Author Topic: A850 posterisation in shadows  (Read 3301 times)

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Offline simond

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A850 posterisation in shadows
« on: February 16, 2012, 10:44:44 PM »
Hi

This is my first post here so firstly hello to the forum members.

Sorry for the first post being a whinge, but here goes.

I have a Sony A850 and wanted to ask about posterization in shadows and lower mids. I have a Nikon D200 and that renders all tones perfectly smoothly with comparable noise levels, though not the resolution of course. The posterization is not just in deep shadows its in many areas where there is only slight variation in tone - the subtle shading is lost to blocks of solid colour with pixelated boundaries. I also see bands of colour shifting in other tonal areas again when there is a slight transition. I know these are not simply limitation of the scene on the technology because my humble D200 can capture the same scenes with no issues and the A850 is much more advanced.

Anyway, just wondering if this is normal for the A850 or not?

Thanks.

Offline tpe

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Re: A850 posterisation in shadows
« Reply #1 on: February 16, 2012, 11:00:20 PM »
I think I know the type of posterisation you mean. However I dont see the same with my a900, but perhaps this is because i shoot in craw as the image size seems to be the same as xfine jpg? The jpg engine is not great and often enough this type of banding can turn up in jpgs but not in the original raw. Also this can be made more visable on older lcd moniters, as these sometime have difficulty similar with dark shades. I do see a fair bit of noise even at iso 200, and i guess this could also be a bit like posterisation, but not sure that is what you mean either?

Tim

Offline simond

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Re: A850 posterisation in shadows
« Reply #2 on: February 16, 2012, 11:17:02 PM »
Thanks Tim. I do see it on the camera LCD, but this may be because that display is probably some kind of Jpeg - I don't know. I only shoot RAW (cRAW) and import to Lightroom/Aperture. I first noticed it in Lightroom on some cloudscapes I shot.

I always shoot at he lowest ISO I can, and the A850 is excellent at that thanks to the stabilisation. Brilliant in fact. But this quantisation is killing image quality despite my best efforts. Increasing ISO decreases the posterization somewhat - this is to be expected as those who work in Photoshop will tell you a good dose of noise can really help with banding in gradients. The ISO noise has a similar dithering effect, but I think the posterisation is basically still there.

I love everything else about the camera excellent for the money and it's really annoying that its falling down on just this one thing. I'm wondering if there is some setting somewhere that I've dialed in wrong, but shooting RAW I don't see how.


Offline AScot

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Re: A850 posterisation in shadows
« Reply #3 on: February 16, 2012, 11:49:48 PM »
Definitely not normal on the A850/A900. Check that APS-C size capt. (Item 4 in the spanner menu) is not ON. I doubt that that would produce posterization but I can't think what else would at the moment, other than possibly using ISO 100 as you do. You should know that the minimum recommended ISO on the A850 is 200, not the usual 100 and although there are many different opinions as to what is the best minimum to use (ranging from 160 to 320) I always use 200 ISO.

As I am sure you know, posterization or banding would normally be produced by reducing your number of colours in post processing. That is where I would normally look first for the problem, not in the camera. However you say you are shooting RAW and the banding shows on the LCD display. The display is from a .jpg but is of very high quality, although the engine may be suspect by some. So I am stumped on this one as I have never experienced banding from the A850.
Sony A7, A850, A77, A700 || Sony>> 70-300G, 28-75 f2.8 SAM, 16-80CZ, 50 f1.4, FE 28-70 OSS, FE 24-70CZ f4 OSS, LA-EA4 || Minolta>> 300 f4 G HS, 200 f2.8 G HS, 100 f2.8 (D) Macro, 50 f1.7, 28 f2.8, 28-135 f4-4.5, 70-210 f4, 500 f8 Reflex, TC x 1.4 HS, TC x 2 HS. || Sigma 21-35 f3.5-4.2. || Tamron SP 24-135.

Offline simond

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Re: A850 posterisation in shadows
« Reply #4 on: February 17, 2012, 12:27:11 AM »
Holy moley! Its Aperture not the A850.

If I import the RAWs into Aperture and view the enlarged image on a 2nd monitor the image is covered in JPEG artefacts and posterization. I was looking at it at 1:1 then 2:1 and just couldn't figure it out. It was like Aperture wasn't actually importing RAWs. So I opened an ARW directly in Photoshop Camera RAW, zoomed in and saw a different image - much cleaner.

I thought I was going mad, but if you view an image in Library mode in Aperture and view a fullscreen preview of it on a 2nd monitor the image is NOT the real image, its a poxy Jpeged version. Yet it gives you the spinning waiting wheel as if its loading the real file. But it isn't. Swtich to Develop and the image instnatly improves. Bug?

OK so there is still some posterisation and higher than expected noise at ISO 100 but it's not the disaster I thought I had on my hands.

I didn't know ISO 200 is the recommended min. I will give that a try.

thanks for the replies and help.





Offline chappo1

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Re: A850 posterisation in shadows
« Reply #5 on: February 17, 2012, 05:14:55 AM »
Welcome to dynaxdigital.  ......john
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Offline simond

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Re: A850 posterisation in shadows
« Reply #6 on: February 17, 2012, 11:28:24 AM »
Thank you john. Pleased to be here.


Offline Rob aka [minolta mad]

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Re: A850 posterisation in shadows
« Reply #7 on: February 17, 2012, 11:15:46 PM »
Hi and welcome to the forum.
Its also worth checking that you have the latest firmware installed as well.
I suffered quite a bit of posterisation with the A900 when i first used it, but that was down to Adobe not fully supporting the A900's RAW fles and learning how far you can go with levels and curves adjustments (whicg are the two worst things for making it worse) before it appears.


Rob