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06-01-2015, 01:16 AM - 1 Like   #1
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Random overexposure problem getting worse!

Hello

I tried searching the forum, and it appears this is a problem others have experienced too - but I failed to find any solutions or suggested actions. Maybe I need to send my K3 in for service, but I hate being without it!

Actually, this has happened with both my K5-II and my K3, which might point to the problem being me rather than the camera - but after yesterday I think I have enough data to rule that out.

I usually have my cameras on burst mode, since I shoot a lot of birds and wildlife where you need multiple shots to get the right angle/expression etc, and you can't instruct your models. For a while now on my K5II, I have had one out of a series become randomly overexposed to the point of completely blown highlights. I have ignored it: I bought it second hand, so there is no warranty anyway, and I just deleted the blown out ones and chose my keepers from the rest.

But now my K3 began doing it as well - and yesterday it went horribly wrong, destroying an ENTIRE beautiful series of a stoat hunting for mice while a wagtail followed it around making alarm calls. Since the problem began, I switched from spot metering to multi-segment metering (I thought a dark object with bright surroundings might be what caused it), but this did not help. Here are some samples of my stoat-series (no processing except jpg conversion and scaled to 1024 pix width). TAV-mode, center focus.

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06-01-2015, 01:35 AM   #2
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Why ISO 3200 - and 1/2000 sec?
06-01-2015, 01:40 AM   #3
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rawr - you should ask my camera. They are shot in TAV-mode, 1/2000 because I did moving subjects in bright sun. ISO 3200 is NOT my choice.
06-01-2015, 01:47 AM   #4
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QuoteOriginally posted by MetteHHH Quote
ISO 3200 is NOT my choice.
Yes it is. You manually set aperture and shutter speed, which is what TAv does, then you allowed the camera [drove the camera] to choose ISO 3200.

If you set a lower shutter speed (1/750 would have been plenty for that scene), ISO would have come down a lot. You are seeing here blown highlights in a very bright scene.

06-01-2015, 02:23 AM   #5
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You can also change the ISO range for ISO Auto and decrease the max value, then set shutter speed accordingly. Or perhaps use the M mode.
I had some issues with overexposing as well but found out that I had followed the recommended settings in the PF review which contained assigning exposure bracketing to button Raw Fx so from time to time I accidentally pressed Raw Fx without knowing it and got +0,3 EV resulting in overexposure.
06-01-2015, 03:12 AM   #6
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I have had the same problem with my K5-IIs. FWIW I was using a brand new Tamron 70-200 f2.8 lens when I first experienced it. The first photograph was dead on. Then it started overexposing. I am not sure of the cause, but it only happens in TAV. It ruined a series of shot of the Blue Angels. I have not seen it on my K3 yet. For me. the first shot is always okay. After that, exactly what you have. It is random and frustrating. For that reason, I have pretty much given up on TAV.
06-01-2015, 03:25 AM   #7
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QuoteOriginally posted by gaweidert Quote
TAV
TAv with a conservative auto-ISO ceiling, or a low manual ISO, would work fine.

In P mode for the scene above, (or one of the Green modes) with no human intervention the camera would probably have set IS0 to 200, shutter speed to 1/500-1/1000, aperture to f8 or f11.
06-01-2015, 07:23 AM   #8
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Make sure your aperture blades are snappy. If they aren't, your aperture is likely not closing fast enough during exposure.

---------- Post added 06-01-15 at 09:25 AM ----------

Also, make sure you don't have the EV compensation inadvertently cranked up.

06-01-2015, 07:26 AM   #9
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Both cameras? Same lens, by any chance? Is it possible that your lens is not stopping down for the exposure?


Steve
06-01-2015, 07:29 AM   #10
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QuoteOriginally posted by MetteHHH Quote
Hello

I tried searching the forum, and it appears this is a problem others have experienced too - but I failed to find any solutions or suggested actions. Maybe I need to send my K3 in for service, but I hate being without it!

Actually, this has happened with both my K5-II and my K3, which might point to the problem being me rather than the camera - but after yesterday I think I have enough data to rule that out.

I usually have my cameras on burst mode, since I shoot a lot of birds and wildlife where you need multiple shots to get the right angle/expression etc, and you can't instruct your models. For a while now on my K5II, I have had one out of a series become randomly overexposed to the point of completely blown highlights. I have ignored it: I bought it second hand, so there is no warranty anyway, and I just deleted the blown out ones and chose my keepers from the rest.

But now my K3 began doing it as well - and yesterday it went horribly wrong, destroying an ENTIRE beautiful series of a stoat hunting for mice while a wagtail followed it around making alarm calls. Since the problem began, I switched from spot metering to multi-segment metering (I thought a dark object with bright surroundings might be what caused it), but this did not help. Here are some samples of my stoat-series (no processing except jpg conversion and scaled to 1024 pix width). TAV-mode, center focus.
What happens when you set the mode to P? Same result?
06-01-2015, 08:32 AM   #11
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rawr, come on, saying that my settings forced ISO3200 is just silly. This has been my favoured mode since I got my K-10d.

I use TAV all the time to allow me to pick a depth of field I can live with, a shutter speed that keeps fast moving subject blur-less and then let the camera pick the ISO for the circumstances. THAT is what TAV does. It is the program of choice for wild life for the same reason.

Suggesting 1/750s just tells me you don't shoot a lot of birds.

Yes, I could restrict the ISO - but then when I suddenly spot a fox under some trees, or a nightingale in the shade, I am not prepared. The whole beauty of TAV is that it lets the camera compensate the exposure by varying the ISO.

