[Gooneybird]

Thoughts on achieving proper "exposure" on my Pentax K10D DSLR:
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Over the past nearly 18 months of using and enjoying this new DSLR camera, I've been
constantly evolving new tricks and techniques to use with it. Some of these tricks are
specifically suited to certain subjects, like taking telephoto shots of birds and other
wildlife. That application is what this writeup is largely about (even though I also use
the camera for many other subjects and themes.) Further, this writeup is largely
specific to the use of this camera with a newly acquired 180mm prime telephoto Macro
lens made by Sigma (but I am in the process of expanding the technique to my other
lenses as well.)

Prior to obtaining this new 180mm lens, the procedure that I had evolved with 3 other
lenses was to shoot mostly in AV mode, and set the lens aperture to something that seemed
reasonable for the particular shot (DOF), a moderate ISO to get a shutter speed to match
the subject. For example - I might choose f 4.5, ISO 400, and the camera might then select
a shutter speed of 1/60s. I would vary this, as needed, depending on the results as viewed
on the LCD. Due to the LCD's small size, judging the real quality was often nearly
impossible until seeing the images on the computer. My success in obtaining proper
exposure this way was often only about 60%, sometimes more and sometimes less. This
included shots that were handheld, tripod mounted and even using a remote shutter trip.

Later, I learned some information (totally new to me) that pointed out that if you were
shooting with the remote shutter trip with your head away from the viewfinder, stray light
could enter the viewfinder. This light would likely affect the camera's choice of auto
exposure, in AV or similar mode, by incorrectly setting it for a lower than proper exposure.

As a result of these all too frequent poorly exposed shots I began shooting more and more
in Manual Mode. (This was not foreign to me, having been using film SLR cameras from
the early 1950's in which Manual selection was all there was.) That is, I began setting the
aperture and shutter and ISO manually myself. Since digital is less wasteful than film, I
started taking several quick shots at different settings, then viewing them, and adjusting
as needed. But as stated above, viewing the shots on the LCD screen alone wasn't always
adequate. Eventually, I remembered there was the "Histogram option" in the Playback
Menu, where after taking each shot you can view the image plus its Histogram for up to 5
seconds. Being very familiar with the use of Histograms, from using Photo Shop7 for many
years, I finally realized - why not use the camera's Histogram to more thoroughly examine
each of the early test shots immediately. And choose from these, the exposure settings
giving the best overall results.

So, to conclude: My choice of controlling exposures, especially with the fabulous 180mm
lens, is to use Manual exclusively, arbitrarily pick an aperture, shutter speed, and ISO.
Then study the Histograms, and make adjustments to the Manual settings as appropriate.
Another variation is - use the camera's "digital preview" feature from page 171. This has
even 2 more advantages, it never gets recorded (thus doesn't need to be deleted later) and
it can be viewed on the LCD screen for up to 60 seconds instead of only 5 seconds for a shot.

[HGMonaro]

Another variation is - use the camera's "digital preview" feature from page 171. This has
even 2 more advantages, it never gets recorded (thus doesn't need to be deleted later) and
it can be viewed on the LCD screen for up to 60 seconds instead of only 5 seconds for a shot.

An alternative is to use the picture review function (who's official name I can't remember...) with the histogram displayed (when in picture review mode, press info until the histogram displays). This lets you take a shot and review the histogram. If you're happy, move on otherwise adjust camera, take another and repeat the process. You can also check the histogram of any previous pic you've got on the card.

[PDL]

Just use the little plastic viewfinder cover that came with the camera.

Blocks out the extra light that messes up the meter - that is why Pentax included it.

The Elitist - formerly known as PDL.

[jk333]

Is this really needed? Just posing a question. It seems to me that in the film era dead on exposures were a necessity. However, it appears to me that with post-processing and photoshop that exposures can be adjusted slightly now-adays.

I just think digital photos can be tweaked pretty easily in photoshop. As long as the exposure is close or reasonable...

[kevbirder]

Yes it is necessary. When recording on transparency film exact exposure is required. With negative film some correction can be made at the printing stage. With digital an even larger correction can be made and the big advantage is that you can do this yourself at little cost.

BUT... for best quality, 'correct' exposure is still necessary and in some cases needed for even average quality. For instance some of my shots of birds through long lenses using a K10D with auto exposure set, can result in a 2 stop overexposure. If you are photographing a white or very pale bird, the whole bird can be just a white blob where no amount of correction on the PC will help.

Underexposure gives more lattitude for correction, but the more correction, the worse the noise gets and there is still a limit where detail is completely lost. If I have to rush a shot I choose deliberate underexposure as I know that any blown highlights will be impossible to sort out, whereas to some extent underexposure can be corrected at a cost.