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Jmarmck
17-Dec-2014, 08:47
Is this true?

"Focusing at infinity causes the nearest acceptably sharp objects to correspond with the hyperfocal distance."

Sorry for amateur question.

Dan Fromm
17-Dec-2014, 10:20
Its sort of the other way 'round. Focusing at the hyperfocal distance makes everything from half the hyperfocal distance to infinity acceptably sharp.

The key here is "acceptably sharp." This depends on the photographer's preferences and on how much the negative is to be enlarged to make the final print.

Jmarmck
17-Dec-2014, 11:11
I was wondering if this was a method for finding the hyperfocal point. So for maximum sharpness the focus point should be hyperfocal point + 1 (whatever the units of measure is). Right?

ic-racer
17-Dec-2014, 11:49
Focusing at infinity causes the farthest away objects to be rendered as sharp as possible. Try it you may like it. Since those far-away objects will be the smallest and hardest to identify, maximum resolution is good. Closer objects will be progressively blurrier, but can still be identified due to their progressively larger size.

If there is no important part of the scene in the distance, the focusing method of Hansma works well. In my experience, the pre-printed hyperfocal charts work well only with contact printing. Since I enlarge my negatives, I can't follow the numbers in those charts.

Further discussion on the subject is here:

djdister
17-Dec-2014, 11:57
I was wondering if this was a method for finding the hyperfocal point. So for maximum sharpness the focus point should be hyperfocal point + 1 (whatever the units of measure is). Right?

Of course there is, and it involves math... (or get a hyperfocal calculator app or table)
126772

Lenny Eiger
17-Dec-2014, 12:57
I will add that having made hyperfocal calculations in some circumstances, I was surprised to find that the images were in fact, not as sharp as I expected. I think it was some Rodenstock device I was using.

My experience was that the device's conclusions were just a little bit off. So now I still focus a third of the way in and close down to get full depth of field. It works for me.

Lenny

Jmarmck
17-Dec-2014, 13:18
After reading the posts on Hamsa and a bit on diffraction, I can see that hyper focusing nor the Hamsa method is a cure all. As noted in some of the posts about Hamsa it really is best to use infinity with scenic shots and watch the foreground. If the later becomes an issue then use some degree of hyper focusing may be necessary if diffraction becomes an issue. For close or macro work I have been focusing on some point and checking DOF for coverage. If the apertures get too small then a decision has to be made.

Thanks folks.

Jim Jones
17-Dec-2014, 19:13
Is this true?

"Focusing at infinity causes the nearest acceptably sharp objects to correspond with the hyperfocal distance."

Sorry for amateur question.

Yes, it's true. However, determining the hyperfocal distance and acceptable sharpness is complex. There are charts, computer programs, DOF scales, and other solutions. Unfortunately, they are all based on what someone else considers acceptable sharpness. As for hyperfocal distance, for fairly sharp prints it might be about 2000 times the apparent diameter of the lens' iris as viewed through the front elements. That figure of 2000 can vary widely, depending on final image size, subject matter, and most of all, photographer's definition of sharpness. Most charts, computer programs, and DOF scales are optimistic. If you want to study the subject of DOF in depth, go to http://www.trenholm.org/hmmerk/HMArtls.html and follow those links.

Dan Fromm
18-Dec-2014, 04:52
Jim, I just checked my DoF calculator (mine = I wrote it). It strongly disagrees with you. You can download it from http://1drv.ms/1Ai54SN . Please show me yours.

I wrote that spreadsheet for a discussion here with Helen Bach, whom I salute in passing. She and I were having trouble communicating so I gave her my arithmetic.

William Whitaker
18-Dec-2014, 08:23
This is why they put a ground glass on cameras.

Jim Jones
18-Dec-2014, 18:44
Jim, I just checked my DoF calculator (mine = I wrote it). It strongly disagrees with you. You can download it from http://1drv.ms/1Ai54SN . Please show me yours. . . .

Oops, when I said the hyperfocal distance was about 2000 times the entrance pupil, I neglected the critical element of the image being viewed in correct perspective. Corrections for deviations of viewing perspective can be done mentally in the field with basic math. Your spreadsheet applies to the special condition of constant magnification. I change lenses more to change the field of view than to change the subject distance for constant magnification. As for the math used to derive the formula I use, it was done decades ago with pencil and probably a slide rule, although by then I might have had a new and amazing five function digital Heathkit calculator that cost only \$128, and had to be wired and assembled from the individual components. The math was merely a step in understanding practical optics. Once there, the math could be forgotten, and was. Kingslake in Lenses in Photography gives the formula for hyperfocal distance as 1000 d = h where d is the entrance pupil and h is the hyperfocal distance. This seems too lax for modern film and printing, and too forgiving for Facebook selfies.

Dan Fromm
18-Dec-2014, 19:29
Jim, look at the second tab.

Jim Jones
19-Dec-2014, 10:01
Jim, look at the second tab.

For someone who was a computer maintainer from 1956 to 1959, I hate to admit being almost totally ignorant of spreadsheets and most other modern programs. A quick study of spreadsheets this morning wasn't enlightening to an aging mind. It's back to the copy of Kingslake sadly tattered from 60 years of use.

Dan Fromm
19-Dec-2014, 10:26
Jim, I too have seen ferrite cores. But hardware has little to do with software.

You really should learn to use modern tools, they're useful. And I say this even though my best unpublished paper in comp sci's title is "Spreadsheet Languages Considered Harmful." For context, see http://xkcd.com/292/

Emmanuel BIGLER
19-Dec-2014, 10:52
I hate to admit being almost totally ignorant of spreadsheets and most other modern programs.

Same for me. However some day I had to deliver our student's results after their exams under the form of a spreadsheet file.
Since this day I've discovered how to tweak with students' marks in terms of expected average, standard deviation, and number of students who eventually fail ;-)

And as far as DOF calculations are concerned, having learnt FORTRAN with punched cards, even a spreadsheet in the style onf the 1990's is too modern for me, I prefer an analogue do-it-yourself slide rule of this kind. (http://www.cjoint.com/14dc/DLts6eRbIH2_regle-pdc-5p6-150mm-87mu.pdf)

Drew Wiley
19-Dec-2014, 12:09
As a formally trained commercial photographer, my brother was addicted to those hyperfocal scales on typical MF lenses. I ignore the entire subject and simply
evaluate the problem with my eyes using the GG loupe. What features in the scene do I want in exact focus, what will print acceptably stopped down (just
do it and look at the effect thru the loupe!), and what might I want deliberately out of focus. This is esp easy on the big GG of the 8x10. But I pretty much know
what to expect just from experience with given lenses anyway. Maybe once on the last trip when I didn't have enough time to set up the view camera due to rapidly changing light, I did use the hyperfocal formula for a particular 6x7 shot, and in the print it was obviously a successful strategy.

Jim Jones
19-Dec-2014, 20:58
Dan, JK flip flops, not ferrite cores, were used in that computer in the 1950s. It was built with Univac I technology, although bigger and slower. It had hardwired components and lots of vacuum tubes. I wasn't familiar with ferrite cores until 10 years later.

Drew, a fine ground glass screen and strong loupe is certainly the best way to check DOF and focus. It would have been awfully inconvenient, although not quite impossible, when using Leica rangefinder cameras for many years. Most SLR viewfinders don't have enough magnification. DOF scales were often good enough, but not for occasional demanding photography. I wrestled with those optical formulas to find out why some photos displayed insufficient DOF.