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Forum: Photographic Technique
07-07-2019, 06:11 AM
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The K-1 spotmeter is relatively narrow and is defined by the circle in the center of the focusing screen. The K-1's spot has a diameter about 1/6th the height or 1/9th the width of the frame. In angular terms, the K-1's spot depends on the focal length. A K-1 with about a 200 or 250mm lens matches the 1° spot of the Pentax Spotmeter. So you could mount a telephoto lens, use the spot meter & green button in M mode to pick the exposure, then swap to the lens you want to use for the shot. (Note, if the K-1 is set to link the metering spot to the AF spot, the size of the spot depends on the AF zone size and moves with the AF point.)
P.S. You can map the sensitivity pattern of any TTL meter and AE mode by putting on a wide-angle lens, pointing the camera at a bare bulb or bright light source in an otherwise dark scene, and then panning the camera while watching the meter reading slide up and down.
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Forum: Photographic Technique
04-05-2019, 03:22 PM
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There may be no "right" exposure setting but there sure are a lot of wrong ones.
With at least 19 stops available in shutter time (1/8000 sec to 30 seconds), at least 7 stops typically available in aperture (f/2.8 to f/22), and least 10 usable stops in ISO (100 to 51200), the total LV range of the K-1 is at least 36 stops. But the DR of the K-1 is only about 14 stops which means the majority of possible exposure settings are grossly over-exposed or under-exposed.
For most evenly-lit scenes, the dynamic range of the scene is much smaller than the 14 stops of the sensor. Maybe a stop of over-exposure and maybe several stops underexposure can be corrected in post with no problems. Metering can be a little sloppy. If the scene has high DR and the photographer isn't willing or able to use multi-shot HDR techniques, then getting the exposure right does matter. And if the goal is a well-exposed SOOC image, then an "accurate" exposure is important.
An "accurate" exposure means finding an exposure that doesn't clip the highlights you want to keep, doesn't lose the shadows you want to reveal, and records each gray level in the scene as the gray level you want in the final image (e.g., the white paper looks white, the black cat looks black, etc.)
Metering is the first step to avoiding wrong exposures or getting toward right exposures. The different metering methods differ in how they get to a "good" exposure. None of the metering modes gets the right exposure 100% of the time. What's interesting is that some metering modes are more predictable than others in how they react to the scene which lets the photographer be more confident that they can depend on the reading. However, predictability brings a curse -- the predictable metering modes are dumb.
Spot metering has both the dumbest and the most predictable behavior. It's easy to meter a spot in the scene, know that the spot is something other than 12.5% gray, and know that some ħEV compensation with get the gray of that metered spot to be the desired gray level in the final image. Spot metering takes more work but it can lead to much more precise exposure settings.
Center-weighted is also pretty dumb but predicting it's behavior on a high-dynamic range scene is a little harder. Is the large dark mass of the foreground going to cause underexposure? Is the big of puffy white cloud or sun at the top of the frame going to cause overexposure? It can be hard to tell and make a good EV compensation choice.
Matrix is the least dumb, usually the most accurate, but also the most unpredictable. It's even less obvious whether a matrix reading has already compensated for unusual darkness or brightness in the scene. For most scenes, matrix is good enough but for some scenes it's not good at all.
Next comes EV compensation to correct for the discrepancy between the metered exposure and a better or more correct exposure. There are three primary reasons for using EV compensation:
1) the scene is fooling the meter or is NOT the 12.5% gray (e.g., the proverbial white cat on a white chair in a snow field)
2) the photographer wants to ensure no detail is lost at one extreme of the light level range (under-exposing to protect highlights or over-exposing to capture deep shadow detail)
3) the photographer does not want the typical "accurate" exposure (e.g., high key and low key)
One mode you haven't mentioned is using manual exposure, spot metering, and the green button. It's a really powerful combination because with the spot meter live in M mode, the exposure bar graph dynamically shows the discrepancy between the current exposure setting and the LV in the current spot location. So you point the spot at some "gray" part of the scene, hit the green button, adjust the exposure manually until it's over- or under-exposed to suit how overly white or over black the spot was. Now, if you move the spot across the scene, you get a dynamic reading can see if some part of the scene will clip or be too dark.
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