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03-28-2011, 01:14 PM   #1
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Questions re: WB and exposure

Got my first dslr (K-x) a couple months back and still at the learning stage re: digital slr photography. Although I've got most of the basics covered, I am still at times confused about some aspects re: the subjects of white balance and exposure. Further enlightenment is much appreciated.

All of the below assumes shooting in JPEG, not RAW.

WHITE BALANCE:
I fully understand the concept of white balance, color temperatures, and the importance of getting the white balance correct so all other colors will render as true as possible. I normally use AWB, but have also experimented with most of the other individual WB settings (daylight, shade, cloudy, etc.) depending on the setting I'm shooting.

My question is this. All things being equal, if I consistently use an 18% gray card to establish WB for each photo I take, does that mean there is no need to worry about AWB or any of the individual WB settings on the camera? In my simplistic way of looking at this, why go thru all the time and effort trying to set the proper WB if I can just take the lazy approach and use a gray card instead, and get it over with quickly and easily? Or am I overlooking other important considerations here?

EXPOSURE:
1. How is exposure adjusted if I am shooting in Manual mode, since the EV bar is not operational in Manual mode? Does this mean I would have to make exposure adjustments by changing aperture settings?

2. Is Scene mode really advantageous when faced with those specific conditions, or is it considered just a "quick and easy" way to get a "reasonably" good shot under adverse conditions? If one had time to setup the shot, then I would think manually setting other options (i.e. aperture, EV, etc.) would result in better photos. I have never shot in Scene mode and was just wondering if it is the lazy way to shoot (and I don't mean that to sound negative). Just curious what others think of the pluses/minuses of using Scene mode settings.

Thanks for anyone's thoughts on the above.

Stardog
Always learning...

03-28-2011, 03:02 PM   #2
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You can use the gray card to adjust WB later or use it to set a Custom WB that can be stored in your camera. With the K7 and K5, you can actually store 3 different custom white balances. I don't know about the K-x. Using a gray card for Exposure, you are matching the cameras meter to what it actually sees. That is, the meter assumes 18% gray (theoretically) regardless of what you are pointing it at. So if you are pointing it at a gray card, your exposure should be correct.

In M mode, with an A type lens, the EV bar (camera meter) should activate at half press of the shutter button. in M mode with an M type lens, (on the K20/7/5 anyway) you can activate it with the Optical Preview. I Live in manual mode and use this method all the time.

03-28-2011, 06:20 PM   #3
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Hi Stardog,

Changing AWB globally will have the same effect on color in any lighting, but since it meters and tries to correct each individual shot, there will be some variation from shot to shot as the content of the scene changes. The only way to get truly consistent color control (which may be considerably more picky than most individuals might need), you probably need to set a manual WB for each shot or set.

For Pentax, at least, Manual Exposure means just that. You take an exposure reading, and adjust the exposure accordingly. If there are some hotspots, and you need to correct for that, then the meter will show underexposure. In my mind Ev compensation or Auto ISO in Manual Exp mode doesn't make much sense.

The Scene modes give you different combinations of priorities in setting to get a predetermined "look" to the shot. At least in previous models with Scene modes, Auto Pict mode had the camera try to guess the mode from the scene content, and choose the most appropriate mode from the preset choices. They are all a convenience, but even advanced shooters might find that the presets might work well for different situations, and the ability to set a number of different parameters with one click of the dial may offer a definite speed advantage. There are times when someone might want to quickly change from an MTF (max resolution aperture setting for the lens) to a higher shutter speed priority program line.

I've seen some very good photographers suggest sometimes inappropriate seeming scene modes for certain kinds of shots. Sometimes creativity is expressed in not only what scene you capture, but how you use the features of the camera to capture a scene.

Scott
03-28-2011, 06:29 PM   #4
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QuoteOriginally posted by Stardog Quote
Got my first dslr (K-x) a couple months back and still at the learning stage re: digital slr photography. Although I've got most of the basics covered, I am still at times confused about some aspects re: the subjects of white balance and exposure. Further enlightenment is much appreciated.

All of the below assumes shooting in JPEG, not RAW.

WHITE BALANCE:
I fully understand the concept of white balance, color temperatures, and the importance of getting the white balance correct so all other colors will render as true as possible. I normally use AWB, but have also experimented with most of the other individual WB settings (daylight, shade, cloudy, etc.) depending on the setting I'm shooting.

My question is this. All things being equal, if I consistently use an 18% gray card to establish WB for each photo I take, does that mean there is no need to worry about AWB or any of the individual WB settings on the camera? In my simplistic way of looking at this, why go thru all the time and effort trying to set the proper WB if I can just take the lazy approach and use a gray card instead, and get it over with quickly and easily? Or am I overlooking other important considerations here?
First, IMHO, the 18% grey card would be better used to establish Exposure v. White Balance. As far as WB, if you're shooting strictly jpeg, I probably would use AWB for most outdoor shots. Indoor lighting is more tricky and AWB does not usually work as well as expected in these situations. I would simply take a quick photo indoors and then adjust the WB, after that you should be good to go until the light source changes.

QuoteQuote:
EXPOSURE:
1. How is exposure adjusted if I am shooting in Manual mode, since the EV bar is not operational in Manual mode? Does this mean I would have to make exposure adjustments by changing aperture settings?
Yes AND you can also change the suggested shutter speed as well. I would also try using the different metering options to fine tune things...

I am assuming you know how to use the manual setting on your Kx... I use a Km and K10, both have the "green" button to establish the correct shutter speed with the aperture you have selected. I am pretty sure your camera operated the same way. In fully manual, setting the aperture manually, and then using the "green" button, the camera sets the correct shutter speed, you can only alter the exposure by changing the shutter speed or aperture setting. In full manual mode you do not have the "Exposure Compensation" option available. (This example is if you're using any lens without an "A" setting or not using the "A" setting if available.)

However, if you are using manual mode AND your lens has an "A" setting on the aperture, then you should be able to see some kind of exposure meter going on your camera screen, either a bar or +/- exposure value. I am almost sure your Kx works like my Km, you can adjust both the shutter speed or aperture via the wheel...

EDIT: If your lens does have an "A" setting, I would encourage you to use the Av/Tv setting on your camera, this will allow you to use the "Exposure Compensation" option...

It's all a learning process and knowing your camera's optimum settings.
QuoteQuote:
2. Is Scene mode really advantageous when faced with those specific conditions, or is it considered just a "quick and easy" way to get a "reasonably" good shot under adverse conditions? If one had time to setup the shot, then I would think manually setting other options (i.e. aperture, EV, etc.) would result in better photos. I have never shot in Scene mode and was just wondering if it is the lazy way to shoot (and I don't mean that to sound negative). Just curious what others think of the pluses/minuses of using Scene mode settings.

Thanks for anyone's thoughts on the above.

Stardog
Always learning...
Shh, don't tell anybody, but I do use the "Scene" settings when taking quick shots of holiday lights or fireworks etc... but that's about the extent of it...

Good luck have fun - Rick

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