K30 - Some shots seemed underexposed

Hi all

After reviewing the many photos from our holidays, I have found that some of the shots seem underexposed. It seems to be mainly the shots in the swimming pool.

After some reading, I understand that poorly lit swimming pools are a difficult environment for taking photos, but this one is under a large glass dome, and very well lit.

I'm wondering however, if the problem is that there was so much light reflecting off the water, and the various white surfaces, that the camera was just trying to compensate, as the photos with less water, and more background, seemed to come out a lot better.

Here is an example image.

Seems underexposed

And one taken immediately after, which seemed to come out just fine.

Looks a lot better to me

I'm trying to understand the histograms. Neither one has any clipping at the left, but the first one doesn't really show anything to the right of the centre line. Does that mean it's definitely underexposed?

Any and all input is much appreciated.
Neil

The first is under exposed as you've pointed the camera at a universally bright area. Therefore the camera thinks it's too bright and reduces exposure.

The second has a large dark area that helps compensate, so the average of all the tones works out about right.

Use exposure compensation as needed to correct for uniform areas such as image one.

Use the Pentax software to adjust the exposure - a simple task and then re-save the image.

Thanks John. I had a feeling it was user error, but just wanted to be sure

I thought at first, it was just that I'd set the shutter speed too high (using tv mode), but everything else was on auto, and the camera was still picking a relatively low ISO (200), so then I figured it must be something else.

I shall have a play with exposure compensation and see what results I get in various situations.

Thanks Gamka, I'll definitely do that in iPhoto, or Aperture if I decide to buy it

I just wanted to be sure it was something I'd done wrong, and not a problem with the hardware

It is more a case of selecting te metering mode or point. Quite often when I have issue with varying light across the subject I set the camera to Bracketing mode with a suitable +/- 0.3 or 0.5 set of 3 or 5 exposures and can then select the best.

Or take a shot, then check the histogram in display mode, and take another shot with the required exposure compensation.

Thanks guys.

@Gamka
I had a quick play with bracketing whilst I was away, but I'll definitely give it a try when taking photos of universally light or dark areas.

@darkskies
I've only just found the histogram feature, but I think I'll be using it a lot in the future

Just tried a few shot of my car with bracketing set to +/-0.7. It's a dull day here, and the shots with +0.7 seem to be the most accurate.

Is this normal for a dull day, or is it likely reflections from the car causing the underexposure this time?

Is there any chance at all that the camera isn't metering correctly?

Looking through all the photos I've taken with the camera, and checking the histogram, I'm noticing that a lot of them, even the ones that look properly exposed (to my eye), have nothing showing in the right-most quarter of the histogram. The data at the far left isn't clipped, but all the information seems to be restricted to the first 3 quarters.

I read that if the right of the histogram was flat, even thought the left wasn't clipped, then that also meant the image was underexposed. Is this true?

It depends on the image, a histogram only shows you how many pixels there are at each brightness level. Now if this is an image of a very dark subject, the histogram should be all over to the left.

To learn how to use the camera meter, I wouldn't suggest starting with spot metering. Try centre weighted first. Take shots of various subjects, bright and dark ones, and use exposure compensation to take images at -1EV and +1 EV. Check the results carefully against the image and the histogram to see the effect. The try at half or third of a stop increments to fine tune how you like your images.

There are lots of good books on exposure and no doubt lots of simple web resources too. All worth a look.

Thanks again John, I'll take your advice, and hit google for some info on exposure

Having a read around, it seems that pentax dslr's are well known for under exposing in certain situations. It's not something I came across when looking for reviews, but with the right terms, Google pointed me to a few threads about it.

I guess the bottom line is, the camera won't get it right all the time, and some post processing may be necessary from time to time. I knew I wasn't buying a point and shoot, and it's already giving me better photos than we would have ever gotten from my old compact, so I definitely think it'll be worth the time and effort

With digital imagery one wants to be careful not to 'blow' the highlights as no post processing can recover them. Pentax seem to err on the side of caution by programming their computers... oops cameras... to under expose a bit and thus avoid blowing the highlights but then, as a result, leaving their images needing a tweak in post processing. It is something that is seen as a positive feature by some and a flaw by others. With my Canon compact I permanently have it set on -2/3EV.

The histogram is heaven sent. It allows you to accurately assess blown highlights and compensate appropriately. Obviously, when editing the image the desired effect takes precedence, but when taking the image it is a hugely beneficial tool.

K.

Thanks for the insight womble

I'm going to spend the next few weeks playing with settings and examining histograms to see what works best for various situations.

I'm also going to pick up either aperture or lightroom, so I can fix the photos I don't get right

I do have one last question, out of curiosity. I've been flicking back through my photos, this time taking notice of all the different values. I noticed that a few of the photos I took at 1/500 shutter (set using tv mode) had an ISO of 800, and aperture set to f/8 (almost every other shot was f/5.6 at the same focal length). I'm just wondering, does it seem odd that the camera would choose to change the aperture rather than decrease the ISO?

Thanks again to you all!

I often shoot in places where the ambient light is extremely bright - and it can with most cameras cause underexposure.

I will normally set my camera to bracket at 0 +0.3 +0.7 or 0 +0.5 +1.0 and occasionally a five shot bracket from -0.3 to +1.0 or -0.5 to +1.5

I should then get a near ideal exposure which can be tweaked a little and slightly different view with wildlife - the camera noise sometimes makes them perk up and look towards me.

Most of my memory cards are 4GB which allows for about 60 sets of bracketed images which is reasonable for most situations. So, unless you only have 1 or 2 GB SD/SDHC cards, don't worry about running out too quickly.

Also, shooting in PEF allows a lot of flexibility in processing later on ... but having the right exposure can save time.

If the ISO is set to a specific setting, rather than Auto, it will not be automatically changed by the camera. You can engage auto ISO or, for more control, in TaV mode you can change the aperture and/or the shutter speed yourself, and the ISO will be adjusted to suit.