Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-16-2014, 03:32 PM   #1
Loyal Site Supporter
Mikesul's Avatar

Join Date: Sep 2009
Location: Phoenix, AZ
Posts: 2,655
Odd TAV behavior

I like TAV mode on Pentax cameras a lot. However, recently there has been some odd behavior. Mainly it works as expected: A set to 5.6; S set to 500; ISO floating to get proper exposure. However, yesterday a series of photos came our hugely over exposed using FA 31 on the K3. Other photos with the same settings were just fine - no clear pattern. The EXIF shows ISO 100 was used so that should not have been the problem. When I noticed the behavior I retook one of the shots in A mode (same settings) it came out fine, perhaps slightly underexposed. Any thoughts? Oh yes, exposure compensation was at +03 but it has been there for ages without problems.

11-16-2014, 03:36 PM - 1 Like   #2
Pentaxian
LensBeginner's Avatar

Join Date: Sep 2014
Photos: Albums
Posts: 2,601
Maybe there was way too much light for auto ISO to cope?
If you were fully open and with a low enough shutter speed the camera could have tried hard to keep the exposure under control by lowering the ISO, but couldn't go past 100...

Were there noticeable difference in light between the pictures that came out ok and those who didn't?
I see from your number of posts that you're quite an experienced user, but I wanted to try and point out the obvious nonetheless... we're humans after all!
11-16-2014, 04:03 PM   #3
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,436
Two comments/questions:
  • ISO always "floats" in TAv mode. That is how it works *
  • Did you have the aperture ring on the FA 31 on the "A" position?


Steve

* I generally recommend turning off auto-ISO unless you are a total noob.
11-16-2014, 04:09 PM   #4
Site Supporter
ramseybuckeye's Avatar

Join Date: Apr 2009
Location: Elida, Ohio
Photos: Gallery | Albums
Posts: 8,622
It does sound like it metered to much light, what metering mode were you using? I've had that happen if I accidentally left in in spot mode when it should have been multi.

11-16-2014, 04:14 PM   #5
Pentaxian
aleonx3's Avatar

Join Date: Jul 2007
Location: Brampton, Ontario
Photos: Gallery | Albums
Posts: 3,888
As rameybuckeye has suggested, could it be that the metering mode is accidentally knocked off to spot mode? I have had similar instance before using my k-5IIs.
11-16-2014, 05:30 PM   #6
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,436
QuoteOriginally posted by Mikesul Quote
Oh yes, exposure compensation was at +03 but it has been there for ages without problems.
Hmmm...that is enough to make Caucasian skin appear white as a snowbank and make lighter tones totally clip to full white.


Steve
11-16-2014, 05:33 PM   #7
Loyal Site Supporter
Mikesul's Avatar

Join Date: Sep 2009
Location: Phoenix, AZ
Posts: 2,655
Original Poster
QuoteOriginally posted by stevebrot Quote
Hmmm...that is enough to make Caucasian skin appear white as a snowbank and make lighter tones totally clip to full white.


Steve
Not really, +03 has minimal effect. By the way, I went out again this afternoon to many of the same places with similar TAV settings without a problem (with and without +03). I will look closely at the EXIFs of the bad shots from yesterday to see if I can find some errant setings.
11-16-2014, 07:24 PM   #8
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 9,193
QuoteOriginally posted by Mikesul Quote
The EXIF shows ISO 100 was used so that should not have been the problem.
As LensBeginner pointed out, the use of "ISO 100" could indeed be the clue to the source of your problem.

The K-3 cannot go below ISO 100, so has no means to avoid overexposure in TAV mode after it exhausted this minimal ISO setting.

P.S.: I guess you mean +0.3 EV exposure compensation; +(0)3 EV would indeed be way too much for most scenes.


Last edited by Class A; 11-16-2014 at 07:37 PM.
11-16-2014, 07:58 PM   #9
Loyal Site Supporter
Mikesul's Avatar

Join Date: Sep 2009
Location: Phoenix, AZ
Posts: 2,655
Original Poster
QuoteOriginally posted by Class A Quote
As LensBeginner pointed out, the use of "ISO 100" could indeed be the clue to the source of your problem.

The K-3 cannot go below ISO 100, so has no means to avoid overexposure in TAV mode after it exhausted this minimal ISO setting.

P.S.: I guess you mean +0.3 EV exposure compensation; +(0)3 EV would indeed be way too much for most scenes.
Thanks guys but all of the responses miss the point that it was TAV with a high shutter speed and moderate aperture. It was not set at ISO 100 that is what the camera set. Furthermore when I changed to aperture priority with the same settings, same scene the picture was properly exposed. Anyway, it appears no one has seen the erratic behavior I described so thanks for your help. Yes the 03 was a typo for 0.3.
11-16-2014, 08:28 PM   #10
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 9,193
QuoteOriginally posted by Mikesul Quote
Thanks guys but all of the responses miss the point that it was TAV with a high shutter speed and moderate aperture.
We did not miss that point.

QuoteOriginally posted by Mikesul Quote
It was not set at ISO 100 that is what the camera set.
Exactly.

Do you see that the camera could not get any lower with the ISO?

