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02-06-2010, 12:03 AM   #1
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Pentax K-x Exposure Help

I have recently upgraded from the Pentax K100D to the K-x and am having trouble with images being over exposed. I think the K100D is a more entry level and forgiving camera and always took great shots, I think the the K-x is going require more skill to get things right.

An example below. I took these pictures on Table Mountain in the middle of the day. One is on auto setting and the path looks very white - f11 @ 1/100 sec. The second photo taken afterwards was on Aperture Priority with an F-stop of f9 but the shutter speed was also at 1/100 sec too and the picture is clearly over exposed.

Any ideas why there would be such a difference in the two images? Also any tips on the k-x and shooting in the middle of the day would be much appreciated.

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02-06-2010, 12:40 AM   #2
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QuoteOriginally posted by jeffski Quote
I have recently upgraded from the Pentax K100D to the K-x and am having trouble with images being over exposed. I think the K100D is a more entry level and forgiving camera and always took great shots, I think the the K-x is going require more skill to get things right.

An example below. I took these pictures on Table Mountain in the middle of the day. One is on auto setting and the path looks very white - f11 @ 1/100 sec. The second photo taken afterwards was on Aperture Priority with an F-stop of f9 but the shutter speed was also at 1/100 sec too and the picture is clearly over exposed.

Any ideas why there would be such a difference in the two images? Also any tips on the k-x and shooting in the middle of the day would be much appreciated.
I think you've partially answered your own question. At f9 you are letting in nearly twice as much light (at the same shutter speed) as you are at f11. Actually, f8 is twice the light. With a scene such as this, Something is going to be overexposed regardless of what you do (in most cases). What I would do with it is set to manual, meter for the brighter spots, and then use selective post processing to bring out the details in the shadows (rock formation). That should get you a properly exposed sky, your path won't be washed out beyond repair, and the end result will have an overall good balance to it. Keep in mind that there is a lot of room to bring out details in shadowy areas but once details are blown out (such as in your path), they are gone. This would apply regardless of the camera.

02-06-2010, 12:58 AM   #3
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Thanks for the reply. I will try to think about what to meter against a bit more - can you give me any tips on how to do this - would I point the camera towards the path, manually set the exposure against that and then point it back to take the shot.

With regards to my second photo - it was set to Aperture Priority so I would have thought the shutter speed would automatically adjust so that it was faster and the exposure would be similar to the first photo??
02-06-2010, 01:41 AM   #4
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Lots of good advice from Jeffjs. I only shoot in manual mode (99%) and highly recommend it. It allows you to have full control--the only way to fly. Always expose as far to the right as possible, without blowing highlights.

So, take a shot, then check your histogram right away for any clipping. Of course there are situations when blown highlights may be acceptable to you, especially when they do not figure into the overall makeup of the shot, or have no negative effect on the subject.

Once you get the original shot as best to the right as you can, then take that Raw file to PPing and make any adjustments you feel are needed.

Also, if you have a clear image of your subject in the shot say, in this example the trail, then you want to meter the scene such that the trail is metered properly, without much concern for the other areas of the scene. In fact, as I see this scene, having dark cliffs behind the trail may help to complement your subject even more, by defining it. But, this is only the case if the trail is your subject, it would change entirely if those cliffs were your subject. It is all up to you, you are the photographer, you have to make these choices, then make them work.

Remember too, at least on my K20d, there are 3 choices for metering--I imagine the Kx has at least 3 too. Which metering mode were you in?


Last edited by Jewelltrail; 02-06-2010 at 01:47 AM.
02-06-2010, 02:16 AM   #5
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QuoteOriginally posted by jeffski Quote
Thanks for the reply. I will try to think about what to meter against a bit more - can you give me any tips on how to do this - would I point the camera towards the path, manually set the exposure against that and then point it back to take the shot.

With regards to my second photo - it was set to Aperture Priority so I would have thought the shutter speed would automatically adjust so that it was faster and the exposure would be similar to the first photo??
Here is my basic workflow for something like this.

I set the camera to Manual exposure, Spot meter. The key is the spot metering and I find total control over the exposure better to handle. Note that spot metering is only possible in the center of the frame.

If there is textured white or near white or very bright in the scene, That is what I meter. Now Here is the trick and why I use Manual exposure. Adjust your exposure so the meter reads about 2 stops to the right. Remember, the meter is looking at a scene as shades of grey and the center (metered) area is Middle Gray, 18% (some say 12% but it really doesn't matter for this discussion). It doesn't see colors, textures, or anything else like that. The white in the scene could also be clouds in the sky.

Adjust shutter speed if you want to stop motion, adjust aperture if you want to change DOF, just remember to adjust the other accordingly (If it exists on the Kx, Program shift will do some of this for you).

This shot is metered on the clouds (for me they could get rid of matrix and center weighted metering and just leave spot, I use it exclusively).



It may help to carry a white card or a gray card with you and meter off of that (white, adjust your exposure, gray, will give you proper without adjustment in most cases).

Something is likely to look Underexposed but there will be plenty of detail left to work with. That's where the post processing comes in(see below). You could Also go the other way. If the detail in the rock formation is more important to you, meter that and drop the exposure 1 or 2 stops. It will likely leave you enough highlight detail to pull back and recover some.

Our digital cameras are great but the dynamic range (amount of usable detail from pure black to pure white) leaves something to be desired on one end or the other.

Post processing.. I suggest you seek out some tutorials on using layer masks. Most software will handle them and once you get the hang of it, it's fast and simple. What it will allow you to do is selectively adjust the Curves and apply it to different parts of the photo while leaving the rest alone. The more powerful software packages will give you greater control here. I'm currently using CS4 but most versions of photoshop will handle this (I've been doing this since version 5). If I may....



This is your Auto.jpg to which I've applied two simple layer masks and adjusted the curves on each. One to bring out the rock detail and the other to recover some of the path detail. Pretty slick tool IMO. There'll be a lot of situations where no amount of fiddling with the exposure will be perfect. It becomes a case of deciding what is important to you if you don't want to mess with the post processing.

If I've completely confused you on the exposure discussion, seek out some discussions on the Zone System. It if nothing else will show you how to read exactly what your meter is telling you and how to bring things around to your way of thinking.


Last edited by JeffJS; 02-06-2010 at 02:22 AM. Reason: Make corrections
02-06-2010, 02:38 AM   #6
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Thanks guys. I have had the camera set to multi-segment metering but will have a go with spot and metering to the right.
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