ruilourosa
Member
Seems the dof scale is well over optimistic, by, at least one stop, have you notest?
Cheers
Cheers
retinax
Well-known
Well it's a press camera, presumably the dof scale assumes rather small reproduction? I've also noticed that a Jupiter 8 and a canon 50 1.8 ltm differ by one whole stop in their dof scale... it's pretty arbitrary really.
oftheherd
Veteran
I'm not sure what you mean, but at http://www.cameramanuals.org/mamiya_pdf/mamiya_press_super_23.pdf at page 57, you can find dof for all the Mamiya Press lenses except the 250 f/8. Are you talking about the dos scales provided by Mamiya, or the markings on the lens?
ruilourosa
Member
Markings on the lens!
ruilourosa
Member
focusing to the hyperfocal distance and putting the edge of infinity mark on the chosen f stop will not provide enough DOF to reach the infinity, infinity will be out of focus... the lens is fine tuned and the focus is being checked in the ground glass accessory and on film!
john_s
Well-known
You can compare the markings on the lens with DoF tables to work out approximately the circle of confusion (degree of unsharpness) used in the calculation. They are generally misleading because of poor detail at the extremes of the "depth of field". With experience, you pick the appropriate aperture for the sharpness you expect. A rule of thumb for me is to use the marks for 2 stops wider. If that results in not enough DoF then it's time to re-evaluate the composition.
ruilourosa
Member
Composition?
Bob Michaels
nobody special
ColSebastianMoran
( IRL Richard Karash )
Not the first time I've seen DOF markings on a lens that were optimistic.
Bob notes the math calculation, and this depends hugely on the criteria built into the calculation. If you are willing to accept a bigger circle of confusion, the math will give you a wider DOF range. And, vice-versa.
Also note the important comment of Bjørn Rørslett: DOF is subjective and perceptual.
To me, the calculations and lens markings are only a guide.
Bob notes the math calculation, and this depends hugely on the criteria built into the calculation. If you are willing to accept a bigger circle of confusion, the math will give you a wider DOF range. And, vice-versa.
Also note the important comment of Bjørn Rørslett: DOF is subjective and perceptual.
To me, the calculations and lens markings are only a guide.
Canyongazer
Canyongazer
"DOF is subjective and perceptual."
Yup.
Yup.
Dwig
Well-known
True, to a degree.
It becomes quite mystical since "acceptable circle of confusion" is not anything that can be measured. It is pure whimsy what any one photographer would consider "acceptable". Camera format, intended print size, and printing method all influence the acceptability of any one CoC, but still it is a very personal choice what is "sharp enough".
john_s
Well-known
If the picture isn't going to work because there isn't enough DoF then I reconsider the composition. I might decide to change the viewpoint to rely less on the background that's too far out of focus, for example.
john_s
Well-known
Also, the circle of confusion is an approximation to the reality, where the point of focus is assumed to be a point but it isn't exactly a point. It is a complex three dimensional curve. Look up "caustic" in the context of optics.
One of the variables of DOF lens markings is the print size.
Most lenses thru the 1970's had DOF markings based upon a 4x5" print
Rule of thumb was stop down two stops for an 8x10 print
4x5 print DOF markings are probably the same even today.
Most lenses thru the 1970's had DOF markings based upon a 4x5" print
Rule of thumb was stop down two stops for an 8x10 print
4x5 print DOF markings are probably the same even today.
ruilourosa
Member
i know the math, and i understand the principle, just wandering if anyone had the same issue...
cheers!
cheers!