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03-20-2022, 06:45 AM   #1
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does Pentax dslr somehow adjust diaphragm on "A" lenses?

Using "A" lenses, do K70 et al somehow adjust more than shutter with some settings? Seems impossible...also seems to be real with my 28 "A" an 50 "A" macro.

03-20-2022, 06:52 AM   #2
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QuoteOriginally posted by janosh Quote
Using "A" lenses, do K70 et al somehow adjust more than shutter with some settings? Seems impossible...also seems to be real with my 28 "A" an 50 "A" macro.
All Pentax-A lenses work in all program and manual modes on all their DSLRs. The aperture is automatically set in programmed and shutter priority modes (P and Tv...also Sv). The only functional difference between A and F/FA lenses is the autofocus.
03-20-2022, 07:05 AM   #3
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QuoteOriginally posted by tonyzoc Quote
All Pentax-A lenses work in all program and manual modes on all their DSLRs. The aperture is automatically set in programmed and shutter priority modes (P and Tv...also Sv). The only functional difference between A and F/FA lenses is the autofocus.

I'm wondering if HDR setting (which produces multiple overlapping/interacting exposures) is doing multiple micro-focus between those multiple HDR exposures. Is that possible?
03-20-2022, 07:20 AM - 2 Likes   #4
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QuoteOriginally posted by janosh Quote
Using "A" lenses, do K70 et al somehow adjust more than shutter with some settings? Seems impossible...also seems to be real with my 28 "A" an 50 "A" macro.
When the aperture ring on a "A" lens is set to the "A" position, the aperture behaves like any more modern lens. It can be set with the e-dial in Manual or Bulb mode or X-SYNC. In Av or TAv mode it is also set with the e-dial and the camera will adjust the shutter speed or ISO accordingly. In Tv or P or AUTO mode the camera will set the aperture required for exposure.

Now if you take the ring off the "A" setting, you lose a lot of functionality. If you set the ring to any actual aperture setting, that aperture will only be used in Manual or Bulb or X-SYNC. In any other of the auto modes the camera reverts to Av mode but at maximum aperture only. So setting the ring to say f8 and the mode to P will give you Av mode at f2.8 on your 50mm Macro.

---------- Post added 03-20-22 at 02:23 PM ----------

QuoteOriginally posted by janosh Quote
I'm wondering if HDR setting (which produces multiple overlapping/interacting exposures) is doing multiple micro-focus between those multiple HDR exposures. Is that possible?
What is the problem you are seeing ?

When the camera combines multiple images for HDR it will use Auto-Align (unless you turn that off) to combine the images. If you are using a slow shutter speed or have things moving in the scene during HDR capture, this can lead to odd images which look like out of focus or double images.


Last edited by pschlute; 03-20-2022 at 07:36 AM.
03-20-2022, 07:37 AM   #5
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QuoteOriginally posted by pschlute Quote
When the aperture ring on a "A" lens is set to the "A" position, the aperture behaves like any more modern lens. It can be set with the e-dial in Manual or Bulb mode or X-SYNC. In Av or TAv mode it is also set with the e-dial and the camera will adjust the shutter speed or ISO accordingly. In Tv or P or AUTO mode the camera will set the aperture required for exposure.

Now if you take the ring off the "A" setting, you lose a lot of functionality. If you set the ring to any actual aperture setting, that aperture will only be used in Manual or Bulb or X-SYNC. In any other of the auto modes the camera reverts to Av mode but at maximum aperture only. So setting the ring to say f8 and the mode to P will give you Av mode at f2.8 on your 50mm Macro.

---------- Post added 03-20-22 at 02:23 PM ----------



What is the problem you are seeing ?

I'm not seeing a "problem." I'm seeing what appears to be remarkable depth of field...wondering if the moments between HDR exposures, which might theoretically result in differing depths of field, arguably be involved. OR am I just enjoying DOF characteristics of these two exceptional "A" lenses, wide open (seems expecially remarkable with 50/2.8 .

---------- Post added 03-20-22 at 07:42 AM ----------

I will compare/contrast those "A" primes with my 18-55 Samsung set to those distances of same setup. Samsung zooms are extraordinary fwiw...wish mine could be adapted to Pentax.
03-20-2022, 09:26 AM   #6
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If I am understanding you right, the HDR setting is where you notice this. With HDR there are 3 exposures combines 1 under, 1at normal and 1 over exposed. The camera can use a combination of shutter speeds and apertures to achieve this. If the aperture changes, so does your depth of field and perceived sharpness in the final HDR combined image
03-20-2022, 09:33 AM   #7
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Thank you all for your patience. I've only been shooting/developing/printing since my mother taught me, almost 70 years ago

---------- Post added 03-20-22 at 09:38 AM ----------

QuoteOriginally posted by garywakeling Quote
If I am understanding you right, the HDR setting is where you notice this. With HDR there are 3 exposures combines 1 under, 1at normal and 1 over exposed. The camera can use a combination of shutter speeds and apertures to achieve this. If the aperture changes, so does your depth of field and perceived sharpness in the final HDR combined image

YES! I do love (prioritize) HDR and YES, it is perceived sharper...though I'm amazed (and remain in doubt) that HDR can make a difference in "perceived sharpness." I will convert some files to B&W via NIK, print them, and see if this HDR/sharpness idea is confirmed in practice (I do more B&W inkjet printing than color). .


