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05-21-2014, 09:33 AM   #1
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K-3, Pentax-A lenses, Program Line

Moderators...please feel free to close/delete this thread if this behavior has been noted in the past.

I was just fiddling with my K-3 mounted to the Pentax-A 50/1.7 and noticed that the program line behaves differently with lenses lacking the data contact depending on the program-line mode. To reproduce:
  • Mount a Pentax-A lens to the camera
  • Set the program line to optimize DOF
  • Set the exposure mode dial to "P" and note that the aperture is set to f/11
  • Point the camera at subjects with various brightness and note that the aperture stays at f/11
  • Use the rear e-dial to change the aperture and note that the shutter speed changes appropriately
  • Press the green button to reset to program line and note that the aperture returns to f/11
  • Change the program line to either "Auto" or "Normal" and note that the aperture floats as with AF lenses
Yep, P-mode essentially behaves as Av mode except when program line is set to "Auto" or "Normal". To make things even more interesting, change the mode dial to "M" and note that the aperture is similarly "pinned" when the green button is pushed, but to a different value than when in P-mode.

Edit:
I did some additional testing at higher ISOs and was able to coerce the camera to use apertures narrower than f/11, with the wide DOF program line, but not wider. Similarly, I was able to get narrower than f/1.7 with the narrow DOF program line. The numbers, however, were significantly different than with the DA 50/1.8 and probably not optimal for general shooting.
/Edit

As a result, I suggest that users who frequently mount vintage glass avoid use of be aware of the behavior of the various optional program lines.

Edit:
I have posted the reply from Ricoh/Pentax support later in this thread. For those who want to cut to the chase...
https://www.pentaxforums.com/forums/172-pentax-k-3/262923-k-3-pentax-lenses-p...ml#post2823398
/Edit


Steve

BTW...I am running firmware v1.03


Last edited by stevebrot; 05-22-2014 at 01:26 PM.
05-21-2014, 11:05 AM   #2
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My K-5 II defaults to AV if I mount a m42 lens in anything other than M. But I don't know the behaviour with A lenses.
05-21-2014, 11:13 AM   #3
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QuoteOriginally posted by Giklab Quote
My K-5 II defaults to AV if I mount a m42 lens in anything other than M. But I don't know the behaviour with A lenses.
That is the expected behavior. What I reported above is a deviation from the camera documentation and the general advice given by users on this site. All exposure modes should be available and work properly with lenses having the KA mount.
05-21-2014, 11:53 AM   #4
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Steve: On page Manual 71: You can change the default behavior of the Modes and the behavior of the e-dials in each mode to suit your needs. Do you suppose the camera is programmed to f/11 default aperture for A50/1.7 in P >> DoF because Pentax engineers believe that is the optimal DoF aperture? Do Sv and/or ISO float when light intensity changes?

I'm going to give this a workout with a A50/1.4 this evening - just for grins.

05-21-2014, 01:10 PM   #5
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QuoteOriginally posted by monochrome Quote
Do you suppose the camera is programmed to f/11 default aperture for A50/1.7 in P >> DoF because Pentax engineers believe that is the optimal DoF aperture?
I did a little more fiddling and discovered that if I bump the ISO to a higher value, I can get an aperture of narrower than f/11, but not wider, so my assertion that it is similar to Av mode is not quite accurate. What it appears to be doing is defaulting to a VERY conservative line for each of the specialty program lines when the data pin is not detected. This feature works fine on my K10D but the current behavior is hardly optimal.

I have notified Ricoh/Pentax and am curious as to their response.

As for the manual...my settings for P mode are the default.


Steve

Last edited by stevebrot; 05-21-2014 at 01:42 PM.
05-21-2014, 02:00 PM   #6
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Steve, I just tried to replicate your issue with my K3 and my A 50mm f/1.7 and I cannot replicate your problem. No matter what program mode I use, aperture responds as it should.
I also tried pretty much every setting combination imaginable and the exposure settings are always identical (or too close to bother) with the DA50mm f/1.8 or the A50.
I also/also tried with my only other "A" lens (tak 28mm f/2.8) and with that lens too, everything works as it should.
05-21-2014, 05:09 PM   #7
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QuoteOriginally posted by fgaudet Quote
Steve, I just tried to replicate your issue with my K3 and my A 50mm f/1.7 and I cannot replicate your problem. No matter what program mode I use, aperture responds as it should.
I also tried pretty much every setting combination imaginable and the exposure settings are always identical (or too close to bother) with the DA50mm f/1.8 or the A50.
I also/also tried with my only other "A" lens (tak 28mm f/2.8) and with that lens too, everything works as it should.
Very strange. Were you using program lines other than "auto" or "normal"? What ISO? What firmware version?

Perhaps I have a defective camera. My other "A" lens is the Adaptal-2 KA mount and it behaves the same as my A 50/1.7.


