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03-05-2016, 11:58 PM - 1 Like   #31
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QuoteOriginally posted by jatrax Quote
The one question I have never had answered was how using a crop sensor affected this.
1) On a FF lens such as a Pentax-A can the marks be used as is or do we need to add a stop? I believe Rio Rico felt that the marks as is were for FF and had to be adjusted for APS-C. Others disagreed.

2) On DA lenses such as the 15mm and the 21mm were the marks designed for APS-C and thus should be used as is or do they also need adjusted?
Lens DOF scales are appropriate for the intended format. The numbers for FF are quite different than for APS-C

The whole matter of the DOF scales is sort of strange in that they vary across makers for a particular focal length. Those on my Russian and former Soviet glass are very optimistic while the Japanese lenses are less so but still vary between brands. I guess tomorrow I could gather several examples together for a group shoot

If one must be precise, I suggest using a DOF phone app and place the focus scale at the appropriate distance for hyperfocal at the desired aperture.

Examples for APS-C using DoF Android app:
DA 15 at f/8 is hyperfocal at 4.7'
DA 21 at f/8 is hyperfocal at 9.1'
DA 35 at f/8 is hyperfocal at 25.2'
Examples for FF using the DoF Android app:
FA 20 at f/8 is hyperfocal at 5.5'
FA 35 at f/8 is hyperfocal at 16.9'
Steve


Last edited by stevebrot; 03-06-2016 at 12:11 AM.
03-06-2016, 12:49 AM   #32
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QuoteOriginally posted by stevebrot Quote
I guess tomorrow I could gather several examples together for a group shoot
Skip the photos. For three FF 28mm lenses at f/16 set to the hyperfocal, the scales read:

Tamron 28/2.5 (02B):
Hyperfocal = 5'
Near = 2.8'
Vivitar 28/2.8 CF (Komine):
Hyperfocal = 5' (a little over)
Near = 2.9'
S-M-C Takumar 28/3.5:
Hyperfocal = 5'
Near = 2' (!)
Repeating for 35mm at f/16, the scales read:

Pentax-FA 35/2:
Hyperfocal = 7'
Near = ~4'
LZOS Jupitar 12 35/2.8:
Hyperfocal = ~6.2'
Near = ~3.2'
MC W.Rokkor-HG 35/2.8:
Hyperfocal = ~7.5'
Near = 4'
And finally 50mm at f/16:

Pentax-M 50/1.7:
Hyperfocal = 16.4'
Near = 8'
XR Rikenon 50/2
Hyperfocal = 16.4'
Near = ~8.5'
Auto Rikenon 50/1.7
Hyperfocal = ~17'
Near = ~9'
KMZ Jupiter-8 50/2 (LTM)
Hyperfocal = 13.1'
Near = 6.6'

Just a little something to chew on when it is tempting to agonize over focus scales I have done successful zone focus with all of the above.


Steve
03-06-2016, 01:32 AM   #33
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Thanks very much to all the comments. So I gather this is what I will need to do...

Tomorrow I will setup a tripod with a measuring tape to measure the hyperfocal distrance for each lens from the camera to an object. I think I can use my backfence of the house yes?

So if the hyperfocal distance is 1.3m, I will setup the tripod 1.3m away from the fence. The thing I would like to know is...from which point on the camera do I measure from? from the edge of the lens or from the body (if if the body, from whcih part, the flange?)

Also, does it matter if I do this using a K-01 or K-3? Any Pentax APS camera will do the trick yes?

If there are glaring mistakes with my proposed action tomrrow, please do tell.

Thanks again
03-06-2016, 03:58 AM   #34
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QuoteOriginally posted by pathdoc Quote
Last I checked, one third of infinity was still infinity. Do you mean the gauged distance to the far horizon, or have you some more precise measure in mind?
I have found that one of the amazing things about Pentax lenses is that they really do go "To Infinity and Beyond!"

03-06-2016, 07:34 AM   #35
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QuoteOriginally posted by raider Quote
from the edge of the lens or from the body (if if the body, from whcih part, the flange?)
From the camera sensor, which is 45.46mm from the camera mount into the body.
QuoteOriginally posted by raider Quote
Also, does it matter if I do this using a K-01 or K-3? Any Pentax APS camera will do the trick yes?
They might have different circle of confusion and the K-3 has higher resolution. I'd use the K-3, 2 sec timer, ISO 100. And a custom WB for that scene.
03-06-2016, 07:39 AM   #36
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QuoteOriginally posted by Na Horuk Quote
From the camera sensor, which is 45.46mm from the camera mount into the body.

