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09-21-2010, 10:02 AM   #1
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K-x exposure question

Hello fellow pentaxians,
I got back from my amazing first trip with my K-x. In general I'm very happy with the results. I was a bit over-enthusiastic of my new camera and shot about 1400 pictures in two weeks...

I've got a question: almost all the time I was shooting on 'P' mode with center-weighted AF. Sometimes playing with the EV button.
When going over the photos in Aperture I found myself too often using the "shadows" slider to brighten closer darker areas. See these examples (before using the 'shadows' tool):
Picasa Web Albums - Yotam - Pyrenees 2010...
Picasa Web Albums - Yotam - Pyrenees 2010...

Another issue I had during the trip was that when shooting in the outdoors the K-x LCD screen looked too dark, caused me to think that my photos are underexposed (when looking after shooting, didn't use live view). I then started to shoot with +1EV almost all the time and only when I got some time to review my photos (after a day or two) I realized most of them are overexposed... Until the end of the trip it was sometimes hard to decide the correct exposure, so I found myself sometimes using the bracketing tool for these hard-to-decide scenes - so when I got home I chose the best exposure photo from each shot (HDRing them is not an option as I didn't use a tripod). Any tips on how to overcome this issue?

BTW. one day during the trip I saw another pentax owner and was really excited after meeting so many Canon/Nikon photographers...

Thanks,
Yotam

09-21-2010, 12:24 PM   #2
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You might want to review your first image with histogram displayed, and then you can adjust EC to get correct exposure for the next shots .
09-21-2010, 12:39 PM   #3
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Your second concern first. The LCD is a poor tool to use for image quality review. It's really only good (IMO) to make sure that what you wanted in the frame, is there.

As to your exposure problems. The 2 images you linked to, are not problems at all. That is, the camera did exactly what you told it to do. A scene like that you're going to have to choose at times between black detail-less shadows, or a blown out sky. I would suggest, even if just for a learning exercise, switching to Spot metering and studying a bit what the camera's meter readings really mean.

For scenes like the two you show, I would handle in one of 3 ways.

Meter the shadowed area and expose for that
Move closer and widen the lens up to get rid of the shadowed area all together or use a longer lens, for the same result on the shadowed areas.
Crop it out.

My Personal preference of the 3 would have been the first. If you were to meter the shadows, adjust your exposure down 1-2 stops from there, you would then be able to brighten the other areas and have some decent detail in the shadows remaining. Doing any of this however requires going full manual exposure (M) mode. Your first shot, the mountain shot, demonstrates nicely what I don't like about using CW metering. That is the same situation as if you were in an open air shelter on a bright day, taking photos of the people inside. You will end up with a bunch of shadows and a perfectly exposed outside (of the shelter). That's a lesson I learned in the film days when one couldn't just retake the shot.

That's my 4

09-21-2010, 01:53 PM   #4
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Using the histogram can be a good tool.
Also you may turn on high light and dark area detection in pre-view (I do not have an K-x, but all my Pentax DSLR's can do that), it will flash blue or yellow where the picture is under / over exposed.

Your problem is that many picture during mid day in bright sun light have a lot of dynamic range. Much more than a computer display can handle, so yo uwill see a lot of dark areas.
This effect is worsen if you have one of these modern monitors with a high dynamic contrast (the monitor will beef up the contrast), if you have that, turn dynamic contrast off and try to calibrate the monitor.
There are some free tools for that on the Internet.

Now you want to see more of the shadow parts, you can up that in (for instance) Lightroom rather easily.
You will however compress the actual dynamic range with that.
Another option is to use HDR.
Can a K-x do shadow compensation?

Besides overexposing / blowing out high lights, there is no other option.

- Bert

09-21-2010, 09:48 PM   #5
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The K-X has a very high dynamic range, but to make full use of it you should use RAW. You can use RAW + JPG mode to get both files on your card, but my usual workflow is to set the format to just DNG-raw.

when I'm back home I extract the jpegs from the RAWs with the supplied Pentax DCU program (look under tools).

The extracted JPEGs are compact low quality, but you'll not notice that unless your are zooming to 100% and even than you'll have to look hard. They are fine for display on your computer.

The next step is that I use DCU (or another program like LightRoom or Bibble) to only redevelop those DNG images with exposures I don't like. Lower/increase the exposure, adjust white balance, add shadow compensation. (Note that you could probably also use Picasa on your PC for all of the steps above. I've not tried it with the K-X, but in general I didn't really like the colours picasa produced from my K10 raw files).

