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Author Topic: PS - image change on save or layer stamp.  (Read 5560 times)

ThirstyDursty

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PS - image change on save or layer stamp.
« on: July 22, 2015, 07:11:34 am »

So I worked up an image of the Milky Way in Photoshop. 7 image blend. Photoshop and Lightroom did not want to stitch.

Got it just the way I wanted...or as close as I could I'll with my skill.

Had a few layers set to "lighten" blend mode and high-pass on soft light and another on hard light with masks..and some hue/sat layers

When I stamped the visible layers...there was an obvious lightening and colour shift of specific sections of the image that aligned to these areas where I had blended in content. Same happened with saving, even without stamping.

Why? And how to get around this?


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ThirstyDursty

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Re: PS - image change on save or layer stamp.
« Reply #1 on: July 23, 2015, 06:30:14 am »

Really? No one has had this issue?


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D Fosse

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Re: PS - image change on save or layer stamp.
« Reply #2 on: July 23, 2015, 02:15:51 pm »

You have to view at 100% to get an accurate preview of adjustments. This is critical with grainy/noisy images (yours!), halftone screen, line drawings, etc. In short, anything that goes "on/off".

At any other ratio than 100%, the preview works on a cached/resampled/softened version with lots of intermediate values that aren't really there.

100% means one image pixel represented by exactly one screen pixel.
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ThirstyDursty

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Re: PS - image change on save or layer stamp.
« Reply #3 on: July 23, 2015, 07:17:23 pm »

Yes...you seem right...at 100% it doesn't seem to show any change.

100% is a very small portion of the photo.

Begs the question of which preview is correct? The stamped and saved option that shows lightening or the version prior to the stamp/save.

Ultimately the image is not going to be printed larger then 75cm-1m

I might have to print a small copy before I know.


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mdijb

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Re: PS - image change on save or layer stamp.
« Reply #4 on: July 24, 2015, 08:11:56 pm »

I had the same issue about 18 months ago and spent a lot of phone time with senior tech reps from Adobe.  I demonstrated the issue with them while they took over my machine.  The problem occurred intermittently and was very frustarting.

Here is the last correspondence they sent me

"I just wanted to let you know that I'm closing your case, but I can reopen it if need be at any time. I am sorry we couldn't determine the perfect resolution for you. I have let engineering know that although this is as designed, it's still a pain for customers. "


"Three engineers commented on this issue, all saying the same thing. Because of the way Photoshop redraws images that aren't at 100%, using reduced resolution versions of the image (the Cache Levels in Performance Preferences), fine color detail can be averaged out to a different color, especially when you zoom out. This is going to happen with all images, but especially on images with a lot of small areas of colors, like your fractal images. This is why it's as designed, and why it happens not all the time. "

Hope this provides some help or comfort

MDIJB
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ThirstyDursty

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Re: PS - image change on save or layer stamp.
« Reply #5 on: July 26, 2015, 07:46:40 am »

Hmmm. Comforting I guess ;)

High pass filters in lighten blend mode on Milky Way shots seem to cause this predictably for me.

Strange however that the none flatten image renders one way and the flattened one renders another. You'd expect any given zoom level to render the same....but no.

Now the question is how to predict the output...a few extra test prints I guess.


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D Fosse

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Re: PS - image change on save or layer stamp.
« Reply #6 on: July 26, 2015, 09:17:09 am »

How to predict the output is to view at 100%. That's all it takes.

All other zoom ratios are potentially inaccurate, for the reasons given above.
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ThirstyDursty

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Re: PS - image change on save or layer stamp.
« Reply #7 on: July 27, 2015, 01:03:35 am »


How to predict the output is to view at 100%. That's all it takes.

All other zoom ratios are potentially inaccurate, for the reasons given above.

not really helpful when your working on a large stitched document. Especially of star, or some form without hard lines and structure.

Not having the ability to view the changes your making across a large area makes it difficult.

Zooming in to 100% doesn't really let you know.

I'm looking at a bunch of dots that combined in massive numbers make a recognizable form. The Milky Way.

I could downsize the document which would probably allow it to render more accurately when zoomed out...but then I sacrifice the quality, I worked hard to capture.

It is only a few small spots...the global adjustments, I can just repeat till correct.

I'm trying to get the balance right and fix a few issues with stitching...zoom to 100% and you can't tell if it is right...because it is now out of context.

I found using the blending options to knock-out blending of the layer close to black and close to white...helped thin the stars/excessive noise...and made it merge very close to what it looked like.

Also...I'm my case it is the stamped layer that renders closely/same to 100%...the active layers are further....I found this out because there was a couple straight lines in the stamp, that appeared blended zoomed out.


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ThirstyDursty

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Re: PS - image change on save or layer stamp.
« Reply #8 on: July 29, 2015, 07:48:06 pm »

I the end. Because the file was so large. I found that a zoom of 33-50% provided accurate enough rendering....while still seeing enough of the photo to see changes in context.

Makes sense, rendering gets increasingly accurate as you zoom.

You may not need to be at 100% to be close enough ;)


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