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PostPosted: Sun Oct 30, 2011 7:33 pm 
Hi guys,

I recently got a 7D and found that the images I take at ISOs 100 200 and 400 ( lower values) are very noisy. I had a Rebel Xs before this and had no such issues with it at these ISOs . People told me that the 7D takes really sharp images but Im not able to get any. Do you have any idea why this is happening? Is there something Im missing?

I've attached an image to show what I mean :

Image
Tide Pools by Lens_Kaiser, on Flickr

Look at the sky in particular. It's so grainy and noisy. FYI, I combined 3 different exposures to get the foreground as it is. Without them, it was very noisy too.


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PostPosted: Sun Oct 30, 2011 8:31 pm 
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Some EXIF data or information about your settings would really help and to be honest I don't think that picture says a great deal - seeing that it's been further compressed (I did check the "Large" image at Flickr) and resized, I'm not sure if the apparent noise is from the camera or if it's just the compression that's reduced the quality.

Just about any DSLR of the past couple of years, regardless of price, can give you sharp images but sharpness is generally more dependent on the lens you use, not the body. I've used a 7D for a weekend and I was delighted with the results.

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PostPosted: Sun Oct 30, 2011 9:05 pm 
The shot was taken with

a Canon 17-40mm wide angle L lens

ISO 200

Aperture Priority mode

f/11

Three exposures -2 0 2

I have a bunch of bad images on my hard drive but Im not able to upload them here... Is there a way?


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 Post subject: noise
PostPosted: Sun Oct 30, 2011 9:50 pm 
Noise is hard to judge with an hdr a normally shot photo would be better. The under exposure shot will generate extra noise than one normally exposed. I have read that the 7d generates some noise at low ISO and I think gordons review shows this. You can't have all those extra pixels without some compromise. As for sharpness tho this should defo not be an issue you must have a faulty cam or be making a basic error. If you are confident you know what you are doing (no offence) then I would get the cam checked over...


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PostPosted: Sun Oct 30, 2011 10:31 pm 
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agree with comments on hdr not being a good place to look for noise.
Were these processed form raw of jpg?

Suggest you put up a 100% crop of one of the photos you used to create the hdr.

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PostPosted: Sun Oct 30, 2011 10:50 pm 
The images were processed from RAW not Jpeg.


Is there a way to upload images with the post? I have a 100% crop of an image of the sky which clearly shows what I'm talking about.

I'm positive that I focused correctly, every thing was set accurately. I don't understand why it's happening.


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PostPosted: Mon Oct 31, 2011 7:38 am 
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You may have answered the question there. RAW is inherently more noisy than JPEG as much less processing was done to produce the image. You would have to do some PP to reduce the noise.

Your focus has nothing to do with the noise - subjects that are out of focus and noise are not the same thing.

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PostPosted: Mon Oct 31, 2011 3:12 pm 
agreed. But I'm concerned more with the grainy nature of the image. I can understand if this were the case at higher ISOs like 1600 and so.. but something like this at ISO 100 is scary...

Thats what Im trying to understand here.. why that's happening


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PostPosted: Mon Oct 31, 2011 4:13 pm 
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It's probably something going on in your processing. If you exported JPEGs from RAW before doing your HDR then any sharpening you might have done to those pre-HDR JPEGs would exaggerate any noise/grain in the final output. Run the RAWs through some noise reduction, do your HDR thing, and then sharpen the final output... Hope that helps...

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PostPosted: Mon Oct 31, 2011 4:17 pm 
@Plymer: Actually, I didn't do anything except convert them to jpegs before processing them. I wanted to show the image quality as it was..

do you have any ideas why this is happening?


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PostPosted: Mon Oct 31, 2011 5:09 pm 
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Image noise has two sources: temperature and signal/noise ratio. Even at base ISO current sensors produce noise -- especially in underexposed areas that are being lightened in post processing. Also forget about sharpening filters if you are serious about noise. You will always have to do it manually through masks.


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PostPosted: Mon Oct 31, 2011 5:12 pm 
hmmm.

I had a Canon Rebel Xs before this one and the image quality in general appeared better.

If I shot the same scene with the two cameras at the moment, the rebel seems to have a better image quality which is shocking.

Does that mean I got a lemon?


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PostPosted: Mon Oct 31, 2011 5:47 pm 
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Hi sairam6087,

Unfortunately the forum cannot host images or RAW files. To share images you'll have to upload them to your Flickr account. The only way to share RAW files would be to upload them to some other third party site and then link to them via the [url]..[/url] tags.

I agree with other members that HDR images are not too useful in diagnosing potential problems. Far better is a correctly exposed single image from which you can share 100% crops as needed as well as a link to the complete image.

You don't share your workflow. If you are using Canon's DPP to convert the RAW images to JPEGs then it should be picking up the in camera settings for sharpening, saturation etc. unless you are over-riding them. If you are using a third party RAW converter then all bets are off in that regard.

Without the ability to share a RAW image maybe you could follow up my suggestion to share a correctly exposed single image from which you can share 100% crops as needed as well as a link to the complete image. And because Flickr eats EXIF data it might be useful to not only do the RAW to JPEG conversion in Canon's DPP but also to use DPP's Info window (from the file menu) to not only bring up the shooting information but then to use the mouse to select all the text and then copy and paste it into your post with the photos. You can, of course, edit out irrelevant info like the camera body number before you hit the Submit button.

Extra work, I know, but it will probably give fellow members the best chance of diagnosing the issue.

Bob.

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PostPosted: Mon Oct 31, 2011 5:55 pm 
Hi Bob,

Yes. I'll do that as soon as I get back home from work.

As for my workflow,

I always shoot in RAW. Import images into Adobe Photoshop Lightroom 3, convert to jpeg using Lightroom.

(I do all my post processing in Lightroom and CS5) .

I'll follow up on your suggestion and put up pictures on my flikr account.

Thanks for the assistance!


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 Post subject:
PostPosted: Tue Nov 01, 2011 4:51 am 
Here is an image with the exif data that I shot : no post processing what so ever:

Image at 100% crop:

Image
7D noise at ISO 200 by Lens_Kaiser, on Flickr


Exif info:
http://www.flickr.com/photos/50038436@N06/6301482008/meta/in/photostream/


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