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Questions - CS2: Brightness and Exposure
Old 05-14-2007, 09:20 PM   #1 (permalink)
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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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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 02:15 AM   #2 (permalink)
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Quote:
Originally Posted by Stecyk View Post
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
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
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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 08:20 AM   #3 (permalink)
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Quote:
Originally Posted by R_Fredrick_Smith View Post
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.)
Hi RFS,

Thank you for your excellent detailed reply. I was hoping you would see my post and respond.

As I worked through your directions, I found in both cases I was moving to the right.

Exposure: Hit Alt, black screen, move to the right, until something lights up.

Shadows: Hit Alt, screen nearly all white, move to the right until black items in the shot show up as being black.

I understand your comments about brightness and contrast affecting the midtones.

Another follow-up question for you: When you are using the Photovision target, do you use the color samplers on the white and black strips? And if so, what values do you strive for?

On my example--

White: R:247, G:247, B:248 (seems good)

Black: R:65, G:63, B:63 (perhaps a bit bright?)

The black seems a bit bright. But if I increase the shadows, then I clip some of the darker areas, such as the perimeter of the target which is a deeper black.

I greatly appreciate your response.

Best regards,
Kevin
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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 11:13 AM   #4 (permalink)
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Which Photovision target do you have? The original or the new one shot version?
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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 12:00 PM   #5 (permalink)
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Which Photovision target do you have? The original or the new one shot version?
I bought it a couple months ago, and it is the 14" one shot version.

http://www.bhphotovideo.com/c/produc..._One_Shot.html
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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 04:42 PM   #6 (permalink)
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How are you liking that size? Do you think it is big enough, or would the 24 or 34 be better, especially if you use it as a reflector?
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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 05:47 PM   #7 (permalink)
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kgphoto,

I am just learning as I go here, so I am probably not the best person to provide an opinion. I have seen others comment that 14" was a good size.

In terms of a reflector, yes, 14" does seem small to me. I have other reflectors (see below), though, so my target's size doesn't worry me too much.

http://www.bhphotovideo.com/c/produc...lver_Gold.html

http://www.adorama.com/LSTGRGW.html?...grgw&item_no=1

I suspect RFS will provide some of his thoughts on the best sizes for the Photovision target.

Regards,
Kevin
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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 06:22 PM   #8 (permalink)
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Quote:
Originally Posted by Stecyk View Post
kgphoto,

I am just learning as I go here, so I am probably not the best person to provide an opinion. I have seen others comment that 14" was a good size.

In terms of a reflector, yes, 14" does seem small to me. I have other reflectors (see below), though, so my target's size doesn't worry me too much.

http://www.bhphotovideo.com/c/produc...lver_Gold.html

http://www.adorama.com/LSTGRGW.html?...grgw&item_no=1

I suspect RFS will provide some of his thoughts on the best sizes for the Photovision target.

Regards,
Kevin
My first target was the 34" one. I found it a bit large for the kinds of things I did. I sometimes do product shots in a 3' x 3' x 3' light tent and it was very hard to use the 34" target in that, for example.

Yes, it did make a good reflector, but I have other fold up reflectors that are much more suitable for reflecting type tasks. I wanted a target that I could carry around in my back pocket and the 14" size was ideal for that.

The later targets are even better than the earlier ones because they have a focus target on the B/G/W side.

I do use the 14" target as a reflector for head shots. I have the model hold it under her chin just out of sight of the viewfinder which bounces some light back up under eyes, hairline, etc.

Cheers,
rfs
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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 06:30 PM   #9 (permalink)
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Quote:
Originally Posted by Stecyk View Post
Hi RFS,

Thank you for your excellent detailed reply. I was hoping you would see my post and respond.

As I worked through your directions, I found in both cases I was moving to the right.

Exposure: Hit Alt, black screen, move to the right, until something lights up.

Shadows: Hit Alt, screen nearly all white, move to the right until black items in the shot show up as being black.

I understand your comments about brightness and contrast affecting the midtones.

Another follow-up question for you: When you are using the Photovision target, do you use the color samplers on the white and black strips? And if so, what values do you strive for?

On my example--

White: R:247, G:247, B:248 (seems good)

Black: R:65, G:63, B:63 (perhaps a bit bright?)

The black seems a bit bright. But if I increase the shadows, then I clip some of the darker areas, such as the perimeter of the target which is a deeper black.

I greatly appreciate your response.

Best regards,
Kevin
First, keep in mind in regard the Shadow slider that anything that shows up while you are holding the Alt key will be completely black in the photo if you use that shadow. So you are often deciding what you want to be completely black in the photo and you slide until that item just shows up. Now anything that is darker than that item will be totally black also. Take particular care when dealing with eyes. If you see part of the eye show up (other that the pupil), then back off to the left because usually you don't won't any part of the eye other than the pupil to be totally black.

When using the target in post processing, there are two approaches. If in RAW, then you can click on the gray stripe to set the color balance. I then usually slide a little right at that point to get extra warmth. But I usually try to get the WB right in the camera, so I don't usually have to do much in the RAW converter.

If using the target in Photoshop, then you will use it in Curves to set the color balance. You do this by clicking first on the black stripe with the black eye dropper, then the white stripe with the white eyedropper and finally the gray stripe with the gray eyedropper. This usually gets you very close. But before you do this, you need to set the defaults for eyedropper use in the Curves palette. I use about 20,20,20 for black and 240,240,240 for white. and I set gray to 128,128,128 (18% gray).

Cheers,
rfs
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Re: Questions - CS2: Brightness and Exposure
Old 05-15-2007, 09:20 PM   #10 (permalink)
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Quote:
Originally Posted by R_Fredrick_Smith View Post
First, keep in mind in regard the Shadow slider that anything that shows up while you are holding the Alt key will be completely black in the photo if you use that shadow. So you are often deciding what you want to be completely black in the photo and you slide until that item just shows up. Now anything that is darker than that item will be totally black also. Take particular care when dealing with eyes. If you see part of the eye show up (other that the pupil), then back off to the left because usually you don't won't any part of the eye other than the pupil to be totally black.

When using the target in post processing, there are two approaches. If in RAW, then you can click on the gray stripe to set the color balance. I then usually slide a little right at that point to get extra warmth. But I usually try to get the WB right in the camera, so I don't usually have to do much in the RAW converter.

If using the target in Photoshop, then you will use it in Curves to set the color balance. You do this by clicking first on the black stripe with the black eye dropper, then the white stripe with the white eyedropper and finally the gray stripe with the gray eyedropper. This usually gets you very close. But before you do this, you need to set the defaults for eyedropper use in the Curves palette. I use about 20,20,20 for black and 240,240,240 for white. and I set gray to 128,128,128 (18% gray).
Thank you, once again, for your terrific reply.

I understood what you've written and will put that knowledge into practice.

Best regards,
Kevin
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