Polariser plus SLT - blotchy sky problem

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Greg Beetham
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Re: Polariser plus SLT - blotchy sky problem

Unread postby Greg Beetham » Tue Sep 18, 2012 2:28 am

Ed I was just thinking about the blotchy stuff in the sky appearing lately in images and wondering if it varies if a RAW file is processed twice and the jpegs compared with each other, if the same blotches appear in the same place then it’s most likely the camera (maybe) but if there is a different set of artefacts then the problem is most likely with the software doing the processing, would you agree with that? That’s why I wondered if the RX100 file might have been a processed RAW (I think the camera does RAW, I didn’t actually check).
Greg

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Re: Polariser plus SLT - blotchy sky problem

Unread postby edrice » Thu Sep 20, 2012 2:30 am

Greg Beetham wrote:Ed I was just thinking about the blotchy stuff in the sky appearing lately in images and wondering if it varies if a RAW file is processed twice and the jpegs compared with each other, if the same blotches appear in the same place then it’s most likely the camera (maybe) but if there is a different set of artefacts then the problem is most likely with the software doing the processing, would you agree with that? That’s why I wondered if the RX100 file might have been a processed RAW (I think the camera does RAW, I didn’t actually check).
Greg

Greg, Adobe hasn't come out with a released camera raw yet for the RX100 and the IDC is too painful for me to goof with, so while I still take raw shots I haven't really done anything with them except for a couple so far.

But you have an interesting question. I don't remember what file-type I used in the previous examples, but I should look for NEX or A65 samples where I still have both and compare them. I don't remember if I did this in the past. I may have to retake some test shots.

Ed

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Re: Polariser plus SLT - blotchy sky problem

Unread postby Greg Beetham » Thu Sep 20, 2012 6:06 am

edrice wrote:Greg, Adobe hasn't come out with a released camera raw yet for the RX100 and the IDC is too painful for me to goof with, so while I still take raw shots I haven't really done anything with them except for a couple so far.

But you have an interesting question. I don't remember what file-type I used in the previous examples, but I should look for NEX or A65 samples where I still have both and compare them. I don't remember if I did this in the past. I may have to retake some test shots.

Ed


Yeah duh! I was forgetting the camera is too new for Adobe yet, and I have heard that processing in IDC is pretty much equivalent to what you get with a camera processed JPEG anyway, I don’t know how true that is as I’ve only ever dabbled a little bit with the program and I’m no expert at processing RAW but I have done a couple here and there where I wanted to fix something, shadows or highlights mainly, I’d really want the photo to bother with that though.
What is interesting though is somehow you always get a thumbnail of the RAW in any Adobe program no matter if it’s an unknown camera or not, where is it getting that from? The thumbnail must be an image file of some kind in actuality even though the filename has a .RAW file extension, RAW is only a bunch of data…or so I’m led to believe, some say it’s from an embedded JPEG, well if that’s the case why bother shooting RAW + ExFine JPEG for each shot. Maybe the embedded JPEG is a very small file just for the rear screen on the camera or something such and only roughly assembled. But what if Adobe takes a que from how that was done?
I guess Ed if you are going to do a few test shots why not put the camera on a tripod and take exactly the same shot twice in quick succession and see what happens to the blotches then, whether they are the same each time or different, again I’d be inclined to suspect the software if they are noticeably different.
Greg

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Re: Polariser plus SLT - blotchy sky problem

Unread postby artington » Thu Sep 20, 2012 9:53 am

I am using LR 4.2 RC which does process Raw files from the RX-100. I know its not the final telease but I've had no problems with it.

