CS3 merge to HDR, white point preview box?

Tango

can someone help me understand this?...:

after intial merging of expos in "Merge to HDR" tool, up comes a screen to preview and a "set white point preview" screen/box/slider bar.
(btw this is the point where i set for 16bit)

what should i do with this slider adjustment? leave it? move it to desired look in the preview? go to whiter preview?

??:dunno ??

pathfinder

bump

LiquidAir

Generally I set the white and black points based on the histogram. My goal is to set them as tight as possible without clipping to make sure I don't lose any of that dynamic range. Typically I try to get the brightness about right by adjusting the gamma but I but I don't spend too much time worrying about contrast until I have a 16 bit file.

Richard

AaronNelson wrote:

can someone help me understand this?...:

after intial merging of expos in "Merge to HDR" tool, up comes a screen to preview and a "set white point preview" screen/box/slider bar.
(btw this is the point where i set for 16bit)

what should i do with this slider adjustment? leave it? move it to desired look in the preview? go to whiter preview?

?? ??

I believe what you are referring to does not affect the final image, but only controls the appearance of the preview that CS creates. The tonal curve for the real image is determined by the options you select when you convert from 32 bits to 16 (or 8) bits.

Tango

thanks guys for the info,

LiquidAir, im setting WP & BP in ACR too each individual expo, this is something else or im not understanding you...btw, i havent see you around lately were ya been?

Richard, thanks and you maybe very right that it only affects the preview.

why thats an idea (as i hit my forehead)
i should attempt to do two seperete hdr's using the same raws and see what it does huh?

colourbox

I thought I had posted this reply yesterday, but this morning discovered I had posted in a completely unrelated thread (d'oh!)...:bash

Now I'm posting it here where it belongs.

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OK first of all I'm no HDR expert, but I have played with it in Photoshop. If you are specifically talking about the white point preview slider under the HDR histogram, that does not change anything within the file. This is not the same as the Levels white point!

The slider only controls the preview in the dialog box. Nothing more. The point of the preview is that it is impossible for your monitor to display the complete uncompressed range of tones represented by the HDR image, therefore this slider controls which "slice" of the total tonal range you are currently and accurately previewing on your monitor while you are selecting which images to include. All the tones above and below the range you are currently viewing appear clipped, but they are still in the file. They just don't fit on your monitor.

It is the same slider you find at the bottom of the merged HDR image so that you can preview how your 32-bit edits are affecting very dark and very light areas of the image.

You can test this by doing merges with that particular slider set to all kinds of positions, if I'm right it should have no effect on what comes out the other end.

If you actually want to change the white point of the HDR image, use the Exposure slider in the Image > Adjustments > Exposure command, or the conversion controls you get when you downsample to 16 or 8 bits.

Tango

thank you everyone.