Noise and Canon 7D

[TobyMac]

Hello All
I just recently got the Canon 7D and am overall very happy. However I have noticed that all my pictures seem to have a lot of noise in them, even at 100 ISO. Is this normal? I have noticed that when I look through the viewfinder and the image is out of focus the image is very grainy, but when I focus on the subject, this grain goes away, so it seem to be something in Camera, might this be the cause?
I might just be paranoid but when I printed the image below it became very apparent to me and that was only on an A4 print.

Here is a sample image.
http://www.flickr.com/photos/tobiasw...hy/6990329793/

and a closer crop to make seeing what I mean a bit easier.
http://www.flickr.com/photos/tobiasw...in/photostream

[herbert]

Hi Tobias,

1. Viewfinder

The Canon 7D has an LCD overlay on the viewfinder. This allows it to show the auto-focus points, spot metering zone, composition assist grid, etc. This takes power to run and when the camera is on it is barely visible. Turn the camera off and you will see that the viewfinder gets very dark and looks grainy.

It may be that you are noticing the grainy overlay when the camera is on. If the grainy look is similar to that seen when the camera is turned off then this is the overlay. Canon do not make interchangeable focussing screens for the 7D. I think there are some third party screens that you can get but it would void the Canon warranty. So you could change the screen, but then you lose all the nice functionality it provides.

2. Image noise

The 7D does produce noisy files when you view them at 100%. Noise is the worse in the blue channel and is always most visible on smooth tonal transitions. This may be similar in any other camera of the same generation (or earlier) with the same sensor pixel size. It is just because the electronics are not perfect.

However you can do something about it in post-processing. Any sharpening will enhance the visibility of noise. If you are doing capture sharpening to make all your pixels appear crisp then you will also make the noise more apparent.

Using in camera JPEGs does not give you many options with the sharpening. Not the options that are required anyway. Shoot the images in raw and take some care over what is sharpened. This means using an edge mask to only sharpen the edges. The smooth tones can be left alone and the noise will not be so apparent.

Edge masking is easy to do using Photoshop/Lightroom. I am not sure about your software options but someone here will be able to tell you how to do it in your software of choice.

Also note that the noise of the 7D has nice characteristics. The noise shows very little banding which is very hard to remove. The noise is mainly colour noise and luminance noise. Both of these can be removed with noise reduction software. However this can make your images lose sharpness. In this case you will want to invert your edge mask to make a surface mask and only reduce the noise where it is most visible. That will be a job for Photoshop.

Note that image noise is not totally evil. When preparing an image for the web you will down sample the image and the noise will disappear. When printing you can show all your pixels from a 7D at approximately 18x12 inches at 300 ppi. In this case the noise will add a bit of texture to smooth tones and prevent the print from looking 'too digital'. Sometimes when noise reduction has been over done on an image it is nice to add a bit of noise back to make the print better. If you are printing smaller then the down sampling will again get rid of the noise.

Alex

[TobyMac]

Thank you so much Alex Very helpful Info

[TobyMac]

I know this might be a bit complicated to explain, but my mom would like to have some of my photos printed in A3 size, how do I go by making sure that the print quality is as good as possible?
I shoot in RAW and have Photoshop Elements 10 to work with.

[herbert]

Hi Tobias,

This is a quick printing crash course; ask questions to fill in the blanks.

To print that big you will get the best results if you use your entire frame from your image with no resizing. The 7d is 5192 pixels wide. A3 is 16.54 inches. That makes 314 pixels per inch (ppi). This is close to the 300 ppi standard for high quality printing. So make sure you choose images that use the full image size (no cropping) and then make sure you can get them printed by someone who will accept the full size file.

To get a nice print you will need to sharpen the image for the print resolution. The idea is to have a sharpening halo of about 1/100 to 1/50 of an inch. This is a size that the eye cannot detect from a standard viewing distance. That will be 3-6 pixels on your 300 ppi image. In reality this means you can sharpen the image so you see halos of 1-2 pixels wide on either side of an edge.

To ensure you get good colours it would be best to print a few different images at a small size. You can then work on your colours if there are issues. It is important that you are working with a colour managed system. This means that the system reproduces colour in a standard way, i.e. to match a known set of colours. So when you send the image to another location it will be represented as best it can by the new system which is set up using standard colours.

If your monitor is showing bad colours then when you edit it you will compensate for that. The image you send to print will then have skewed colour.

Once you have editied your image for colour and content, chosen your output size and resolution, resized (not needed for the 7d at A3 sizes) and performed appropriate sharpening you are ready to print. Either you have your own printer or you need to find someone who will do a3 prints for you without manipulating the file you provide. Ideally this will be someone you can use for small test prints on the same printer too.

Hope that helps.

Alex

[TobyMac]

Cool Thanks a lot. I never really printed my images bigger than A5 so this is all very new to me. Where can I see in Photoshop at what resolution I am, I know that if I go into the Image section and then to re size there is a box that says resolution, is this my actual resolution? If so, why is it only at 240?

[herbert]

Hi Tobias,

The resolution in photoshop is a label. It states have much you want to spread out your pixels when you print. It does effect the actual image pixels.

You can change the resolution in the image size dialog. Just type a new resolution and leave the dimensions to auto rescale. These will show your dimensions for the printed image at your new ppi.

The 240ppi is probably a default set when you open your image or create a new one. This can be changed within the preferences settings.

Alex