Dust map in Lightroom?

[iblink]

Hi

Anyone know of a Lightroom plug-in or workflow that would allow me to quickly make and apply a dust map? It would likely work the following way:
- shoot an image with white plexi against the lens. This is the dust map reference.
- Analyze the image to create a "map" of dust and, likely, any uneven illumination.
- Apply this map to new captures, as they come in.

I have a custom back that has a few spots that I would like to automatically or quickly remove. I am aware of Adobe's flat field plug-in, but it does not remove dust, and, in any case, it's a bit of a nuisance to use.
One could eventually script this in Photoshop, but I have been unable to find a plug-in or workflow for PS.

Any ideas?

Thanks,

- M

[Schewe]

Pretty easy...take the dust image that you've already spotted then the real image that needs spotting and do a Sync with the dust image most selected and the other image also selected. Pretty sure can't do this at import but once the images are imported select all and sync...

[adias]

Pretty easy...take the dust image that you've already spotted then the real image that needs spotting and do a Sync with the dust image most selected and the other image also selected. Pretty sure can't do this at import but once the images are imported select all and sync...

Right! That is what the OP seems to want, but does he really want to do that blindly?  A dust map applied to a generic image will remove the dust correctly on smooth surfaces (e.g., sky) but on parts of the image with detail all bets are off re the final result in those areas.

[Schewe]

Yep...after syncing you need to double check that the spots are in the right spot. But that vastly easier that starting from scratch. I've shot a lot in Antarctica which is very, very dusty...I learned this early on (it just wasn't worth trying to clean the sensor cause it seemed to add more crap on the lens). But checking the spots after syncing is still easier than starting from scratch each time...

[adias]

Yep...after syncing you need to double check that the spots are in the right spot. But that vastly easier that starting from scratch. I've shot a lot in Antarctica which is very, very dusty...I learned this early on (it just wasn't worth trying to clean the sensor cause it seemed to add more crap on the lens). But checking the spots after syncing is still easier than starting from scratch each time...

Maybe Eric could engineer a paintable mask to delimit large areas where healing/clone spots could be deleted in one fell swoop.

[Schewe]

Maybe but your user case would need to be stronger that this since there's a way to do what you want...(even if it takes several steps).

Sorry, be careful what you ask for and only ask for what you really, REALLY need (that's my experience).

[Bart_van_der_Wolf]

Maybe Eric could engineer a paintable mask to delimit large areas where healing/clone spots could be deleted in one fell swoop.

Hi,

What would be really useful, and it frankly amazes me that it's still not an integral part of LR, is a function to remove dust by removing it from the Raw data itself, as a variation on the Adobe DNG Flat Field plug-in.

This functionality is available in e.g. Capture One, and RawTherapee, and it works really well. All that's required is an additional Flat field shot, taken with the same aperture as the shot that needs to be repaired, and the dust/smudges/what have you is gone (also from areas one may have missed on an actual shot due to being obscured by detail). I use that a lot with narrow aperture close-up shots, or landscape and architecture shots, and e.g. with focus-stacking where dust spots form a trail of spots due to the magnification differences between stacked slices.

Cheers,
Bart

[iblink]

Thanks for all the comments -

BartevanderWolf has it right -- that is exactly the type of functionality that I'm looking for, although like the FF plug-in I would want it to work with tif files as well. I am aware that one can sync manually spotted images, I just do not want to have to manually spot a reference image every time I change f/stop, focus or lens (I use a technical camera, so the spot location is highly sensitive to these variables.)

[adias]

Hi,

What would be really useful, and it frankly amazes me that it's still not an integral part of LR, is a function to remove dust by removing it from the Raw data itself, as a variation on the Adobe DNG Flat Field plug-in.

This functionality is available in e.g. Capture One, and RawTherapee, and it works really well. All that's required is an additional Flat field shot, taken with the same aperture as the shot that needs to be repaired, and the dust/smudges/what have you is gone (also from areas one may have missed on an actual shot due to being obscured by detail). I use that a lot with narrow aperture close-up shots, or landscape and architecture shots, and e.g. with focus-stacking where dust spots form a trail of spots due to the magnification differences between stacked slices.

Cheers,
Bart

I have C1 but never tried that feature. Does it always perform well on textured areas? I have a hard time seeing that it works flawlessly everywhere.

[Bart_van_der_Wolf]

I have C1 but never tried that feature. Does it always perform well on textured areas? I have a hard time seeing that it works flawlessly everywhere.

Yes, it performs well on textured areas. It does not try to fix structures by replacing them with other structures like Lightroom does as a kind of post-processing step. Instead it operates on the linear gamma data, and potentially even before demosaicing (although that depends on how it's implemented). It locally changes the luminosity of the pixels, in proportion to the density of the dust image (LCC). It's an exposure correction that neutralizes the attenuation of the dust, regardless of the detail.

Cheers,
Bart

[iblink]

I can confirm that -- dust removal works great - it's very clean.

-M

[AFairley]

Hi,

What would be really useful, and it frankly amazes me that it's still not an integral part of LR, is a function to remove dust by removing it from the Raw data itself, as a variation on the Adobe DNG Flat Field plug-in.

This functionality is available in e.g. Capture One, and RawTherapee, and it works really well. All that's required is an additional Flat field shot, taken with the same aperture as the shot that needs to be repaired, and the dust/smudges/what have you is gone (also from areas one may have missed on an actual shot due to being obscured by detail). I use that a lot with narrow aperture close-up shots, or landscape and architecture shots, and e.g. with focus-stacking where dust spots form a trail of spots due to the magnification differences between stacked slices.

Cheers,
Bart

+1, particularly since (it appears) the identification of the spots and the adjustment required for removal can be done completely automatically via algorithm.

[Bart_van_der_Wolf]

+1, particularly since (it appears) the identification of the spots and the adjustment required for removal can be done completely automatically via algorithm.

Hi Alan,

That's correct, it's totally automatic. The dust map shot, that was shot through a diffuser, is an almost uniformely lit featureless image. The dust spots stand out as slightly darker, or if there are oil spots there will also be a somewhat lighter/darker ring.

That image, in linear gamma as it comes from the sensor, is normalized to a maximum of 1.0 (decimal number) for the brightest pixels. So now we have a data file with ones for the brightest pixels, and a range of slightly lower/darker values for the dust attenuated spots. The software now divides the actual image data by the dustmap data. That will leave the brightest image pixels unaffected, they get divided by 1.0. The slightly darker dust spot image pixels will be divided by slightly lower dustmap values than 1.0 (e.g. 0.98), and thus get amplified (1/0.98 = 1.0204).

Since that all takes place in linear gamma, colors and detail are not affected, other than that they get slightly amplified/brighter where they were attenuated by dust density.

An actual implementation has a bit more details to deal with, like noise of the dustmap shot, and vignetting/light fall-off across the image, and colorbalance, etc, but the principle is as explained.

So any image detail will get proportionally brighter where the dust made it darker, without altering the actual detail or resolution itself. And as long as the dust didn't move between the actual image exposure and the dustmap shot, the local amplification is pixel perfectly aligned at each sensor position.

Cheers,
Bart

[iblink]

Bartvander -

Yes, your analysis seems quite good. I believe C1 looks at brighter than average pixels as well, and makes the reverse adjustment.

Best,

- M