Waldemar
Enthusiast
Feb 9, 2005, 8:45 PM
Post #4 of 4
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Re: [Danlson] Best match for GL2?
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I had two good teachers on exposure. One was a wizard of a photographer of the old school who insisted i memorize, memorize, memorize. I wasn't a star pupil, but I never forgot that. The other a wonderful text on photography printed in the early 70's in the UK. Sadly, I no longer have the book and can't remember the title. However, a browse through the photography section of a good used book store should yield a wealth of titles. in the meantime, here is a brief commentary I had writtn a few days ago on another forum. Hope it helps.
"There are two reasons for choosing an f-stop in the mid range of the aperture scale. First, lenses (any kind of lens) will have the best edge to edge sharpness at the middle of the scale. Second, the depth of field is still relatively shallow, which allows the subject in focus more attention. It "pops" out of the image, as it were. F4.0 is ot quite mid point. Rather like 40% of optimal sharpness, with optimal being 50%.
Aperture is a mathematical relationship between the diameter of the lens and its focal length at the plane where the lens iris is located. An f2.0 aperture on a fixed 50mm lens means the diameter of the iris is 25mm. With the same focal length, an f4.0 is 12.5 mm, etc. Each full stop change represents (depending upon the direction) either a reduction in aperture diameter by one-half or a doubling of the diameter. The maximum diameter is the "speed" of the lens or, how much light passes through it. The very best lenses have a "speed" of less than 1.0.
A zoom lens, by design, allows you to change the focal length. Changing focal length automatically changes the aperture setting. That is why lenses list their apertures as a range, as in f3.5-5.6. Most video lenses rate a speed of 1.6 at the widest angle, and as low as 5.6 at the extreme telephoto position.
OK, as fascinating or boring as that information may be, it is only support knowledge to exposure. Exposure is based upon delivering just enough light to the film/CCD chip to represent a balance between pure white and pure black that produces an image that looks very much like what you would expect to see. Ideally, setting an exposure exactly between black and white should produce the image you expect to see. In fact, it is only the subject within the frame, not the bakground, that needs this mid-point exposure as a starting point. Under-exposing that subject intensifies color saturation and contrast. Over-exposing softens and brightens everything. Movement in either direction will shift the mood of the image. So, what is the exposure that gives you the image you want to see?
There is really no right or wrong in exposure, just missing the mark by a little or a lot. The easiest thing to do is to find what looks right. The process that gives the greatest rewards is to learn all of the elements of exposure (I've only touched upon the subject), and then CHOOSE what looks right."
G5 1.8. Final Cut/QT Pro/iMovie/Still Life. GL1. XL1-s
(This post was edited by Waldemar on Feb 9, 2005, 9:28 PM)
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