Quote:
Originally Posted by Stecyk
Hi,
I have a few questions relating to my Photovision Target, light meter, Adobe ACR (CS2), and B&W UV filter.
Tonight I checked to see how accurate my light meter and camera (Canon 20D) combination are. I took several pictures of the target, using the settings from the light meter, with and without the UV filter on.
I discovered that the UV filter has almost no affect upon the exposure. That is, when I compare the histograms for the filter on and the filter off using the same manual settings, the histograms are almost indistinguishable. That's good.
I also discovered that my light meter and camera combination seem to be aligned. I can use my light meter settings without having to factor in a calibration factor.
My question concerns Adobe's ACR. When I open the RAW files, I notice that the "brightness" is automatically set at +50. The histogram from the brightness setting at +50 corresponds well to my camera's histogram. If I reduce the brightness to 0, then the histogram is markedly different from that of my camera's. Am I correct to assume that +50 is a default setting?
Continuing on with the brightness setting, how does the Brightness setting differ from the Exposure setting? One oddity that I noticed is that when I increased the brightness and pushed the histogram off scale to the right (too bright), I didn't get the blown out highlights. I have the "Preview", "Shadows", and "Highlights" boxes all checked. However, when I increased the exposure, I blew out the highlight easily. I am curious as to the major difference between Brightness and Exposure settings and how they should be used.
I would appreciate your thoughts on my questions.
Regards,
Kevin
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The exposure slider sets the white point for the photo. The shadows slider sets the black point. You would normally set these two first before playing with color balance. The easiest way to use them is hold down the Alt key while using the Exposure and Shadows slider. When you first slide the exposure slider the image will turn totally black (or maybe not). If it is black then nothing is being clipped at this point. Start sliding left till something non black starts to display. This will be something white or lighter in the image. What ever shows up will now be pure white in the image no matter what color it is. So back off till there is no white and you now have the optimum exposure. On the other hand, say you're shooting on a white background and you want it pure white, then you could slide until you see details of the subject start to appear, then backoff leaving the subject black. The white point is now set. Now repeat with the Shadow slider except move right slightly. If everything is white, then move back left until something starts to show up. What every shows up will be the darkest part of the photo. You are now choosing the point that you want black, so keep sliding till whatever you want to be the black point can be seen. Ultimately these two steps take a little practice but essentially the same thing you do with the set black and white points while setting up curves.
Now adjust the brightness and contrast sliders which primarily deals with the midtones. Now adjust the white balance.
The Auto settings are usally based on what camera you use. You can calibrate anyway you want using the last tab in CS2 where you make adjustments depending on what you want as your default Auto position. Myself, I just turn Auto off and always go thru the slider sequence above.
CS3 adds several more sliders and tabs including a highlight recovery slider, a fill slider, etc.
Just remember that Exposure/Shadows control the white and black points (the highlight and shadow details and brightness controls the midtones.)
Cheers,
rfs