Steve

Last edited by stevebrot; 05-21-2014 at 05:31 PM.
05-21-2014, 05:35 PM   #8
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QuoteOriginally posted by stevebrot Quote
Very strange. Were you using program lines other than "auto" or "normal"? What ISO? What firmware version?
Sorry, I meant to put more details but I got sidetracked... I tried all 6 different program lines in a few different places to "force" the camera to change settings (outside, inside, light, dark). If there is one thing to say is that using the DOF line is almost too keen on wide aperture, it had to be very bright for the camera to select aperture smaller than f/1.7 (or 1.8), more so than on the K5. All done using auto WB and auto ISO from 100 to 1600.

Camera is running FW 1.03 and my overall settings are pretty basic (no highlight/shadow/CA/distortion correction, no filter, no nothing). With body only and with a MacGyvered BG04. With the battery that came with the K3 (3 recharge cycles so far) and a 3 yo one and with a chinese one all at various charge level.

05-21-2014, 05:46 PM   #9
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QuoteOriginally posted by fgaudet Quote
using the DOF line
Which DOF line? There are two, large and small. Your general setup is similar to mine except that I ditched auto-ISO almost immediately after I got the camera. To illustrate what I am seeing at ISO 400 using the large DOF program line (biased to narrower apertures):

DA 50/1.8: 1/80s @ f/5.6
A 50/1.7: 1/15s @ f/11

I would say that the camera is using a different program line, eh? The exposures are essentially equivalent (similar EV with the A 50 metering providing the better histogram), but the settings are obviously derived from a different algorithm.


Steve

Last edited by stevebrot; 05-21-2014 at 05:57 PM.
05-21-2014, 06:01 PM   #10
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QuoteOriginally posted by stevebrot Quote
Which DOF line?
The "portrait" / shallow DOF one.
05-21-2014, 07:45 PM   #11
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Using an A50/1.4
Program Mode
Large DoF setting (Body/Mountain)
Default progression curve (Medium or Middle)
e-dials set Av front Tv rear (this is a critical choice)
ISO Auto 100-6400
GB returns camera to Program Line.
Aperture is f/11
ISO is 2000
EV Comp is centered
Changing light intensity changes shutter speed and nothing else
Changing Av with e-dial
Camera immediately switches to Av HYPER (Hyper Program) As displayed in upper left of LCD
As I roll the e-dial to change aperture, shutter speed [EDIT: ISO stays at 2000 and ISO] float to maintain metered exposure
Changing Sv with e-dial
Camera immediately switches to Sv HYPER (Hyper Program) As displayed in upper left of LCD
As I roll the e-dial to change shutter speed, aperture [EDIT: ISO stays at 2000 and ISO] float to maintain metered exposure
IIRC this is normal behavior.

I can confirm with K10D and Edit later if that will be helpful

Last edited by monochrome; 05-22-2014 at 06:13 AM.
05-21-2014, 08:25 PM   #12
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QuoteOriginally posted by monochrome Quote
Aperture is f/11
QuoteOriginally posted by monochrome Quote
Changing light intensity changes shutter speed and nothing else
This is the abnormal part. It will go no lower (wider) than f/11 though I was able to get it to go narrower at high ISOs. Do the same with an autofocus lens and see the difference. With an AF lens it will apply a program line that provides 1 or 2 stops additional DOF than the "normal" program.

QuoteOriginally posted by monochrome Quote
IIRC this is normal behavior.
Yes, the hyper-program feature works as expected. What does not work as expected is the program line.


Steve

---------- Post added 05-21-14 at 08:27 PM ----------

QuoteOriginally posted by monochrome Quote
e-dials set Av front Tv rear (this is a critical choice)
Default (my setting) is the opposite of this, but it should make no difference.

I have been looking more closely at the M-mode behavior. It appears to be different than how P-mode works in regards to "A" lenses and program line.


Steve

Last edited by stevebrot; 05-21-2014 at 08:41 PM.
05-21-2014, 08:39 PM   #13
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ISO can be adjusted upward using the ISO button in front of the top LCD, which then allows a wider aperture. If I am correct that is the big change - you must manually adjust the ISO to allow P Mode Green Button to set a wider aperture.
05-21-2014, 08:56 PM   #14
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QuoteOriginally posted by monochrome Quote
ISO can be adjusted upward using the ISO button in front of the top LCD, which then allows a wider aperture.
Narrower aperture...been there, tried that F/11 is the widest it would go and then only at ISO 100.


Steve
05-22-2014, 06:18 AM   #15
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QuoteOriginally posted by stevebrot Quote
Narrower aperture...been there, tried that F/11 is the widest it would go and then only at ISO 100.


Steve
Apparently Program Line is different but I think I unwittingly have used HyperP (or M with 'K' lenses) using MF lenses. K10D to K3 has been a big leap for me, as well. I didn't have the K7/K5 steps and the K-01 uses a slightly different menu and function set.

Last edited by monochrome; 05-22-2014 at 07:37 AM.
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