I find that using the K-X in matrix mode often results in the correct exposure, sometimes even a bit over exposed. Because I like details in the clouds in the sky, I often use the DR mode of the K-X. In that mode you camera will use ISO 200 under the hood, but use ISO400 exposure times, so halving the exposure. This will give slightly more noise, but that's no problem with the K-X.

The images are still really clean.

Last edited by tomtor; 09-21-2010 at 11:26 PM. Reason: Added picasa
09-22-2010, 07:17 AM   #6
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thanks for the answers!
I will read about the metering issue and try to use spot metering instead of center-weighted. I don't really understand this topic yet...
I actually shot some of the pictures on the RAW+JPG mode (it takes so much memory so I did that only when I predicted a very nice result). Though, I haven't looked at them as for web publishing I was pretty satisfied from the JPGs.
BTW, is there a reason to prefer DNG over PEF besides Adobe compatibility? I shot on PEF as it was the default...

HDR/bracketing is not a real option for me as I don't travel with a tripod.

I just don't remember this happened so often when I used a P&S. Probably this is one of the things I have to learn now with a DSLR, or maybe it is just an issue of metering (in my P&S there was only spot metering AF and I used to point it to the shadowed areas when focusing to get them exposed correctly - maybe I misused the center-weighted).
It was also surprising that the simple "shadows" adjustment in Aperture improved the images so much without HDR - why wouldn't the camera itself do it...?

tomtor - what is DR mode?
09-22-2010, 08:21 AM   #7
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QuoteOriginally posted by yotam Quote
thanks for the answers!
I will read about the metering issue and try to use spot metering instead of center-weighted. I don't really understand this topic yet...
I actually shot some of the pictures on the RAW+JPG mode (it takes so much memory so I did that only when I predicted a very nice result). Though, I haven't looked at them as for web publishing I was pretty satisfied from the JPGs.
BTW, is there a reason to prefer DNG over PEF besides Adobe compatibility? I shot on PEF as it was the default...

HDR/bracketing is not a real option for me as I don't travel with a tripod.
First, Bracketing IS an option, even without a tripod. The processing software that you use to combine them (into an HDR type) will automatically align everything (or at least Photoshop does). The only thing about it is if there is a moving object in the frame. Note the blue Absopure truck in the middle of the frame.



This isn't what I would call an HDR photo but it was the result of 4 (I think) bracketed shots combined in Photoshops HDR Merge.

OR, one of the brackets may give you the shot you want. In camera HDR (K7, Kx) does need a tripod or something sturdy to set the camera on. (it would also be nice if they allowed 2 second timer and mirror lockup with that feature)

PEF vs DNG. I don't have a personal preference (meaning I wouldn't tell anyone to use one over the other) although I use PEF exclusively. With PEF you need software that can read it. With Photoshop programs for instance you need to have the ACR module (provided by Adobe) installed that will read the PEF from your camera. The rub in that is, they don't do backward compatability. That is, to read the K7 and Kx PEF files, you need photoshop CS4 because the only support it in ACR 5.0 and later. I would imagine, that they will only support the K5/Kr in ACR 6 or later which requires CS5. There are freebies out there that will read the Pentax PEF. This is true with All camera brands, not just Pentax. With a DNG, you only need to be able to read a DNG. The advantage of course is you can grab just about any DNG capable software, and use it without worry of upgrading.

09-22-2010, 09:27 PM   #8
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QuoteOriginally posted by tomtor Quote
Because I like details in the clouds in the sky, I often use the DR mode of the K-X. In that mode you camera will use ISO 200 under the hood, but use ISO400 exposure times, so halving the exposure. This will give slightly more noise, but that's no problem with the K-X.

The images are still really clean.
QuoteOriginally posted by yotam Quote
I just don't remember this happened so often when I used a P&S. Probably this is one of the things I have to learn now with a DSLR, or maybe it is just an issue of metering (in my P&S there was only spot metering AF and I used to point it to the shadowed areas when focusing to get them exposed correctly - maybe I misused the center-weighted).
It was also surprising that the simple "shadows" adjustment in Aperture improved the images so much without HDR - why wouldn't the camera itself do it...?

tomtor - what is DR mode?
In the config setup screen which you get when you press info twice, there is an option DR200. That's the DR mode I was discussing.

