Trevor.Dennis wrote:

 

there a[re] definitely times when flaterning the layer stack leads to unexpected results.  The workaround is to add a Copy Merged Layers layer to the top of the stack before flaterning.  (Shift Ctrl Alt e)

I'm wondering how...  Incomplete transparency all the way through, perhaps?  Bottom layer over transparency using something other than Normal blending?

Perhaps it would be good to get into specifics here...  What, exactly, does your Layers panel look like before the flatten operation, oslavens?

Ideally, could you crop a small part of your document and save it as a relatively small PSD file, then share it here?  We could use that to both try to reproduce the problem elsewhere, and (assuming we can) examine it to see what's up.  I know that with such an example in hand I could tell you why it's happening, as I'm sure could others here.

-Noel

I had the same problem six years ago and addressed it to the Forum and was told it was a problem with not viewing at 100%. However, when I made a print of the unflattenned and then the flattenned print, there were definite differences of loss of shadow details and other subtle differences which lead me to believe that there was a real difference in some images between unflattenned and flattenned. Try printing a flattenned and unflattenned version of the image.

Something to try, oslavens, is to create a 100% opaque white background layer at the very bottom (assuming you don't already have an opaque bottom layer), and see if the problem is alleviated when the image is flattened.

-Noel

oslavens, I don't see any images and files attached in any of your posts. If you can't examine and see an entire image intended for web usage at 100% zoom, then the question is what kind of screen are you using - it should very small in comparison ot the monitors of the intended web users. If you have an average size monitor and you can't see the entire image at 100% zoom then probably no one on the web will see it either unless the image is resized by the web program which naturally will remove detail information and can indeed loose contrast.

Images attached to emails are useless on this Forum. 

»If I raise the magnification to 100% and flatten there is no APPARENT CHANGE in contrast...«

Now you finally state it … it has been asked several time!

Views of other than Actual Pixels mean that Layer Masks and the other Layers are interpolated and therefore the result can differ.

You can post images on the Forum in the browser (with the camera icon), but not via email replies.

The previews are derived at from the interpolated elements (so for example a layer with only pure black and white may develop intermediate tones that are then affected by Adjustment Layers that dio not affect the actual pixels); any preview size other (at least bigger) than actual pixels can differ from the actual result therefore.

If the workflow has worked for you so far without noticing that it seems likely that this image differs significantly from the ones you usually edited.

I'm not sure what you mean by "preview".

When Photoshop displays the effect multiple (Adjustment) Layers have on each other it does not actually calculate a flattened resulting image in full res and downsamples that to the magnification you view at, but performs those operations with the resampled elements, so it is a preview.

Edit: The issue applies to Layer Masks and Layers alike.

Are you telling me that I should ignore the appearance of the flattened image and proceed to print?

Others and I are telling you that any preview other than Actual Pixels is not reliable, so what you think you have achieved you may not have achieved at all so long as you don’t see it at Actual Pixels-view.

There is a screenshot in my last post – please visit the Forum with your browser.

This is basically how you make images intended for viewing on the web.

First find out what is the average pixel count size of the monitors of your intended viewers. This is a link to a web site that can give you a clue for the general trends http://www.w3schools.com/browsers/browsers_display.asp and if you are interested in specific group and web sites you can use tools like this http://www.tastyplacement.com/monitor-size-statistics-for-web-design-html . After  you know the average pixel count size of the monitors of the intended viewers then you can decide how large as pixel count you want your images to appear in that space. You have to make this decision by viewing your images at 100% zoom. At 100% zoom one pixel of your image fits into one pixel of your monitor. When you zoom out less then 100%, a group of pixels from the image will be represented using their average color with one monitor pixel and this causes loss of detail and changed image appearance like the one you are experiencing. When you zoom in more than 100%, one pixel from the image will occupy a group of monitor's pixels and this will give enlarged pixel appearance (steps like effect) jaggies. Web browsers by default display images at 100%.  If your images are for a web site that is yet to be designed, and you are one of the design decision makers, create a new Photoshop document with a pixel count that is the average pixel count size of the monitors of your intended viewers and having in mind the other elements of the web page, decide the amount of space your images will be occupy in the overall design. If your images are going to appear on existing web site/s. Visit the site and make a screen capture of your screen, go back in Photoshop, choose to create a new document which automatically is set to the the pixel count of the content on your clipboard, and after that paste the screen capture. Then create or scale down your images to fit in the desired space. Again, the final effect will be what you view at 100% zoom. With all that said, have in mind that if your images are going to be posted on certain web site like this Adobe forum - images posted here are displayed in the messages as previews with certain size limit. Images larger than this limit will be scaled down automatically by the site but if you click on the preview image, it will show the full size as it appears at 100% zoom in Photoshop. You have to check how your images will be treated on the web sites you plan to use and then you can create them with the optimal pixel count size.

Another thing that you also have to be aware is that you don't have control over the physical size of your images because different monitors and display devices have different size pixels and this will make an image with the same pixel count displayed with the same zoom to appear at different physical sizes on the various monitor models and devices such as smart phones.

View the forum message on the web-version of the forum, to see the image indicating the camera icon’s location inline in the forum post.  If clicking on the link in your e-mail does something you’re not expecting then copy/paste or type-in the following link to the forum message:

http://forums.adobe.com/message/4349088#4349088