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06-28-2011, 07:18 AM   #46
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QuoteOriginally posted by RioRico Quote
[... I could barely see thru my K20D's VF, let alone the LCD screen. So I stopped-down to f/11, and prefocused to 15m for DOF from 5m to infinity, and just worked it as a P&S. Got nice sharp pictures, you betcha, of mountaintop scenes, of the Front Range extending from Wyoming to New Mexico
Ah for the days when all lenses had a DoF scale on the barrel! I'd forgotten until I read this that I used to carry my old Praktica 'pre-focussed' so that at f11 infinity was just sharp - it meant it was ready to shoot for most distances.

My EOS 300 had a feature which was quite good when it worked - form memory you showed it two points you wanted to be in focus and it selected an appropriate aperture, if it could.

There is very little in the way of DoF information on a modern camera with a modern lens. APS-C viewfinders aren't as good for it as the larger ones in 35mm.

06-28-2011, 07:28 AM   #47
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All my lenses have and for sure all my manual focus lenses have. Just set the hyper focal distance and use the cam as point&shoot.

Personally i have nothing with CIF, it is as reliable as normal AF.
06-29-2011, 02:50 PM   #48
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QuoteOriginally posted by RioRico Quote
[B] So I stopped-down to f/11, and prefocused to 15m for DOF from 5m to infinity, and just worked it as a P&S.
OK, I'm going to show my ignorance for a moment. I understand why you stopped down to f/11. I'm assuming you knew/guessed/preferred to prefocus to 15m. Right? Did this basically come from "experience"? Am I making sense?
06-29-2011, 03:40 PM   #49
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Here is an M50/1.7, set to f11. Look at the scale above the aperture ring, with f numbers on either side of the diamond. The focus ring is set so that the lefthand mark for f11 (third stop from left) is at infinity more or less. The corresponding f11 mark on the right is between 5 and 3 meters.

This DOF scale might not be perfect for APS-C. I don't care about the details of the argument to remember why. If the depth of field started and stopped exactly on those marks, if the scale was not a gross approximation anyway, if the lens was in decent repair and if I could accurately estimate distances by eye with no error, it might be relevant. But (bit of a rant here) anyone who needs that kind of accuracy should consider not focusing with this method.




06-29-2011, 07:12 PM - 1 Like   #50
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QuoteOriginally posted by cardinal43 Quote
OK, I'm going to show my ignorance for a moment. I understand why you stopped down to f/11. I'm assuming you knew/guessed/preferred to prefocus to 15m. Right? Did this basically come from "experience"? Am I making sense?
Dave's picture shows it. Here's how I work it. I'll use my favorite example, a Tokina 21/3.8. That's easy, it's in my hand, it's today's Lens Of The Day.

Suppose I want to make sure I have deep DOF extending to infinity. I set the aperture to f/11. If I was using a 135/FF camera like a Spotmatic, I would set the focus so the infinity mark is at one of the f/11 marks on the lens. The focus mark now points to 1.2m / 4ft. The other f/11 mark is at just over 0.6m / 2ft. So the prefocus aka hyperfocus is 1.2m, and DOF is from 62cm to infinity.

But DOF is different on my K20D and all other APS-C dSLRs, by about 1 f-stop. And I'm paranoid, so I like to leave an extra margin -- I adjust the focus by a bit over 1 f-stop. With the lens still set to f/11, I'll set the infinity mark *inside* the f/8 mark. The focus mark is at 2m / 7ft and the other f/8 mark is just below 1m, just over 3ft. So the prefocus / hyperfocus is 2m and DOF is 1m to infinity.

With Dave's picture, the aperture is f/11 and prefocus is at 8m / 25ft. On a Spotty, you'd read the DOF between the f/11 marks: 4m / 12ft to infinity. On a Kx or K7 or whatever, read the DOF from inside the f/8 marks: about 15ft to somewhere closer than infinity.

On the mountain-climbing drive I mentioned before, I used an old Zeiss 50mm lens. Aperture at f/11. Infinity mark just below f/8; that puts the prefocus to 8ft. The other f/8 mark is at 4ft. So I had clear DOF from 4ft to infinity. No visual focusing needed. So easy! Then I saw marmots by the road -- gotta get pictures! I switched to an old Enna 100mm. Aperture at f/16; f/11 mark at 15ft; other f/11 mark at 8ft; prefocus at 10ft. So my DOF zone was 8-15ft, just right for shooting portraits of the fat rodents.

MOUNTAINEERS' TIP: Keep your eyes peeled for piles of marmot scat. Marmots like to have scenic views when they dump. Marmot latrines often have the best vistas. This is true in the Sierra Nevadas and the Rockies, I can attest.
06-30-2011, 09:38 AM   #51
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@ Just1MoreDave & RioRico:

Thanks for your detailed explanations. This forum is always a learning experience.
06-30-2011, 10:33 AM   #52
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QuoteOriginally posted by cardinal43 Quote
@ Just1MoreDave & RioRico:

Thanks for your detailed explanations. This forum is always a learning experience.
Although he is perhaps the most annoying person in the world of photography, Ken Rockwell has perhaps the best rundown I have ever read on this topic:

How to Select the Sharpest Aperture

Marmot scat, indeed!
06-30-2011, 11:57 AM   #53
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Ken is the most annoying? Gosh, and I try so hard...

Marmot scat indeed. Try it and see.

07-04-2011, 08:36 PM   #54
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i think the issue with appearing sharp on a smaller screen is natural. i read some article about it that stated (which i guess is pretty obvious if you think about it) that depth of field lessens the bigger your screen is. there is no real "sharp". it is just our brains interpretation of "sharp enough" and sorting that as sharp, fooling us (circle of confusion). when you make a pic/print bigger the light dots made by the aperture becomes bigger and therefore becomes visible to our eyes and we percieve it as unsharpness and lessening depth of field. sorry if i'm a bit unfocused (haha) it's 5.30 in the morning and i've been up all night (work). more to the subject i find focusing pretty easy but it's stupid they don't just put a focus screen as default. especially in pentax cams which are known for backwards compability (using manual focus). I guess it could boil down to how good vision you have. mine is not perfect but i dont use spectacles and i can spot pretty small differences in sharpness. perhaps you just adjust the diopter in the camera or get new glasses/check your vision. i guess manual focus is for the young/people with o.k. eyesight or people with cams with focus screens. hope i'm not all bullshit but im pretty tired
07-06-2011, 06:19 AM   #55
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I got to play around with the Vivitar 500mm non-mirror lens last weekend. Once I remembered to green-button the metering, the focus confirmation worked. Trying to brace that behemoth on a fence post was not optimal, and my tripod is inadequate. I did manage to get a few nice images - most of which I could have used another lens and just walked close to the subject, but that wasn't the point of the experiments.

Here's a shot, just a crop from the jpeg with no PP at all. This is the best shot of the day, too.

https://www.pentaxforums.com/forums/members/16769-ter-or/albums/3440-vivitar-500mm-shots/picture27403.html
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