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Re: Polariser plus SLT - blotchy sky problem

Unread postby edrice » Mon Sep 24, 2012 12:49 am

Greg Beetham wrote:Yeah duh! I was forgetting the camera is too new for Adobe yet, and I have heard that processing in IDC is pretty much equivalent to what you get with a camera processed JPEG anyway, I don’t know how true that is as I’ve only ever dabbled a little bit with the program and I’m no expert at processing RAW but I have done a couple here and there where I wanted to fix something, shadows or highlights mainly, I’d really want the photo to bother with that though.
What is interesting though is somehow you always get a thumbnail of the RAW in any Adobe program no matter if it’s an unknown camera or not, where is it getting that from? The thumbnail must be an image file of some kind in actuality even though the filename has a .RAW file extension, RAW is only a bunch of data…or so I’m led to believe, some say it’s from an embedded JPEG, well if that’s the case why bother shooting RAW + ExFine JPEG for each shot. Maybe the embedded JPEG is a very small file just for the rear screen on the camera or something such and only roughly assembled. But what if Adobe takes a que from how that was done?
I guess Ed if you are going to do a few test shots why not put the camera on a tripod and take exactly the same shot twice in quick succession and see what happens to the blotches then, whether they are the same each time or different, again I’d be inclined to suspect the software if they are noticeably different.
Greg

We've had some high clouds in the area the past few days and I haven't had an oppotunity to test these scenarios, but I'll get to it when the time is right.

Ed

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Re: Polariser plus SLT - blotchy sky problem

Unread postby edrice » Mon Sep 24, 2012 12:52 am

artington wrote:I am using LR 4.2 RC which does process Raw files from the RX-100. I know its not the final telease but I've had no problems with it.

It's my understanding that they don't have a lens profile for the RX100 yet and I was kinda waiting around and hoping for that.

Ed

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Re: Polariser plus SLT - blotchy sky problem

Unread postby Dr. Harout » Mon Sep 24, 2012 8:14 am

Update: I've noticed some blotchy skies without any polarizer but under specific conditions and in Georgia (lower altitude, autumn sun, blue skies...). Unfortunately didn't use any polarizer there.
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Re: Polariser plus SLT - blotchy sky problem

Unread postby David Kilpatrick » Tue Sep 25, 2012 1:42 am

Further update: all AA filters have a polarizing effect. That's why digital pictures can sometimes look as if a polarizer has been used. It's complex but after doing a bit of reading, I think it is more likely the AA filter assembly causes patchy effects than the SLT mirror.

David

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Re: Polariser plus SLT - blotchy sky problem

Unread postby edrice » Sat Sep 29, 2012 11:47 pm

edrice wrote:It's my understanding that they don't have a lens profile for the RX100 yet and I was kinda waiting around and hoping for that.

Well, I just got around to installing the ACR beta release and distortion-wise, I can't tell any difference between the jpg and the raw, which must mean that they have a profile in there. But when I checked the drop-down box, ACR doesn't list one for the RX100. Nevertheless, when I click back and forth between jpg and raw, there is no movement.

And I have to say that I am pickled tink with the RX100 raws. Definite improvement over the jpgs, which were already good.

So, now I'll continue forth checking out the polarizer anomaly.

Ed

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Re: Polariser plus SLT - blotchy sky problem

Unread postby David Kilpatrick » Mon Oct 01, 2012 1:04 am

Just checked ACR raw va JPEG on RX100 - yes, there is a tiny difference but you have to use a large screen preview even to spot the shift.

David

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Re: Polariser plus SLT - blotchy sky problem

Unread postby Juanito200 » Tue Oct 02, 2012 10:33 pm

So now that I have an a77, I have read through the posts here, as I use polarizers often. This was from the first sunnd day in a while here, and this is what I got. I haven't seen it again, but I still have some shots from today to go through. This was taken with a77 and 70-200 G. No polarizer. The banding was visible in the viewfinder and the screen. I thought it was just from the screen, but it was in the RAW files as well.
ISO 200, f2.8 1/8000 sec. Obviously, not optimal settings, but what caused this? The second shot is with a CPL, and pointed at a different pole. It is underexposed, but when you correct it, no bands appear.
Is the first one just a weird confluence of sun angle, SLT mirror, f2.8, and operator error?
Thanks, John
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Re: Polariser plus SLT - blotchy sky problem

Unread postby edrice » Thu Oct 04, 2012 12:10 am

David Kilpatrick wrote:Just checked ACR raw va JPEG on RX100 - yes, there is a tiny difference but you have to use a large screen preview even to spot the shift.

