The tip of the eyedropper

As many of you know, I primarily shoot for JPEG output, and thus haven't yet gotten into the glories of working with raw files.

My recent work with white balance measurement tools has, however, gotten me slightly into fiddling with a couple of raw processing tools, namely PS/ACR and DPP.

One branch of this of course is the "make me white" eyedropper, a facility of both those programs.

Of interest is what is the size of the tip of the eyedropper - over how large an area of the image does it acquire pixels (and, if applicable, average their chromaticity).

The Help facility for my PS (CS2/v9.02) doesn't say anything about that.

The help facility for my DPP (v3.0.2.6) says it is a 1x1 px area.

Bummer!

Is this indeed the fact? Can this be changed? It would certainly seem that, for this purpose, some averaging would ordinarily be advisable.

I have been spoiled by my normal image editor (Picture Publisher 10) in which one can pick up the color over an user-"drawn" rectangular area (albeit not for raw WB correction purposes, since it only works with developed images).

Incidentally, the averaging there is by R/G/B values, not yielding a true average luminance or chromaticity if there is substantial difference in either over the sampling area.

Of interest is what is the size of the tip of the eyedropper - over how large an area of the image does it acquire pixels (and, if applicable, average their chromaticity).

Click to expand...

In ACR and LR, its based on the zoom ratio. 5x5 is the default, only until you zoom to 400% do you get a single pixel sampling. This is tied to the RGB readouts (that's what values they are providing).

Hi, Andrew,

Andrew Rodney said:

In ACR and LR, its based on the zoom ratio. 5x5 is the default, only until you zoom to 400% do you get a single pixel sampling.

Click to expand...

How lovely!

Thanks so much.

Now if only DPP could be so suave!

Best regards,

Doug

Correction, its always 5x5 according to Camera Raw with Photoshop CS3 (page 66 or 76 on Bruce's CS version):

The readout always reports the average of a five by five sample of SCREEN PIXELS. You can't sample individual pixels, thought you can get close at 400% zoom level. To sample fewer pixels, zoom in, to add to sample more pixels, zoom out.

Click to expand...

Jeff's addition reads:

It always reads 5-by-5 screen pixels at zoom levels of 100% or less, so it may give different values at different zoom levels. Wen you fit the entire image into Camera Raws preview, you're sampling an average of a fairly large number of pixels - the exact number depends on both the camera's native resolution and the size you've chosen from the Size menu in the Workflow controls. At zoom levels greater than 100%, the sample size is always 5x5 image pixels.

Click to expand...

Well, although in DPP 3.0.x the Help says that the eyedropper tip is 1x1 px, in 3.2.x (which I just installed) it says it is 5x5 px.

That's more like it.

But are those screen pixels or image pixels?

Best regards,

Doug

Hi, Andrew,

Well, it's nice that, as moderator, you can edit my post. But it is a little confusing!

But thanks for the additional info anyway!

Best regards,

Doug