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Help Finding Dust Spots And Grain  
User currently offlineyowgangsta From Brazil, joined Feb 2005, 31 posts, RR: 0
Posted (1 year 8 months 1 week 14 hours ago) and read 5664 times:

Over the last year and more recently, I've had several photos rejected for dirty (dustspots) or grain. Things that should be obvious for me before submitting, but for whatever reason I don't see it. Maybe it's a poor monitor calibration or poor monitor altogether.

To clarify, I'm using the healing brush to remove dustspots that I find after equalizing the image, but the artefacts that are left behind are causing the rejections. Here's a couple of examples:
http://www.airliners.net/procphotos/...1365986031.3321acds_0083pr-mbj.jpg
http://www.airliners.net/addphotos/r...1365876690.6292acds_9971cc-cxg.jpg
http://www.airliners.net/addphotos/r...1365730225.7958acds_0166pr-gte.jpg

Maybe it's obvious to others, but I've even had to rework my workflow to do a smart blur to get rid of subtle grain that I don't see. Without that, I'd have a bunch more rejections for grain in dark areas including the sky.

I'm currently using a Viewsonic monitor (http://www.viewsonic.com/us/monitors/vx2453mh-led.html). Dynamic contrast ratio at 30,000,000:1

Curious if anyone can point me to some calibration technics that could help make dust spots and grain a bit more visible. Also would like to know what type of monitor characteristics I should look for the next time I buy one.

Cheers.

[Edited 2013-04-25 06:57:13]

10 replies: All unread, jump to last
 
User currently offlinevikkyvik From United States of America, joined Jul 2003, 10356 posts, RR: 26
Reply 1, posted (1 year 8 months 1 week 13 hours ago) and read 5643 times:

Quoting yowgangsta (Thread starter):
Things that should be obvious for me before submitting

They're not always obvious. Can be tough to pick out sometimes.

Quoting yowgangsta (Thread starter):
Curious if anyone can point me to some calibration technics that could help make dust spots and grain a bit more visible

If you're using Photoshop, equalize the image. That will (usually) make dust spots easier to see, and frequently grain, as well. Or, dragging the image around the screen (in circles, or left to right, or whatever) tends to make dust spots and grain much easier to pick out.



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User currently offlineyowgangsta From Brazil, joined Feb 2005, 31 posts, RR: 0
Reply 2, posted (1 year 8 months 1 week 12 hours ago) and read 5629 times:

Thanks for the response. I do equalize during the dust spot removal. I think part of what creates the problem is the remnants of the healing brush. I just thought those remnants were neglible.

Recently I've adopted cloning with a gradient brush that's giving better results, but it still leaves me with grain in my photos that I need to remove with a smart blur.

Considering my work flow involves level, resize, USM, smart blur, I'm not sure how this grain is polluting my pictures as much as it is when not using the smart blur.


User currently offlinevikkyvik From United States of America, joined Jul 2003, 10356 posts, RR: 26
Reply 3, posted (1 year 8 months 1 week 11 hours ago) and read 5620 times:

Quoting yowgangsta (Reply 2):
I think part of what creates the problem is the remnants of the healing brush. I just thought those remnants were neglible.

I find the clone tool tends to work more consistently, since you can pick a region of sky to use to clone out the dust spot. Spot healing tool sometimes works, but sometimes leaves remnants that can be as bad, if not worse, than the original dust spot.

For grain, you might try using some noise reduction on the full-size image, prior to resizing. Of course you can also use NR after resizing, but I'd do it selectively, only on the parts of the photo that need it. I'd be careful using a blur or median tool - the photo could end up with banding or blotchiness, instead of grain.

With that said, obviously the better the exposure, contrast, and sharpness straight out of the camera, the less noise you'll introduce in editing.



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User currently offlinemoose135 From United States of America, joined Oct 2004, 2409 posts, RR: 10
Reply 4, posted (1 year 8 months 1 week 11 hours ago) and read 5616 times:

Quoting vikkyvik (Reply 1):
Or, dragging the image around the screen (in circles, or left to right, or whatever) tends to make dust spots and grain much easier to pick out.

I've tried that technique a couple of times. All I get is dizzy...

Quoting vikkyvik (Reply 3):
I find the clone tool tends to work more consistently, since you can pick a region of sky to use to clone out the dust spot. Spot healing tool sometimes works, but sometimes leaves remnants that can be as bad, if not worse, than the original dust spot.

