke KB25!
JohnTF said:
Roger will explain Whitworth (spelling?) as I am sure he worked on more than one bike or car with that system-- lots of fun, especially if you lose a bolt and really need to put it back.
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Whitworth is great! Never have to pull out my helicoil kit on old Brit bikes -- different story on my old Jappers! The amount of M8 and M10 metric fine coils I've had to tap...

Only thing is, lose a nut, try finding a new one at the fastener shop.
 
Right, on the MG TD we were rather careful with losing nuts and bolts, took a year to rebuild the motor-- it had been supercharged, needed oversize rings, a rebore, regrind on the crank, etc. We actually had some Sears wrenches marked with a "w".

The MG I have now is straight Avoirdupois I think, have a metric crescent wrench as well, it's 300cm long.
 

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Whitworth we used on the farm and soft metal, PROPER motorbikes and cars use BSF, lesser machinery used NC ,NF . Still have full set of "pommey" taps and dies. Of course just like practical use of D.O.F. I now use all metric and a very long spanner (they dont work loose !)

cheers.

ron.
 
CoC is important. Hasselblad suggests that for large prints, one uses the CoC for 35mm rather than the markings on the lens barrel.
 
Yes

Yes

Freytag's '69 book "The Hasselblad Way" recommended .06mm coc for standard work, and .03mm for "critical work"

Leica's DOF lens markings are based on .023mm making them perfectly suitable for APS-C, APS-H, and legacy medium sizes.

Pico said:
CoC is important. Hasselblad suggests that for large prints, one uses the CoC for 35mm rather than the markings on the lens barrel.
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I have always thought of narrow DOF as an isolation tool (focus isolation) which is useful when the relationship between the subject and background isn't attractive. If you can't get narrow DOF (as with small formats), then you need to pay attention to the background's relation to the subject. How you go about depends on the final output size and probably your viewing audience. Knowing the COC stuff can be very usefull, but mostly at the intuitive level, because unless you can shift from analytic to creative mind-set and back, you could lose the moment.
If you got to have DOF control one of the best tools is a DSLR with a legacy lens attached that is used at operating aperture.
Bob
 
The oldest bits of the Land Rover (the gearbox, originally designed in the 1930s) use Whitworth, but otherwise it's mostly split between BS/BSF and metric - though AF spanners often work, because many have the same jaw dimensions AF as BS/BSF and even Whitworth. Of course part of the electrical system is BA...

The big advantage of a real car is that you can still get bits for it, but to make life REALLY interesting, three of the bleed nipples on the slave cylinders are metric and the other is BS or possibly AF.

Cheers,

R.
 
Bob Ross said:
I have always thought of narrow DOF as an isolation tool (focus isolation) which is useful when the relationship between the subject and background isn't attractive. If you can't get narrow DOF (as with small formats), then you need to pay attention to the background's relation to the subject. How you go about depends on the final output size and probably your viewing audience. Knowing the COC stuff can be very usefull, but mostly at the intuitive level, because unless you can shift from analytic to creative mind-set and back, you could lose the moment.
If you got to have DOF control one of the best tools is a DSLR with a legacy lens attached that is used at operating aperture.
Bob
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Part of being on your game, just as having focus zone set, knowing which way to turn the lens, choosing focal length, angle of view, -- all tools.

A bit of simplicity in isolation-- I do not care for many "busy" backgrounds with bright areas to draw the eye somewhere distracting to the image you want.

Some days it just seems you see all of this with the right subjects, and then there are the others, and the circle of confusion includes everything.

Often a disappointment when you cannot get position, or your equipment lets you down.

Regards, John
 
Roger Hicks said:
The big advantage of a real car is that you can still get bits for it, but to make life REALLY interesting, three of the bleed nipples on the slave cylinders are metric and the other is BS or possibly AF.

Cheers,

R.
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Perhaps telling you which could be rebuilt and which were replaced?

Ford had a nasty habit of using ones much too small, 1/4" and with our winters, and salt, would break off-- bled one cylinder with a .004" feeler in the top of the cup, lasted longer than the car. The really right tools were then purchased for the next go around. Noticed the MG had 3/8" plated screws on a much smaller car.

Don't think many places rebuild much these days.

I know you like terms, perhaps you have not been told a Ford Wrench is a large hammer.

J
 
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xwhatsit said:
Efke KB25!

Whitworth is great! Never have to pull out my helicoil kit on old Brit bikes -- different story on my old Jappers! The amount of M8 and M10 metric fine coils I've had to tap...

Only thing is, lose a nut, try finding a new one at the fastener shop.
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Aside - When Triumph motorcycle switched metrics, they went to American Standard. I think it was 1973. Very odd choice since America was considering metric at the time.
 
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