Why on earth would f5.6 and 1/2000 force ISO 3200? Here is another couple of shots from yesterday where the camera did not act up. This is what SHOULD happen (shots at the end of the message):

---------- Post added 06-01-15 at 08:43 AM ----------

QuoteOriginally posted by Samoht Quote
You can also change the ISO range for ISO Auto and decrease the max value, then set shutter speed accordingly. Or perhaps use the M mode.
I had some issues with overexposing as well but found out that I had followed the recommended settings in the PF review which contained assigning exposure bracketing to button Raw Fx so from time to time I accidentally pressed Raw Fx without knowing it and got +0,3 EV resulting in overexposure.
Thanks, Samoht, I might resort to restricting the ISO - it just seems silly to have to. Using M mode won't give me the versatility I am looking for - I really like to be able to focus on the action when I am birding, rather than constantly checking camera settings.

QuoteOriginally posted by gaweidert Quote
I have had the same problem with my K5-IIs. FWIW I was using a brand new Tamron 70-200 f2.8 lens when I first experienced it. The first photograph was dead on. Then it started overexposing. I am not sure of the cause, but it only happens in TAV. It ruined a series of shot of the Blue Angels. I have not seen it on my K3 yet. For me. the first shot is always okay. After that, exactly what you have. It is random and frustrating. For that reason, I have pretty much given up on TAV.
Oh - that IS discouraging. TAV is my favourite Pentax feature - I really don't want to give up on it.

QuoteOriginally posted by darylk Quote
Make sure your aperture blades are snappy. If they aren't, your aperture is likely not closing fast enough during exposure.

---------- Post added 06-01-15 at 09:25 AM ----------

Also, make sure you don't have the EV compensation inadvertently cranked up.
Actually, since this began with my K5-II I have kept it pretty much constant on -1EV. It only happens on single shots in a multi-exposure series usually, the stoat was the first all-blown-out-series I have had.

QuoteOriginally posted by stevebrot Quote
Both cameras? Same lens, by any chance? Is it possible that your lens is not stopping down for the exposure?

No, when I go birding I keep my K3 with the DA*300mm and my K5-II with a 100mm macro for bugs and bees - with the K5-II it has happened with my Tamron 28-75mm as well, and my Sigma 28mm. This was the first time my K3 let me down this way...

Steve
QuoteOriginally posted by IchabodCrane Quote
What happens when you set the mode to P? Same result?
I haven't had the problem in P mode - but I have to say I rarely use it. For family setting etc. I usually use Av, and it HAS happened in that setting. Usually I delete the blown out ones, so I did not hang on to a lot of documentation...

THanks a LOT for all your helpful comments. I suppose I will see how the situation develops: I still have a year and a half warranty on my K3.
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Last edited by MetteHHH; 06-01-2015 at 08:43 AM.
06-01-2015, 08:47 AM   #12
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QuoteOriginally posted by MetteHHH Quote
it lets the camera compensate the exposure by varying the ISO.
Exactly right. But you set it up so that the camera had no other option but to ride high up into ISO 3200, where blown highlights are a great risk. Exposure triangle, histogram etc.

QuoteOriginally posted by MetteHHH Quote
This is what SHOULD happen:
As far as I can see, the camera is simply basing it's response in a way that is appropriate for the light and colour of the scene - in all of the images above.
06-01-2015, 08:57 AM   #13
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QuoteOriginally posted by rawr Quote
Exactly right. But you set it up so that the camera had no other option but to ride high up into ISO 3200, where blown highlights are a great risk. Exposure triangle, histogram etc.



As far as I can see, the camera is simply basing it's response in a way that is appropriate for the light and colour of the scene - in all of the images above.
rawr, sorry for being slow, but I don't get this at all: WHY would the camera conceive ISO 320 as "appropriate for the light and colour of the scene" for the marsh harrier and ISO 1600 as "appropriate for the light and colour of the scene" of the shoveler, resulting in well-exposed images, but ISO 3200 as "appropriate for the light and colour of the scene" for the stoat - blowing it out completely?

Remember I used multi-segment metering. ISO 3200 is very much INAPPROPRIATE for the light and colour of the scene, as the result demonstrates.

I did nothing different for the harrier or the shoveller.
06-01-2015, 09:20 AM   #14
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I see this when the automatic aperture is not closing quickly enough. I have several Adaptall-2 PK/A adapters. Some of the give me erratic exposures and some work well.

I routinely test for the bad adapters by shooting a quick sequence of several images with a fast shutter speed and higher f-stop (say f/11, f/16). When I review the sequence on the LCD screen, it is obvious if the adapter/aperture is functioning properly or if the exposures are erratic.

I test for sticky apertures in other lenses the same way.

A second thought. Is the overexposure as bad on RAW images? When I shoot RAW+, my JPGs often show blown highlights when the RAW does not.

Hope this helps.

Cheers,
Lou
06-01-2015, 10:38 AM   #15
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Thanks Lou

I would hate if there was anything wrong with my DA*300 - that would be worse than a K3 malfunction! But - I am thinking - if the problem had been slow aperture blades, wouldn't my exif still look like for instance 1/2000s, f 5.6, ISO 640, but the actual exposure being longer due to the slow blades?

My raw images DO look overexposed when I load them into lightroom but, WOW, shooting in raw definitely saved me this time! Here is a shot post processed with -2,4 EV and a bit of Topaz clarity - this is quite keepable, actually! I never thought the highlights could be restored this well!
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