LR2 and Mogrify Watermarking effecting JPEG quality

[tenderoni_tony]

Hey all!

Loving the forum, and Lightroom. My question/problem is that when I run mogrify to add a graphical watermark and file: export to JPEG (not through the print utility), I see a slight but noticeable difference in the quality of the jpeg. I'm curious if anyone else has seen this, or if I am doing something wrong in my process.

Here are the details:

OS x 1'.5.6
LR2 2.3
Camera Raw 5.3 (part of LR2)
Mogrify 1.63
Original photos: Nikon RAW
Export to JPEG, image quality 7'
Graphical Watermark: transparent PNG, overlay mode: normal
Sharpen for screen: low
settings: JPEG: 7' Quality: sRGB
Image size: 96 ppi/ resize to 48'x48' (width or height)
Output sharpeing: screen, low
Post: nothing

When mogrify is used:
Mogrify config: (checked) Use LR2/Mogrify's built in version of Image Magik (recommened) - I know this is suppsoed to be only for Windows, but if I do not check that box I cannot export without "setting a path to a Mogrify application."
Mogrify Graphical WM: Overlay watermark, no resize, overlay mode: normal.

The problem: simply there is pixelation on the Mogrify shot. Notice the watermark itself is pixelated. Look closely at the leg of the wrestler in red, where the red signlet and his leg meet that line is pixelated.

The reason these are are saved out at qual 7', is they go up with about 5' other shots per page (then maybe 1' pags), so 7' is the sweet spot between image size and quality.

I'm curious what Mogrify is doing to get the watermark on the jpegs and why the quality of the image would drop a bit.

Interestingly, if I do not even add the watermark (say it isn't directed to a file) the image that comes out through Mogrify has less quality.

I'm attaching two test shots.

Thanks!

 

[Mark Sirota]

Welcome to Lightroom Forums.

I think what that is JPEG artifacts from double-compression. You're handing Mogrify a 7'-quality JPEG, and then asking it to resave it as a 7'-quality JPEG. If you set Lightroom to export at 1'' and then Mogrify at 7', that should go away.

 

[tenderoni_tony]

Hey thanks Mark! That actually sounds like what's happening. Question is, where in Mogrify do I have it save out at qual 7'? Would I turn off resizing in the LR File Settings area and turn on Mogrify's resize? I do not see an image quality setting there (but do see a list of resizing algorithms that look intresting).

Thanks again!

 

[Mark Sirota]

Huh. I guess I was remembering something else -- I thought LR2/Mogrify allowed for changing file formats and specifying JPEG compression and all that. In fact, I thought I remembered advice to export to Mogrify as TIFF, then having Mogrify save as JPEG.

But I don't see that option now. I apologize for the confusion.

As a test, if you set the quality in the Lightroom export to 1'', does the effect go away? If so, this is still the angle to pursue, and I'd suggest asking Tim Armes. If not, we'll bark up another tree.

 

[tenderoni_tony]

When LR file settings is set to quality 1'' there seems to be no discernible difference between the files. The file, however, is 265kb (too big). At 85% I start to see a difference, file size is 1''kb.

I appreciate your time Mark. I know Tim is on this forum, maybe he will chime in (I've sent him a personal email, but I'm sure he's a busy guy.)

 

[stasber]

I've stopped using Mogrify for the same/similar reason, until I can suss out if there's some technique I need to master to get round this.

It was getting a bit annoying, though not tried it in a while. The only thing switched on in Mogrify was the watermarking - and nothing else - and the change in the jpg quality was noticeable, I've no idea why [meaning I gather something along the lines of what Mark suggests but it "shouldn't" affect final quality].

I'm not going to have time to experiment with it again, just registering my interest fwiw.

 

[tenderoni_tony]

Solution from Tim

Hey all,

So, Tim got back to me about this and the quick answer is: The mogrify compression ratio is different to that of Lightroom, so you need to increase the quality slider.

The longer answer based on my further query is:

-----------

Thanks Tim! And to be clear, increase the quality slider on the LR
File Settings pane, right?​

Yes.

Not sure if you saw, but someone suggested
the files were getting double compressed, is that happening - LR
compresses then Mogrify compresses?​

Mogrify export a JPEG at 1''% quality, works on that, then compressed using mogrify and the value that you choose using the slider.


So, technically that's true, but in practice a 1''% JPEG is so close to the original that it's totally imperceptible. If you're interested, export a TIFF and a 1''% JPEG, put each into a layer in Photoshop and put the top layer into difference mode...

--------

So, it sounds like for me it's back to finding that sweet spot between file size and image quality. I'm not sure why Mogrify doesn't have an export as JPEG setting, but that's a different thread.

Good luck all!