Underexposure Issue k10d

[chrswggl]

I'm sure this is a user error but I can't figure out where I messed up. I set up the camera in the back of a church to take pictures of a ceremony I would be participating in. I asked someone else to take pictures with it by simply pressing the shutter, no other adjustments were needed.

After the ceremony I went up to look at the pictures and every single one was underexposed by at least a stop and a half. I had put the camera in sv mode and set the ISO to 500. To obtain an optimal exposure, the camera would have needed to shoot at around 1/40 of a second. Instead, it was taking pictures at 1/80-1/160 of a second.

I can't for the life of me figure out why. The camera was in auto focus points and segmented metering. What's interesting to me is that although the focal length and lighting never really changed, the aperture varied from 4.5-5.6 from picture to picture. What's going on here?
--
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Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

 

[John Bean (UK)]

Not enough information to be helpful except:

After the ceremony I went up to look at the pictures and every
single one was underexposed by at least a stop and a half. I had
put the camera in sv mode and set the ISO to 500. To obtain an
optimal exposure, the camera would have needed to shoot at around
1/40 of a second. Instead, it was taking pictures at 1/80-1/160 of
a second.

If you knew the exposure in advance then why not set it on the camera? That way there would be nothing to go wrong.

What's "sv" mode BTW?

--
John Bean [GMT - is there any other?]

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[bobmax]

I've been shooting only in Av and P modes and without flash find my exposures "dead on" for my taste unless I mis-meter the scene w/something unusually "bright" when in matrix mode.

With flash, (my AF360) I have to compensate to +.7 to get exposures "I like", but at taht exposure compensation it is very very reliable (even in bounce). Only flash challenge I have is the AF360 does not "bounce far enough" due to lack of power. Will be getting a AF540 shortly.

Bob
--
BobNIK

 

[blende8]

1. What lens?

2. What was your setting for Program line? The default is "normal", but there is also "highspeed", MTF etc.

 

[chrswggl]

Sv mode is sensitivity priority. I set the sensitivity and the camera sets shutter speed and aperture. I didn't want to set the parameters in stone because I thought the camera would be able to make an educated decision. Somehow I was wrong...
--
http://picasaweb.google.com/chrswggl

Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

 

[chrswggl]

1. What lens?

It was the 50-200 f 4-5.6

2. What was your setting for Program line? The default is "normal",
but there is also "highspeed", MTF etc.

It's on normal
--
http://picasaweb.google.com/chrswggl

Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

 

[John Bean (UK)]

Sv mode is sensitivity priority. I set the sensitivity and the
camera sets shutter speed and aperture. I didn't want to set the
parameters in stone because I thought the camera would be able to
make an educated decision. Somehow I was wrong...

Ah, got you. A bit like "P" mode in that it sets both shutter and aperture.

Maybe you can post a sample to give a clue about what fooled it.

--
John Bean [GMT - is there any other?]

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[TMalford]

I think John is right. In conditions like this a nice approach is to shoot in metered manual, and take a few test shots in advance. Since the lighting conditions won't likely change, this is probably your best bet.

Regarding the underexposue issue, can't help you there.

T
GMT minus 8



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[chrswggl]

Ok i've posted some examples at the link in my signature.
--
http://picasaweb.google.com/chrswggl

Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

 

[John Bean (UK)]

Wow, underexposed for sure. There's no EXIF visible, can you tell me the shutter speed/aperture/ISO of each picture?

I don't know how Sv mode works, does it have limits on the settings it can use? Looks to me like not enough light for a slow lens at ISO500 without the shutter speed being really slow.

--
John Bean [GMT - is there any other?]

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[chrswggl]

I have added the exif in web albums.
--
http://picasaweb.google.com/chrswggl

Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

 

[John Bean (UK)]

Ok, I'm stumped. The first two are a full EV less exposure than the second two - which are about a stop underexposed anyway. I don't think it's very likely the camera just did that... why should it?

Are you sure there was no accidental button-pushing? What does the EXIF say for exposure compensation? Is it set to 0.0 on all four images?

If it's not finger trouble then there's a fault. Should be easy to reproduce under more controlled conditions if that's the case.

--
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[lol101]

Did you use the lens @ or near the long end?

With or without flash?

The only thing I can think of is a tele shot with flash from too far for the flash to reach...

 

[chrswggl]

Well what's interesting is that the first few pictures are closer to the correct exposure. There was one 1/60 s picture. But as time went on the camera underexposed more and more till it hit f 5.6 and 1/160 s, which is where it stayed for the remainder of the ceremony. It's like it was edging more and more towards a faster shutter speed.
--
http://picasaweb.google.com/chrswggl

Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

 

[chrswggl]

Nope the flash wasn't used and the focal length was about 100 mm.
--
http://picasaweb.google.com/chrswggl

Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

 

[lol101]

If the batteries were full charge and no exposure correction was done then... I'm lost!

 

[steephill]

the majority of the shot consists of white surfaces which has fooled the camera metering. This is a classic metering problem, like snow scenes or bright beach sand. The camera will assume that the average for the scene should be an average grey ( 18% grey) and underexposes turning whites grey. For these subjects you need to use exposure compensation to make whites white and an extra 1 to 2 stops is normally required. One solution would be to spot meter an average subject, like a human face, and use these readings on manual exposure mode.

So overall I would guess that your camera is working properly, it just needs more user input. I know that matrix metering is meant to be able to cope with a wide variety of scenes but the simple truth for Pentax at least is it doesn't. Auto exposure modes cannot guarantee a perfect exposure.

--
Steve

http://www.pbase.com/steephill

 

[*isteve]

Cant explain, but I suggest you test it our yourself and confirm theres a problem. On the face of it it looks way off. if it behaves the same indoors with you in control I'd take it back to the shop.

Sorry - these types of fault are infuriating I know, but then again when you habe the camera to someone else you never know.

Is it at all possible that they pressed the button half way then moved the camera?

Nope the flash wasn't used and the focal length was about 100 mm.
--
http://picasaweb.google.com/chrswggl

Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

--
Steve
Measurebating makes you short sighted.
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[chrswggl]

I had a suspicion it had something to do with no real 18% grey...

I don't really think it'll be a problem in other situations, but this certainly is a learning experience!

--
http://picasaweb.google.com/chrswggl

Pentax k10d, Pentax 50-200, Sigma 18-50 Macro soon...

 

[TMalford]

I'm wondering if, in sv mode, there are exposure parameters that were bumped up against. If the camera is reading focal length, it might, for example, be reluctant to expose slower than 1/160th at 100mm. Just a guess....

I think the lesson to be learned here though is, do some test shots in advance and/or when in doubt set the exposure manually.

I'd be interested in how the camera may have performed at say 800 or 1600 iso.

T
GMT minus 8



Without gravity, what would we do with water?
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