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moire on the net

GlennH 12 1.9k 1 France
28 Nov 2012 7:47PM

Quote:Hi Gareth...i did beef it up a bit to show whats going on, can you see a green and purple rainbow effect on the inner edge of the Vignette ???

I'm in need of a new monitor myself, but I think you're describing banding - which will often be revealed if you create artificially smooth gradients in a photo. It helps if you don't over-calibrate your monitor, but it's not unusual for a consumer-level monitor to exhibit a little banding. I can see your rainbow (!), rather worryingly, but then I'm already aware of some degree of banding in my display - most of the time it has no effect.

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User_Removed 8 4.6k 1 Scotland
29 Nov 2012 10:20AM
If moire was present, you would be most likely to see it on areas with a sharp texture - like woven clothing fabrics. It's not something you would expect to see in an area of sky.

Before you spend £500 on a decent monitor, ask yourself this question:

When you say you don't see the problem in Lightroom but you do on uploads, are you viewing both versions on the same monitor?

If so, the problem is not with the monitor but with the processing and the subsequent treatment by the site/software that you are uploading to/opening on.

I suspect.

Also, check that your Lightroom "export" settings are compatible with your intended use of the exported file. For example, if you are exporting as a Jpeg for upload to a website, export it as the size that the website will accept. That way the website does not have to process your image to reduce its size. (By "size" I mean the actual pixel dimensions of the image, not the ppi.)

thewilliam 9 6.1k
29 Nov 2012 10:39AM
We get quite bad moiré on denim in our studio selling software where the resolution of the images has been much reduced for speed of loading and occasionally in PS at magnifications less than 100%.

I imagine that some web viewers aren't viewing at 100%.
GlennH 12 1.9k 1 France
29 Nov 2012 10:50AM
This isn't moiré; it's banding, although if it's not visible to everyone then it would appear to be local and monitor-related. You can induce it (if your monitor is of sufficiently poor quality or poorly calibrated!) by creating an extremely smooth gradient, as is effectively being done here with the vignetting.
mikehit 8 8.0k 13 United Kingdom
29 Nov 2012 10:54AM
Good comment, LF
Also, LRr has a moire correction tool so you can try this - if it is moire then it will be reduced.
GlennH 12 1.9k 1 France
29 Nov 2012 11:50AM
Painful though it is (on the wallet that is), I suspect Vince might have been right with the new monitor idea. On the other hand two or three others can see the banding - perhaps we're the poor Dell owners?
GlennH 12 1.9k 1 France
6 Dec 2012 11:32AM
This thread has proved beyond much doubt to me that I'm currently running a poor monitor profile! Sad

You know something's not quite right when a photo looks better in Opera.
CDSINUK 5 223 England
9 Dec 2012 10:42AM

Quote:Painful though it is (on the wallet that is), I suspect Vince might have been right with the new monitor idea. On the other hand two or three others can see the banding - perhaps we're the poor Dell owners?

or indeed Packard Bell Smile
GlennH 12 1.9k 1 France
9 Dec 2012 12:39PM
If it helps any - I was probably seeing your picture in a worse state than anyone else because my monitor profile was poor. That's the only conclusion I can reach when I open the same page in Opera and it loses a lot of its banding - Opera doesn't use the monitor profile (in fact that's how you're meant to test the bare calibration settings - minus the profile).

Skipping my monitor altogether and viewing your photo on an Eizo - it still exhibits some degree of banding/posterisation, which has come about through intense lossy processing and/or JPEG compression, but use of artificial gradients in a photo (i.e. vignetting in this case) increases the probability of it happening many-fold. There isn't enough info in your web photo to render the gradient smoothly.
CDSINUK 5 223 England
10 Dec 2012 8:24AM
thanks Glen, i would assume this would be more pronounced in a crop situation where a lot of the information is lost ? it does seem worse in cropped photos ?
GlennH 12 1.9k 1 France
10 Dec 2012 9:59AM
Well firstly, I see no evidence of moiré problems in this picture. That's a 'false colour' problem that tends to occur when you have intricate patterns in a photo; they might be criss-crossing patterns or just closely positioned linear details, e.g. venetian blinds, shutters, fencing. That particular problem is more prevalent with very sharp lenses and in cameras with no anti-aliasing filter. See here. I encounter it occasionally and use Lightroom v4 to deal with it.

As far as your picture goes I'm seeing an oval-shaped banding (posterisation) that mirrors your vignetting effect. The vignetting is the initial cause of the banding because it's a test of both image quality and monitor quality. Essentially you need enough data in the image file and your monitor image to represent the transition in tone smoothly. Over-calibration of a monitor can cause banding problems (or a poor profile...). If you're filled with curiosity you could try this gradient test. Ideally it needs to be done in a browser that doesn't use a monitor profile - IE or Opera.

Editing a file in 8-bit mode loses significant chunks of data, as does compressing a file heavily as a JPEG. If you repeatedly edit and save a JPEG the problem is exasperated. In Lightroom you won't see the problem because at that point the photo—or representation of it—contains enough data to avoid posterisation. I wonder if you're producing these web photos from raw, or if you're using LR to edit JPEGs?

The other issue here is the halo around the bird, which appears to be artefact caused by over-sharpening or an unsubtle selection method. I don't think that's the problem you're describing, however! Cropping a photo magnifies some unwanted properties, such as noise, but it's more likely to be the treatment of the photo prior to resizing for web that's caused these particular problems.

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