When you get ISO 100 in TAV mode on a K-3, you either are lucky when the required ISO is ~100 for a good exposure, or it means you get an overexposed image.

I'm not saying that I know what happened and your comment regarding Av mode seems to suggest there is something else going on, but I hope you can see that LensBeginner offered a plausible explanation.

If you were really keen to investigate, you could use PhotoMe (or similar) to read out the metering information for the overexposed photos. If the metering segments show overexposure and the ISO is at 100 in TAV mode, it seems to be unambiguous that the camera just had no chance to avoid the overexposure.
11-16-2014, 08:58 PM   #11
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,684
I agree with Class A and LensBeginner. The camera couldn't close the aperture or increase shutter speed because you were controlling those. It did what it could by dropping ISO to the minimum. In other words, you forced the camera to overexpose by using aperture and shutter settings that were too bright for ISO 100.

If there's a chance you will be using base ISO in TAv mode, you need to monitor exposure. The settings will flash in the viewfinder to indicate overexposure at the selected settings.

Last edited by audiobomber; 11-17-2014 at 05:27 AM.
11-16-2014, 10:43 PM   #12
Pentaxian




Join Date: Jan 2011
Location: New York
Posts: 3,310
QuoteOriginally posted by Mikesul Quote
Thanks guys but all of the responses miss the point that it was TAV with a high shutter speed and moderate aperture. It was not set at ISO 100 that is what the camera set. Furthermore when I changed to aperture priority with the same settings, same scene the picture was properly exposed. Anyway, it appears no one has seen the erratic behavior I described so thanks for your help. Yes the 03 was a typo for 0.3.
QuoteOriginally posted by LensBeginner Quote
Maybe there was way too much light for auto ISO to cope? If you were fully open and with a low enough shutter speed the camera could have tried hard to keep the exposure under control by lowering the ISO, but couldn't go past 100...
LensBeginner didn't miss the point! @mikesul, you said you had TAv set to 1/500 second at f5.6. If it was a sunny day TAv might have bottomed out at ISO 100 and still overexposed. The exposure settings were probably blinking to warn you that TAv mode couldn't get an acceptable exposure. You might have needed to go with a faster shutter speed.
11-17-2014, 10:16 AM   #13
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,436
QuoteOriginally posted by Mikesul Quote
Not really, +03 has minimal effect.
On my K-3 and my K10D before it, +3 provides 3 stops of additional exposure. I noticed the additional comments and that you meant +1/3 stop which would be very little.


Steve

---------- Post added 11-17-14 at 09:20 AM ----------

QuoteOriginally posted by Mikesul Quote
It was not set at ISO 100 that is what the camera set.
Yes, that is how TAv works. You set aperture and shutter speed and the camera sets the ISO. There are limits at both the upper and lower end, however.

Was the display blinking (exposure out of range) by any chance?

I don't think there is enough information to determine what is happening here. Please attempt to reproduce and post the photo with all exif intact (use in-camera JPEG).


Steve

Last edited by stevebrot; 11-17-2014 at 10:22 AM.
11-17-2014, 11:16 AM   #14
Pentaxian
audiobomber's Avatar

Join Date: May 2008
Location: Sudbury, Ontario
Photos: Albums
Posts: 6,684
QuoteOriginally posted by stevebrot Quote
I don't think there is enough information to determine what is happening here. Please attempt to reproduce and post the photo with all exif intact (use in-camera JPEG).
I think what happened is perfectly clear. There have been several threads like this, where people don't realize that the camera will not override the aperture of shutter speed settings in TAv mode. If the settings require less than ISO 100, the camera will overexpose.

What is the purpose of specifying in-camera jpegs? The exposure will be the same, whether raw or jpeg.
11-17-2014, 11:34 AM   #15
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,436
QuoteOriginally posted by audiobomber Quote
What is the purpose of specifying in-camera jpegs? The exposure will be the same, whether raw or jpeg.
The purpose is that exif is often stripped on export after processing RAW. This happens all the time. I suggested a photo with exif because the problem description was vague.

I agree that it is extremely probable that the problem is simply overrunning the exposure capabilities of the camera. That is why I asked if the display was blinking. There are at least two or three problem threads a month where there is a complaint of over/underexposure and the blinking display had been ignored.

Translation: I think you, along with lensbeginner and Class A, are very probably correct, sorry you did not pick that up from my previous comment.


Steve
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
behavior, camera, exposure, iso, mode, pentax help, photography, photos, post, settings, steve, tav, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Forum contest and odd forum behavior tvdtvdtvd Site Suggestions and Help 3 11-03-2014 03:30 PM
crazy shutter behavior kona49 Troubleshooting and Beginner Help 7 05-11-2014 08:22 AM
Error Odd Quick-Reply Behavior Parallax Site Suggestions and Help 13 09-17-2011 03:41 PM
Odd Tamron Lens Behavior - Advice Please? krs Pentax SLR Lens Discussion 10 10-21-2009 11:05 AM
Odd behavior THAN THE SWORD Pentax DSLR Discussion 2 09-10-2009 05:36 AM



All times are GMT -7. The time now is 08:04 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top