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05-03-2011, 04:36 AM   #1
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DOF Scales on DA lenses

All of my manual lenses have DOF scales.

My DA 18-55 and DA 55-200 do not however.

I see that some, but not all, DA primes have DOF scales

Why is that? Was there a technical reason for pentax not to print out a DOF scale on some of their lenses? Are DOF scales not needed as much anymore because of auto-focussing?

I just read up on how they work and I am glad I know them now. But I wonder if, in todays terms, they are similar to slide scales? I taught myself how to use them, but they are impractical today.

05-03-2011, 04:52 AM   #2
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I can't tell you why pentax leaves them off of some lenses. I think they still have use but people spend more time staring at rear screens now days rather than looking through the viewfinder. It may have just been one of those 'executive' decisions to leave them off of the more low budget ended lenses.

05-03-2011, 05:23 AM   #3
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Manual focusing 'one-touch' zooms sometimes had DOF scales although I doubt they were that accurate. I can't see how you would put scales on a two-touch zoom - which focal length would you use to calculate them?
All the Pentax primes listed on my signature have DOF scales, but the focusing throw on most AF lenses is so short that the scales are mostly useless. The scale on the 14mm is just about useable (allowing for the fact that its normal to use one or two stops less than suggested by DOF markings).
Now the scales on the standard and wide-anglel enses for my Bronica 645RF, where the throw is over 180 degrees (this is a guess as I don't have them to hand) really are useful...
05-03-2011, 07:23 AM   #4
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QuoteOriginally posted by Capslock118 Quote
I just read up on how they work and I am glad I know them now. But I wonder if, in todays terms, they are similar to slide scales? I taught myself how to use them, but they are impractical today
depends on how big you're going to print your photos really. Anything smaller than 8X10 the DOF scales work quite well but for anything bigger than that compromises are involved.

05-03-2011, 08:10 AM   #5
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QuoteQuote:
depends on how big you're going to print your photos really. Anything smaller than 8X10 the DOF scales work quite well but for anything bigger than that compromises are involved.
camera is a k100d and from what i've read, i don't really want to push larger than 8x10 on a 6mp camera anyways.

I've just been using my manual primes recently to get to know them better and have a better eye for focusing manually.

finding out how the DOF scales work has been a real treat during play time.
05-03-2011, 09:19 PM   #6
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As said, impossible to make for two ring zooms. Be glad you have those lenses and not the L versions (DA-L 18-55, DA-L 50-200, DA(L)35/2.4. They don't even have a distance scale which makes life even more impossible.
05-03-2011, 10:31 PM   #7
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DOF scales are handy for hyperfocal, but I recently found out how easy it was to calculate hyperfocal. On our crop sensors, it's essentially:

(focal length)^22 * 50 / (f-number).

Don't forget the units, your focal length is in mm but you typically want to convert it to meters for setting hyperfocal.
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