JPEG & TIFF Saving from PS at Low Quality

[#1]

I have Milky Way shots taken on a Sony A7ii at f/2.8, 30 sec., 6400 ISO. I have them looking good in PS but when I merge layers and then save as a max quality JPEG or TIFF they look washed out, not even close to what's in PS. The image also seems to degrade in PS when I merge layers before saving. Another observation is that sometimes when I open the JPEG, the image opens at a higher quality for a split second and then reverts to the washed out state. My other images don't have this issue. I tried PS Support's suggestion to restore default preferences as well as reinstall PS but no luck. Why would the image look good in PS but degrade to such as degree when saving to these formats?

[#2]

I have Milky Way shots taken on a Sony A7ii at f/2.8, 30 sec., 6400 ISO. I have them looking good in PS but when I merge layers and then save as a max quality JPEG or TIFF they look washed out, not even close to what's in PS. The image also seems to degrade in PS when I merge layers before saving. Another observation is that sometimes when I open the JPEG, the image opens at a higher quality for a split second and then reverts to the washed out state. My other images don't have this issue. I tried PS Support's suggestion to restore default preferences as well as reinstall PS but no luck. Why would the image look good in PS but degrade to such as degree when saving to these formats?

[#3]

Are you comparing before and after merging at 100% zoom. It sounds like you are not. When zoomed out, the preview is blended using 8 bit softened layers. On most images that Alex little difference but with tiny points of light, like stars, the difference can be huge.

Always check your image at 100% before merging.

Dave

[#4]

Dave, thanks for this. Being a novice I want to make sure I understand your process. I tried merging and then zooming to 100% and printing the JPEG (the JPEG showed a zoomed out image). I also tried zooming then merging and printing. Both still gave me the washed out JPEG. Am I missing something or using the wrong sequence?

Thanks much,

Craig

[#5]

Neither will avoid the outcome. However zooming before merging will give you an accurate view of your blend which will be reflected when you merge.

So check and make any adjustments at 100% before you merge.

[#6]

If you still have an issue can you post a link to a PSD file unmerged and also a merged jpeg with the issue.

Dave

[#7]

Dave, thanks so much for looking at this issue. Here is a link to 2 PSDs with JPEGS saved at max quality. In each case when I merge all the layers to print I see degradation as well as in the saved JPEGS. In the Black Canyon  PSD I combined layers to be able to dodge & burn. But then I find that the combined layer is a degraded version of the original layer adjustments, so I have to move the orginal layers above the combined layers to retain the original adjustments. I hope this makes sense. Thanks again, Craig 

https://drive.google.com/drive/folders/1Mcn40YhmA-OJovAVt1VNrqpRL5j0K3Es?usp=sharing 

[#8]

"I have Milky Way shots taken on a Sony A7ii at f/2.8, 30 sec., 6400 ISO."

That's a textbook case. The point about 100% is that this represents one image pixel by exactly one screen pixel. It's the only way to view the pixel data accurately - and with a starry sky, you have a lot of individual pixels.

Any other zoom ratio resamples the image, and any resampling softens and blurs sharp pixel transitions.

What complicates this is that adjustment previews you see on screen are calculated from the screen image. That's done for performance reasons. If that screen image is a soft, resampled version, you get a lot of intermediate values that aren't really there in the original data. And the calculation is done on this false basis. So you get a misleading preview.

If you view the file at 100% when judging the effect of the adjustment, you don't get this misleading preview. You get a true representation of the pixel data and what the adjustment will do to them.

In other words - there's no degrading. You just got a false preview, because you didn't view at 100%.

In a normal photograph the effect is negligible and this isn't an issue. But with very noisy data, or "binary" images where pixels are either "on" or "off" (line art, halftone screen etc) - you always need to judge at 100%.

[#9]

Great explanation. Now I get it. Thanks so much.

[#10]

Hi

Thanks for those linked images it was useful to confirm the issue.

So, when viewed at 100% zoom there is no on screen difference between your start image, before or after merging and when viewing the jpeg in Photoshop. When zoomed out, there is a difference before and after merging.

That confirms the issue was as described above by myself and D.Fosse. You really must view before and after at 100% zoom. At less than 100% the image preview is not accurate as it is blended using combined and resampled pixels (at the screen zoom level) rather than the individual image pixels.

As an aside, I notice your jpeg is saved with the ProPhoto RGB profile embedded. That is fine for this comparison and for viewing on your own system and in colour managed applications. But if you ever post it on to the web  make sure you export, from the master PSD, a copy converted to sRGB.

Dave

[#11]

Again. great explanation. Important information to know as I get deeper into this. Many thanks.