Re: [APML] Histograms

[Jerry Lodriguss <jml@astropix.com>]

>Once you've finished the above levels adjustment you can switch to 8-bit 
>mode without significant loss. If you use layers for further adjustments 
>(e.g. curves, hue/sat, etc), you probably won't see the "picket fence" again.

Hi Matt,

Whether you see the picket fence again will depend on how much further the 
data is manipulated. If it's manipulated too much, you'll get the fence 
again even if you use adjustment layers when you flatten the image.  Using 
adjustment layers has absolutely nothing to do with it!

There is nothing magic about adjustment layers that protects the image from 
data loss.  You can preserve the original data just as well by archiving 
the original and working on a copy.

That said, I certainly won't argue that adjustment layers are not a very 
nice feature for convenience and playing around with corrections.

The one true advantage to adjustment layers, which you did not point out, 
is that if you use multiple adjustment layers with changes that cancel each 
other out, the changes are not made, whereas if they were done sequentially 
without adjustment layers, the data would be lost immediately. But this 
data would not be lost anyway if the operator knows what they are doing.

Adjustment layers only minimize data loss in the sense that they help the 
operator from being a bone-head <G>, but they will not prevent data loss.

For someone who is not that experienced, if they are going to keep making 
change after change, adjustment layers can be a good tool while learning.


>I believe that certain members of this list are over-enamoured with 16-bit 
>processing.


Well, there is no way you can argue that if you can do a correction in 16 
bits that it is not better doing it there than in 8 bits.  (my goodness, 
that certainly was a convoluted sentence! <G>)

Having said that, I have never worked in 16 bits because I never had access 
to a scanner that would give me 16 bit data. If I could do it all over (and 
who doesn't wish they could do everything over! <G>), and re-scan 
everything, I certainly would do it in 16 bits.



>  I contend that one does not experience material loss in 8-bit mode, as 
> long as you know how to configure the histogram correctly before 
> switching into 8-bit mode and as long as you use layers.


If the histogram is correctly configured in 16 bits, then most of the work 
is done before it is converted to 8 bits. <G>

But again, adjustment layers has nothing to do with it.



>I'd be willing to share the raw data with anyone who wants to try to 
>process that image, and especially to anyone who believes they can succeed 
>without layers.



Anything you can do with adjustment layers, you can do without them... if 
you know what you are doing. <G>

At least some of us have succeeded without them, I've never used them.

I would certainly recommend them to anyone who is just learning.


Jerry



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