Last edited by janosh; 03-20-2022 at 01:57 PM.
03-20-2022, 09:44 AM   #8
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QuoteOriginally posted by janosh Quote
Thank you all for your patience. I've only been shooting/developing/printing since my mother taught me, almost 70 years ago

---------- Post added 03-20-22 at 09:38 AM ----------




YES! I do love (prioritize) HDR and YES, it is perceived sharper...though I'm amazed (and remain in doubt) that HDR can make a difference in "percieved sharpness." I will convert some files to B&W via NIK, print them, and see if this HDR/sharpness idea is confirmed in practice (I do more B&W inkjet printing than color). .
Can you post some jpgs strait out of the camera with Exif intact?

What mode Av, P, M etc are you using for these hdr shots?

As far as I know, if you use the Av mode the camera only adjusts shutter speed (maybe iso too?). Also if shooting with an autofocus lens it might refocus on each shot, but I don’t think it does. It certainly doesn’t do so systematically.

You might want to post the settings (which hdr mode and settings etc.) to help identify things also.

70 years is a long time. I’ve only been doing this for 50.
03-20-2022, 10:59 AM - 2 Likes   #9
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QuoteOriginally posted by janosh Quote
I'm not seeing a "problem." I'm seeing what appears to be remarkable depth of field...wondering if the moments between HDR exposures, which might theoretically result in differing depths of field, arguably be involved. OR am I just enjoying DOF characteristics of these two exceptional "A" lenses, wide open (seems expecially remarkable with 50/2.8 .

---------- Post added 03-20-22 at 07:42 AM ----------

I will compare/contrast those "A" primes with my 18-55 Samsung set to those distances of same setup. Samsung zooms are extraordinary fwiw...wish mine could be adapted to Pentax.
I believe you could be seeing improved contrast, which can seem like more. sharpness and DOF.
03-20-2022, 02:33 PM   #10
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QuoteOriginally posted by janosh:
Thank you all for your patience. I've only been shooting/developing/printing since my mother taught me, almost 70 years ago
Awesome... but I'll bet your Mom never taught you about digital HDR, right?!?

I'm still learning stuff about radio and electronics that I was initially taught as a kid by my Dad... It never ends

QuoteOriginally posted by ramseybuckeye Quote
I believe you could be seeing improved contrast, which can seem like more. sharpness and DOF.
That would be my first thought here, too... Contrast - especially local rather than global contrast - increases perceived sharpness, and it's one of the factors in HDR processing. This could indeed lead to a perception of increased depth-of-field...

Last edited by BigMackCam; 03-20-2022 at 03:05 PM.
03-20-2022, 03:05 PM   #11
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Very interesting insights here.

As to the "A" position, it should be kept in mind that it functions the same way as would a lens on the camera having no aperture ring at all, which these days are most lenses.
03-22-2022, 01:43 AM   #12
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QuoteOriginally posted by UncleVanya Quote
70 years is a long time. I’ve only been doing this for 50.
50 years is a long time. I've only been doing this for 40.
03-22-2022, 05:51 AM - 1 Like   #13
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QuoteOriginally posted by Smolk Quote
50 years is a long time. I've only been doing this for 40.
Lol. I think we qualify as experienced when we can measure in decades the time in the hobby. But truthfully the number of images made, the types of challenges we have tackled, our artistic “vision” give us a unique experience - that’s why I enjoy the forums; I can meet people I’d never encounter in a lifetime of photography and get some of their advice and perspective.
03-22-2022, 10:31 AM - 1 Like   #14
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QuoteOriginally posted by UncleVanya Quote
Lol. I think we qualify as experienced when we can measure in decades the time in the hobby. But truthfully the number of images made, the types of challenges we have tackled, our artistic “vision” give us a unique experience - that’s why I enjoy the forums; I can meet people I’d never encounter in a lifetime of photography and get some of their advice and perspective.
So very true, and we can talk back and forth, country-over to-country, continent-over to-continent! This widens experience even more. 47 years here.
03-22-2022, 02:49 PM   #15
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QuoteOriginally posted by UncleVanya Quote
Lol. I think we qualify as experienced when we can measure in decades the time in the hobby. But truthfully the number of images made, the types of challenges we have tackled, our artistic “vision” give us a unique experience - that’s why I enjoy the forums; I can meet people I’d never encounter in a lifetime of photography and get some of their advice and perspective.
QuoteOriginally posted by mikesbike Quote
So very true, and we can talk back and forth, country-over to-country, continent-over to-continent! This widens experience even more. 47 years here.
Only 14 years or so for me (I was a very late starter) - but I was able to accelerate my learning and experience with the help of you good folks here on PF
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