Error of 0.07", far greater than one thickness of double weight paper at 0.015"Another check using the grain focuser on a microscope stage. I racked the focuser up and down then came to the best focus 10 times, calipering the stage height after each best focus.
The results varied, as expected. The standard deviation was 0.076 - inch.
Average missed the original mark by 0.07 inches - about 1 standard deviation low.
Error of 0.07", far greater than one thickness of double weight paper at 0.015"
Kid of, like planning for another four hour show.Bill,
Does all of this remind you of your work in radio?
Error of 0.07", far greater than one thickness of double weight paper at 0.015"
And that says it all - as ever people get themselves wrought into the most extraordinary shapes over notional 'precision' that is so far within the tolerances of the system as to be less than irrelevant, yet cannot manage to control the basic parts of the process that demand nothing more than very moderate & reasonable levels of care/ precision.
Greg, I think absolutely you will have better repeatability and precision with 25x vs my 10x.Bill, you used a focuser that is 10x, I used a 25x model. Do you feel the greater magnification may reduce the margin for error any?
I can say that if you are going to take two shots of something important to get it right, it makes sense to go through each setting independently instead of just firing twice.I might take issue with the suggestion that someone who rests his grain focuser on a sheet of enlarging paper when making a print is likely to be the type of photographer who does not exercise very moderate and reasonable levels of care and precision in other areas of the process. I would have come to the opposite conclusion. Of course, I am not an expert on human behavior.
Bill appears to have convincingly determined, "It does not matter to have paper under focuser", and with 10X focuser there is 0.076" typical error that is often not detected even at f/2.8 The only remaining question is "if using 25X grain focuser, is the margin of detectability reduced?"Greg, your video convinced me that it makes no difference whether there is a sheet of paper in the easel or not but others appear to be convinced that it does.
I'd suggest that those who feel( they might say they know rather than feel) that it does make a difference then here's a suggestion: They should continue to use a sheet of paper and others who find no difference need not bother
After 13 pages it would seem likely that the only reasonable consensus possible here is that we are not going to get to a consensus
pentaxuser
Well stated,
If, when shooting a photo of flat art, my subject is at exactly 10', I would not think it optimal to set focus at 9' with the knowlege that 'f/8 DOF covers it just fine'. So why apply that line of thought in the darkroom, if that previous sentiment (about focus accuracy on flat art) applies to your thinking while shooting?! That would seem to be inconsistent.
It may be true 'The eye will never know the difference', but in such a case we are knowingly accepting imperfect blur circles as a substitute for perfectly reproduced points of light. The print is inherently less sharp than it could be.
About striving for excellence (not 'perfection') in what we do in photography....
So why not use that same thinking in the darkroom? If you have a piece of photo paper in the easel to make it easier to frame the projection, one merely needs to put the grain focuser on top of the paper, and then remove both after verification of focus. No added effort because the paper is already there, it is merely a question of WHEN the paper is removed, so one does not need to be OCD about focus accuracy.
- Some folks obsess about not using filters when shooting because the photo is 'not as sharp as it could be'.
- Some folks obsess about AF calibration for their camera and each lens because the photo is 'not as sharp as it could be'.
- Some folks will not use a teleconvertor on a long lens because the photo is 'not as sharp as it could be'.
- Some folks always mount the camera on a tripod because the photo is otherwise 'not as sharp as it could be'.
- Many folks use the magnifier in the waist level finder of medium format cameras and most use magnifiers on the large format focusing screen, to improve upon their focus accuracy,
- Most folks use the focus aid in the center of the 135 SLR viewfinder rather than merely relying upon the ground glass area because the photo would be 'not as sharp as it could be'.
- When the exposure is somewhat long, most use mirror lockup, because otherwise the photo is 'not as sharp as it could be'
You already are using a grain focuser...why did you purchase one, if 'good enough' focus is all you want?! You could have saved yourself that expense, and the bother of using it to focus. And why care for it and not simply throw it around, if its accuracy is 'it does not really matter, I cannot see the difference'.
There is apparent inconsistency of thought seen in some of the responses...that, or there seem to be a lot of photographers who settle for 'good enough' in all their methods throughout photography?
It is not being 'dogmatic', it is merely consistency of approach.
I did not intend to suggest that people who are conscientious don’t make mistakes from time to time.I can say that if you are going to take two shots of something important to get it right, it makes sense to go through each setting independently instead of just firing twice.
How I missed the focus of the photographer couple so badly at the wedding I will never know. I took two out of focus shots of them.
Maybe I did better in another roll but I sure can mess up the basics.
I did not intend to suggest that people who are conscientious don’t make mistakes from time to time.
And time is always well spent in coming to an understanding of the limits inherent in the precision of the equipment and techniques we rely upon.Time would be better spent making sure everything is in alignment, including the easel.
sharpness is poorly defined and overrated.
I might take issue with the suggestion that someone who rests his grain focuser on a sheet of enlarging paper when making a print is likely to be the type of photographer who does not exercise very moderate and reasonable levels of care and precision in other areas of the process. I would have come to the opposite conclusion. Of course, I am not an expert on human behavior.
I've found it to be a warning flag of someone having taken too many confidently asserted myths at face value without meaningful or adequate testing - let alone any realistic consideration of what bits of the process really matter.
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