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06-13-2019, 07:27 AM   #1
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K-1 Automatically stops down my Pentax-a 50mm 1.4 in live view.

It does this when there are bright conditions. The brighter it is the further is the further it stops down. Even with the aperture (on body) set to 1.4. It doesn't do this when I set aperture manually with the aperture ring. Is there anyway I can disable this, since it makes it harder to get critical focus right with a wide open aperture.

06-13-2019, 07:29 AM   #2
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What mode are you in?
06-13-2019, 07:33 AM   #3
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Yeah, they all do that in live view to protect the sensor. If it is the same as the earlier bodies I have, if you magnify for focusing it will open up. I think you can also use the optical preview feature (you'd have to hold it open while focusing which might be tricky).
06-13-2019, 07:37 AM   #4
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QuoteOriginally posted by D1N0 Quote
Is there anyway I can disable this, since it makes it harder to get critical focus right with a wide open aperture.
DoF preview in LV mode with change the aperture, and you can even use it in combination with magnification for focusing with the lens stopped down to the aperture that will be used for the actual exposure.

---------- Post added 13-06-19 at 16:43 ----------

QuoteOriginally posted by vonBaloney Quote
Yeah, they all do that in live view to protect the sensor.
I don't know why LV does adjust the lens aperture in LV mode, I just assumed that the aperture is adjusted based in light and the more limited range of exposure times in video mode (live view is a kind of video mode).

06-13-2019, 07:47 AM   #5
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Sometimes the camera is smarter than you in that it understands the technical problems faced by the camera and deals with them. It's hard to understand folks always thinking they are smarter than the Pentax engineers, and have thought of everything. These are not film cameras. The mechanics are well beyond, the simple kinds of understandings that worked when shooting film.
06-13-2019, 07:51 AM   #6
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At f/1.4 and ISO 100, a sunny scene requires a shutter speed faster than the K-1's maximum speed of 1/8000 sec. Thus the camera must either stop-down the lens or over-expose the scene. You could try playing with the Exposure Compensation value to tell the camera to over-expose the scene and see if that helps.
06-13-2019, 07:53 AM   #7
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QuoteOriginally posted by biz-engineer Quote
I don't know why LV does adjust the lens aperture in LV mode, I just assumed that the aperture is adjusted based in light and the more limited range of exposure times in video mode (live view is a kind of video mode).
Pretty sure it is for heat protection because the sensor is always on in LV. Bright light = more heat. It is annoying though for fast manual lenses.
06-13-2019, 08:04 AM   #8
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It seems to track exposure. If I set the aperture manually (with an A lens using the camera controls) and have a shutter speed that would result in underexposure with ambient light, live view is really dark... and the lens is stopped down...

This is a pain when using flash indoors...

-Eric

06-13-2019, 08:18 AM   #9
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QuoteOriginally posted by photoptimist Quote
At f/1.4 and ISO 100, a sunny scene requires a shutter speed faster than the K-1's maximum speed of 1/8000 sec. Thus the camera must either stop-down the lens or over-expose the scene.
I've tried that op it does stop down way before I reach 1/8000th. In magnification it stops back again, so that seems to solve the problem. Focus peaking in normal view will be affected by it though. I have to use the live preview I found. It doesn't show the behavior with all manual lenses, That's probably why I hadn't noticed it before. (of course it couldn't stop down m42, but M lenses could be).
06-13-2019, 08:20 AM   #10
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Possibly the K-1 is a little smarter about it? This only bugs me on the K-01 where LV is the only choice -- otherwise I'm usually using the viewfinder (or an old lens that it can't stop down). On that body it doesn't matter what the exposure settings are -- if it is bright, it stops it down period. For autofocus lenses, it opens up it while it is focusing, but for manual lenses you have to use magnification focus assist and then it will stay open as long as that is engaged.
06-13-2019, 09:47 AM   #11
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As noted above, "protective" stop-down in bright light is a long-time "feature" of live view on Pentax dSLRs and should be taken into account when doing fine focus in that mode. It can be defeated by using the DOF preview button (yes...cumbersome) or using the lens aperture ring if present.

Edit: ...or using magnification for fine focus. I had forgotten this last despite using the feature frequently.


Steve

Last edited by stevebrot; 06-13-2019 at 10:33 AM.
06-13-2019, 09:50 AM   #12
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QuoteOriginally posted by TwoUptons Quote
This is a pain when using flash indoors...
:-) not if you understand how the firmware works. It's not meant to use a flash, it's meant to simulate exposure without flash. I discovered the subtleties of what the firmware is doing and found it to be quite smart but nothing of this is written in the manual.
06-13-2019, 10:27 AM   #13
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QuoteOriginally posted by TwoUptons Quote
It seems to track exposure. If I set the aperture manually (with an A lens using the camera controls) and have a shutter speed that would result in underexposure with ambient light, live view is really dark... and the lens is stopped down...

This is a pain when using flash indoors...

-Eric
That is a different live view feature; the generic term for it is "exposure simulation" where the display darkens/lightens for intentional under/over exposure. Yes, this may cause problems when attempting to balance flash using exposure compensation. The display may be too dark for framing. In that case, the optical viewfinder might by the better option. If using a K01...things are not as happy.


Steve
06-13-2019, 10:32 AM   #14
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QuoteOriginally posted by D1N0 Quote
In magnification it stops back again, so that seems to solve the problem.
This trick works on my K-3. Do you know if all models follow this behavior for magnification?


Steve
06-13-2019, 10:34 AM - 1 Like   #15
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Do we need a separate category named "I don't know what I am doing but somehow its K-1s fault..." for these kind of posts? There is atleast one that I usually see floating on the front page that can belong to this category. Reading those posts It almost sounds like Pentax is a start up company and came out with their first full frame DSLR product not know what they must be doing.

No offense to the OP but a thought in general.

May be Pentax should not lower the price of K-1 so much so that it becomes accessible to people who never have had a SLR/DSLR before needless to say with no prior experience to any SLRs operations/function.
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