Artifacts


thingsthatihaveseen

Link Posted 27/05/2014 - 13:00
Hi all

I wondered if you might be able to help me with something I've noticed a couple of times recently... when shooting tall thin structures (lighthouses, chimneys etc), I sometimes get artifacts/halos around the form of the structure itself...

This occcurs BEFORE I apply any form of clarity/sharpening to the photograph, although I've noticed that it tends to increase the more contrast/clarity/sharpening I apply...

The shot below (taken at Whitby) shows artifacts along the line of the lighthouse on both sides... btw, I'm not referring to the obvious chromatic aberrations (which I can get rid of quite easily) around the exact outline of the structure, but rather the apparent "shadows" slightly further out on either side...

This was shot in RAW, with a K5 and Sigma 10-20 f4-5.6, a 3 stop nd and 0.6 nd grad, iso 80, f16, 1.3 secs... This is as shot, no sharpening, clarity, contrast applied, just brought the highlights down a tad and desaturated slightly...

Anyone help me with what's going on here, how to minimise its effect on this photograph, and how to avoid it in future?




Thanks very much in advance

Best
Bill

BillWardPhotography
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Last Edited by thingsthatihaveseen on 27/05/2014 - 13:05

fritzthedog

Link Posted 27/05/2014 - 16:27
Hi Bill

That is really strange.

I go to Whitby virtually every month. I have photographed that lighthouse more times than I care to think.

My normal set up for this sort of shot is:

K5 + Sigma 10-20

Generally the 10-20 has a CPL on it plus if needed - ND grad 0.3,0.6, 0.9 or a combination of these.

So the only difference is I am using a CPL + ND grad(s) and you are using a solid ND + grad. I have never experienced a 'ghosting' artifact like that.

So the first question would have to be - is it a filter problem? What happens if you do not use a filter? What happens if you just use the solid ND or just the grad? Is it a stacking problem?

Carl
No matter how many lenses I have owned - I have always needed just one more

thingsthatihaveseen

Link Posted 27/05/2014 - 16:58
Hi Carl

Thanks very much for your reply... yes, could be the stacking... hadn't thought of that actually... although, below is another example of it, this time with the K5 and Pentax 10-17 Fisheye, 15 sec exposure, iso 80, f20, some clarity and contrast applied, but no sharpening... and being the fisheye, no filters...

Any more thoughts?




Best
Bill

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fritzthedog

Link Posted 27/05/2014 - 17:23
Hi Bill

OK - so crossing off a filter problem from the list...... next thing I would check would be the software you are using to import the image to your PC. Could it be a RAW processing issue? - not talking about processing the image - just the import conversion.

Does it happen if you shoot in jpeg? Try shooting RAW+ and see if you get one with and one without the artifact

What software do you use? Do you have something else you could try?

Carl
No matter how many lenses I have owned - I have always needed just one more

thingsthatihaveseen

Link Posted 27/05/2014 - 19:35
Hi Carl

Thanks again for your post... interesting... software-wise I only use Lightroom 5, for importing images, developing them, then exporting them again.

Technology absolutely not my thing, but as far as I know I shoot in raw (DNG) and also edit as a raw file, also DNG. So no conversion as such as far as I know. I don't convert until I export (usually as a jpeg), and the ghosting/artifacts are definitely present on the raw file itself before conversion for export as a jpeg.

Haven't tried Raw+ yet of the original image (usually only shoot RAW), but that's worth looking at next time I'm out shooting this kind of thing.

If anything else should occur to you, do give me a shout...

Thanks again

Best
Bill

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fritzthedog

Link Posted 28/05/2014 - 18:18
I use LR4 and do not get any issues so can not think LR5 would be a problem. Still try a few on Raw+ and check jpeg Vs Raw. if it isn't filters, lenses or software - by a process of elimination - that would only leave the camera!

Carl
No matter how many lenses I have owned - I have always needed just one more

MattMatic

Link Posted 28/05/2014 - 20:09
From an initial look I reckon there are a couple of things going on.
First, there is a fair amount of uncorrected CA that is causing a bright edge. It is green/purple and LR has done most of it, but not all.
Secondly, it looks like rain pouring down from the top of the tower producing a feint darker band either side.

It is also possible that the stacks of filters have added to the issue, but it looks mostly like CA at 10mm.

Will look in more detail tomorrow...
Matt
http://www.mattmatic.co.uk
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thingsthatihaveseen

Link Posted 28/05/2014 - 22:59
Hi Matt

Thanks very much for this... yes, could be a bit of CA... am not very good at correcting that over and above the default lens correction tools on LR... would any other software do a better job of that d'you think, or do I just need to get a bit more skilled with LR?

Definitely not rain though down the sides of the tower - dry when I took the shot of the Mill, and no water coming down the side from anywhere else I don't think...

Thanks again for having a look, and do let me know if you find anything else...

Best
Bill

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thingsthatihaveseen

Link Posted 30/05/2014 - 17:33
Massive thanks to Matt for having a forensically hard look at the original DNGs of these... really good of you and much appreciated...

So, how can I put this nicely? Oh... I can't... turns out I'm a bit of an idiot (my words, Matt was much more polite than that!).

So... actually these files DID already have a fair bit of editing on them, which is almost certainly responsible for the artifacts... So although I thought they were pretty much as shot, no clarity, contrast etc applied, turns out quite the opposite... a fair bit of clarity, grad filter, brush etc applied... ooopps...

I tend to move around a lot with work, and take files with me to edit on the hoof... so even though I reset the dng of this shot before I uploaded it, turns out it was only THIS version I reset, which still had a fair bit of editing on vs the original (which was taken 6 months or so ago)... so apologies for that...

Quite possible the marks either side of the lighthouse are either brush with no automasking, or brush with feather still attached.... or a build up of clarity adjustments from brush, grad filter, and universal clarity adjustments... or quite possibly, I suspect, a combination of all three...

So... Thank you Matt and Carl for all your help on this... am going to head back to the original DNG and start from scratch... in the meantime, will see if I can find a handy sword to fall on...

Best
Bill

BillWardPhotography
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