They might have different circle of confusion and the K-3 has higher resolution. I'd use the K-3, 2 sec timer, ISO 100. And a custom WB for that scene.
Thanks Na Horuk. I will try this out tomorrow morning.
03-06-2016, 07:41 AM   #37
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QuoteOriginally posted by stevebrot Quote
And finally 50mm at f/16: Pentax-M 50/1.7: Hyperfocal = 16.4' Near = 8' XR Rikenon 50/2 Hyperfocal = 16.4' Near = ~8.5' Auto Rikenon 50/1.7 Hyperfocal = ~17' Near = ~9' KMZ Jupiter-8 50/2 (LTM) Hyperfocal = 13.1' Near = 6.6'
I want to add some more 50mms at f16: The plastic Miranda 50mm f1.9 has a focus ring going the other way than Pentax M. It has different-looking DoF marks, but @f16 it goes from infinity to appx 8-9ft (very similar in numbers to the M)
Industar 50-2 50mm f3,5 (Soviet Zeiss clone), according to its label, @f16 goes from infinity to appx 5.7 feet (label is in metres, a little over the 1.7m mark). So these are fairly consistent, I guess.
03-06-2016, 08:54 AM   #38
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QuoteOriginally posted by raider Quote
The thing I would like to know is...from which point on the camera do I measure from?
On the side of the prism near the top lcd there is a Φ (greek letter pi) which marks the point you should measure from.

03-06-2016, 11:37 AM   #39
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QuoteOriginally posted by Na Horuk Quote
I want to add some more 50mms at f16: The plastic Miranda 50mm f1.9 has a focus ring going the other way than Pentax M. It has different-looking DoF marks, but @f16 it goes from infinity to appx 8-9ft (very similar in numbers to the M)
Industar 50-2 50mm f3,5 (Soviet Zeiss clone), according to its label, @f16 goes from infinity to appx 5.7 feet (label is in metres, a little over the 1.7m mark). So these are fairly consistent, I guess.
I would have to do some research, but IIRC there were competing early proposals for acceptable circle of confusion. I have wondered at what point the Soviets diverged from the more common standard of 1/30mm for 35mm film.


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03-06-2016, 06:07 PM   #40
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Okay. I did a test using the DA15 this morning.

According to the DOF calculator, at F8, the DA15's hyperfocus distance is 1.42m. So I setup the tripod and measure 1.42m from a brickwall to the pi symbol on the camera.



Then I activate liveview and autofocus on the centre part of the LCD. Then turn off autofocus.
Swivel the tripod to shoot a distant object. focusing ring untouch.

What I get is an image that is not sharp.

If I auto focus on a distant object, the result is a lot better.

What am I doing wrong?
03-06-2016, 06:28 PM   #41
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Note that everything inside 70cm at your settings will be out of focus.

Try the opposite ... focus on something in the extreme distance, and look back at your measuring tape to see how close it gets to you before it's not sharp.
03-06-2016, 09:25 PM   #42
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QuoteOriginally posted by raider Quote
Then I activate liveview and autofocus on the centre part of the LCD. Then turn off autofocus.
Swivel the tripod to shoot a distant object. focusing ring untouch.

What I get is an image that is not sharp.

If I auto focus on a distant object, the result is a lot better.

What am I doing wrong?
Nothing. Make an 8x10" print of the image and view it from 10". You should expect acceptable sharpness from 1.42m to infinity with stuff at 1.42m being somewhat sharper than objects beyond that distance. You should also see acceptable sharpness from about 0.72m to 1.42m.


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03-07-2016, 02:46 AM   #43
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QuoteOriginally posted by raider Quote
What am I doing wrong?
Using the DA15.

Basically you are discovering that antiquated DoF calculators are a waste of time on digital, since they do not take into account the discrete nature of digital photography and the many rescaling steps an image usually goes through from being recorded by the sensor to being viewed on a monitor or printed on a bit of paper.

Decide what sharpness is acceptable to you and use that as a basis for any DoF guess.
03-07-2016, 03:05 AM   #44
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QuoteOriginally posted by kh1234567890 Quote
Using the DA15.
:Lol:
03-07-2016, 12:27 PM   #45
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QuoteOriginally posted by kh1234567890 Quote
Basically you are discovering that antiquated DoF calculators are a waste of time on digital, since they do not take into account the discrete nature of digital photography and the many rescaling steps an image usually goes through from being recorded by the sensor to being viewed on a monitor or printed on a bit of paper.
That is a new one...definitely a new one...



I guess it is like the rescaling steps that happen in the traditional wet darkroom.


Steve
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