I'll usually use the clone tool, but if I end up with a bit of an edge where I've cloned (looking at the equlized image) I'll give it a little touch up with the healing brush.



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User currently offlineyowgangsta From Brazil, joined Feb 2005, 31 posts, RR: 0
Reply 5, posted (1 year 8 months 1 week 3 hours ago) and read 5563 times:

Quoting vikkyvik (Reply 3):
Spot healing tool sometimes works, but sometimes leaves remnants that can be as bad, if not worse,

I believe that's what's happening to me.

Quoting moose135 (Reply 4):
I'll usually use the clone tool, but if I end up with a bit of an edge where I've cloned

I think I'll go back to cloning but with a gradient brush, to avoid the harsh transition of where the cloning took place.

Quoting vikkyvik (Reply 3):
For grain, you might try using some noise reduction on the full-size image, prior to resizing.

I never understood the parameters for NR in PS. What do you recommend?


User currently offlinevikkyvik From United States of America, joined Jul 2003, 10356 posts, RR: 26
Reply 6, posted (1 year 8 months 1 week ago) and read 5546 times:

Quoting yowgangsta (Reply 5):
I think I'll go back to cloning but with a gradient brush, to avoid the harsh transition of where the cloning took place.

Yes, use a brush with a soft edge rather than hard edge, if that's what you mean. Also, I tend to set the opacity at 80%. That's usually plenty to eliminate visible dust spots, and helps not have as big a transition.

But really, the key is picking a part of the sky for the clone source that matches the area you're cloning over.

Quoting yowgangsta (Reply 5):
I never understood the parameters for NR in PS. What do you recommend?

Well, for NR on the full-size image, which I don't do selectively, I do it on the RAW image. Parameters vary quite a bit depending on the amount of noise in the photo.

For selective NR on the resized JPEG, it's almost always:
strength: 1
preserve details: 0
reduce color noise: 30%
sharpen details: 0

...and it's only applied sparingly to noisy areas, if I feel it's necessary.



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User currently offlineJKPhotos From Germany, joined Nov 2011, 339 posts, RR: 0
Reply 7, posted (1 year 8 months 6 days 15 hours ago) and read 5506 times:

Hi,

concerning the nois reduction I would recommend a plug-in for PS.

I tried PS own version before, but it did not work out too well for me.
Now I am using the "dfine noise reduction" and it works perfectly.

There is a trial version if you want to try it.

Cheers.


User currently offlineThumper45 From Canada, joined May 2013, 4 posts, RR: 0
Reply 8, posted (1 year 7 months 3 weeks 2 days 5 hours ago) and read 5248 times:

For an image like that there should be no apparent noise unless the equipment is out of date or the settings are wrong.

Shoot as low ISO as you can go, even if that means you shoot for an underexposed image and have to bump the exposure up in PS (shoot in RAW format if you underexpose, it gives you far more margin to adjust the exposure without loosing quality).

As for dust/dirt, the easiest thing to do is take your camera in to get it cleaned. If you are like me ever minute you spend editing is lost time for shooting and making money. $20-50 ever 3-6 months to have the camera professionally cleaned (or you can give it a go yourself if you want to) is well worth it and saves you the hassle of having to edit out junk.


User currently offlinevikkyvik From United States of America, joined Jul 2003, 10356 posts, RR: 26
Reply 9, posted (1 year 7 months 3 weeks 1 day 11 hours ago) and read 5188 times:

Quoting Thumper45 (Reply 8):

Shoot as low ISO as you can go, even if that means you shoot for an underexposed image and have to bump the exposure up in PS (shoot in RAW format if you underexpose, it gives you far more margin to adjust the exposure without loosing quality).

Underexposure will result in more noise when you brighten it in post-processing, though.



How can I be an admiral without my cap??!
User currently offlineRCoulter From United States of America, joined Apr 2007, 555 posts, RR: 0
Reply 10, posted (1 year 7 months 3 weeks 1 day 10 hours ago) and read 5187 times:

Quoting vikkyvik (Reply 9):
Underexposure will result in more noise when you brighten it in post-processing, though.

Exactly, and some Canons like the 7D you actually to shoot as far to the right of the histogram as you can without overexposing as that can help reduce grain.


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