Yes, I do see that tiny shift difference, but it looks like most of the image is shifting itself upwards (I checked all corners) and I thought at first it was just changes in lighting patterns between jpgs and raws. But I think I see the same thing in IDC although it's harder to tell because I get a "jump" or "bounce" switching between jpg and raw. ACR has a much smoother transition so it's easier to see the shift. But what this tells me is that ACR must have a slghtly different lens profile than the in-camera jpg conversion. Am I wrong? This tiny shift is nothing on the order of the mega barrel distortion that we see in the raws that is corrected in the jpgs and I checked it from wide angle to tele and there is just not that much shift in any of them.

Ed

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Re: Polariser plus SLT - blotchy sky problem

Unread postby agorabasta » Thu Oct 04, 2012 8:18 am

Adobe now has two nice plugins for Lr/ACR. First is meant to recover full raw data from the metadata-cropped raw, the second one is to correct purple shift in the corners. Download here - http://labs.adobe.com/downloads/lightroomplugins.html

I didn't try uncropping the RX100 files, but it may work...

(a later) P.S. Just checked, and uncropping with that plugin doesn't do much to RX100 files; it just expands them by a few pixels.

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Re: Polariser plus SLT - blotchy sky problem

Unread postby Greg Beetham » Fri Oct 05, 2012 3:31 pm

John that sky reproduction is not good, in the second one the low level haze has not been dealt with very well, it has a ragged appearance, there is also a peculiar blotch a bit left of the middle of the frame and upper level horizontal low contrast bands, I don’t know what to make of the first one.
I still think it’s the sheer amount of reduction…mostly, to get the 24Mb file down to 180Kb represents about a 99.3% reduction in file size, that means the program has to figure out a way of reducing it by that much (throw away 99% of the file) and still make the result look something like the original.
Like I’ve said before I can get artefacts in the sky with both the A100 and A700 as well (I habitually use mainly the camera JPEG’s, let’s face it the end result is to produce a JPEG anyway whichever way you do it) if I reduce the files too much, (smooth transitions start to get ragged) and that’s with all ‘in camera’ embellishments turned off or set to zero, there is more potential for problems I think if any of those are used.
If I stay close to 250Kb or at least above 200Kb it’s not so bad, the ragged edges diminish down to a level that you hardly notice, and those cameras have files half the size the A77 produces, I’m wondering what a sky JPEG from the A77 would look like at around a half megabyte quality level, I bet it would be a lot better than a 180Kb one.
Another problem is it seems Adobe can’t work on large JPEG’s that are bigger than 8bit so if you are converting from 16bit RAW to JPEG you get a message that the file has to be converted to 8bit, and that conversion could be a potential source of problems if the conversion is attempted before the size of the file is reduced…I think. This Adobe tutorial is interesting http://www.photoshopessentials.com/essentials/16-bit
Greg

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Re: Polariser plus SLT - blotchy sky problem

Unread postby Greg Beetham » Sat Oct 06, 2012 11:27 am

I took a few shots with included sky today as the sky was reasonably clear just to see if I could get any artefacts to show up both with a camera jpeg and a converted .arw-psd-jpg process by comparison. I have to admit that I didn’t notice too much wrong with the camera .jpg file on this occasion…even though I deliberately went under the 200Kb threshold that I like to stay above, (there does appear to be some slight banding though when looking at the preview after uploading, not noticeable before, probably to do with the angle its looked at on the screen...maybe).
I took the same photo with all three of my cameras but I haven’t downloaded from the other two as yet, but I will if anyone is interested.
Greg
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