Many P&S expose brighter than DSLRs, but the problem is that you than loose detail in brightly lit areas. The clouds, white buildings, but worst often also the skin of peoples faces in the sun when there are dark areas in the same image. You cannot recover that in post processing, also because most P&S cannot produce raws which offer more post processing options. Note that when you use the default matrix metering mode of the k-x that this will normally result in brighter images than the weighted-average mode you used.

The advantage of brighter (P&S) images is indeed that you get more detail by default in the shadows.

The K-X could indeed raise the shadows more. In the same setup screen which contains the DR200 mode is a shadow compensation mode (I believe to the right of the DR200 mode) that exactly does that!

The disadvantage of always raising the shadows is that you will also loose the deep blacks and some room is taken from the midtones and highlights, so you will loose some detail there. In higher ISOs you'll also get more noise in the shadows. When you have the RAW you can always change your preferences later.

Note that I used RAW+JPEG in the past, but I stopped doing that because of the space it takes on the memory card. Without the jpeg, the raw file is not that much larger than the jpeg. EG the average jpeg is 6mb and the average raw is about 10mb. I find that an acceptable size increase, for the advantages it offers when you take that special image. Often the occasion is gone when you want to reshoot it and then you're glad you have the raw image to work on.


Last edited by tomtor; 09-22-2010 at 09:45 PM.
09-22-2010, 10:10 PM   #9
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I generally just set -1/3 EV + multi segment metering and it's usually fine.

However if I'm shooting from the shadowy place then sky spots (f.ex. in trees) are highly overexposed and somewhat damage the image around them. So in such cases it makes sense to use spot measuring and AE lock button - point to the brightest spot and push AE lock. But then it makes sense to use +1 EV or the majority of picture will be underexposed.

Of course there are lots of nuances for each kind of lightning, you need to learn to choose best technique for current conditions. Just shoot several pictures of each scene, while varying exposition and when developing, see what settings did you use for the best shot you got - experience will come.

As of the format - I just use RAW only setting since you don't really need JPG to preview images in the camera, and when I load them into the computer, I can work with RAW right away.

RAW is important since you can pull the shadows from within about 2-3 EV underexposed, with the cost of some noise. So you can expose for the sky and have both colored sky and useable rest of the image. Of course if you don't want ANY noise in the shadows, it makes sense to use HDR techniques like bracketing, but the resulting motion blur makes it impossible to use sometimes.

Last edited by olenl; 09-22-2010 at 10:19 PM.
09-22-2010, 10:29 PM   #10
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Is 1400 pictures in two weeks a lot? I've had mine for a little over a month and have taken almost 7000
09-23-2010, 01:59 AM   #11
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Thanks for all the answers! You guys are so helpful!

QuoteOriginally posted by SirJangly Quote
Is 1400 pictures in two weeks a lot? I've had mine for a little over a month and have taken almost 7000
My friends say it is a lot, I don't really care...
09-24-2010, 08:50 AM   #12
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Hi looking at your two samples I would say they were slightly underexposed. living and working around various parts of Europe the average day very rarely, even in early morning rarely produces that deep blue sky with all the polution in the air.
However as has been pointed out the LCD screen is best used as a composition checker and not for reasons of light on the screen ect a exposure guide. Learn to use and understand your histogram display it is your best friend that you have!!
Use as suggested the highlights and shaddows warning on your reviwes BUT, learn what th camera shows and what you see on the computer are not the same.
Also remember when the lcd shows a image it is in fact a jepg simulation not a raw. If you don't belive that then shoot some high dynamic shots in both. Remember what your display showed as far as blown highlights then look on your pc at both types with the hightlights warning on . The jepg will typically show blown highlights similar to your camera screen but the raw on the pc will not be as blown.
Always take bracketed shots normal and either over and under or both over sligtly or whatever. with my k10 it is always normal plus 2 shots under as I find to my taste it overexposes.
Always bear in mind that you can recover a lot more detail from shadows but rarely as much from highlights that are equally incorrectly exposed.

Use either jepg or raw but unless you are printing very large high definition prints jpeg from the camera you will find are more than satisfactory.

Re. your question of raw types, pef is pentax version, dng is the adobe one either will do, there have been huge heated debates over the years on which is best and over raw vs jepg and I don't want to start another one. Only you can decide what you want to use and which system you are happy with.
Adwb
09-25-2010, 06:30 AM   #13
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Thanks Adwb for the detailed answer!
09-25-2010, 07:37 AM   #14
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QuoteOriginally posted by yotam Quote
Thanks Adwb for the detailed answer!
your very welcome it's why we read the posts to learn and to help.
adwb
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