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DPChallenge Forums >> Tips, Tricks, and Q&A >> Canon 20d, view noise in photo on camera
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Showing posts 1 - 11 of 11, (reverse)
AuthorThread
 04/11/2006 07:11:39 AM · #1
Hi Guys,

Sorry to be a newbie once again.... But I was wondering if there is a way on the 20d when you are looking at the photo on the screen, to see if there is any digital noise in the photo. I know that with my old kodak p&s that I could do but but I just cant quite figure it out on my 20d..

Thanks for your help....

Rich
 04/11/2006 01:45:54 PM · #2
Could you be more specific on what noise you mean? High ISO induced noise? Hot spots? jpeg compression introduced?
The only way I can think of is just zoom way in on the picture. Otherwise you just can't see enough detail.
04/11/2006 02:06:58 PM · #3
The LCD screen on the 20D is useless for checking noise IMO; it's not anywhere near fine enough resolution. I guess it might work if you had REALLY bad noise, but the 20D is very good at minimizing noise so...

R.
 04/11/2006 02:42:50 PM · #4
Hi,

To be more specific, I guess when i took a picture with my kodak, it would come up on the lcd and the picture would flash or blink(what ever you want to call it) if there was a loss of data or a place it couldnt read... I was looking for a similar type of method for knowing that at least the camera recorded all the information correctly. I dont nessacarily like the LCD screen either, I cannot usually tell even if the photo is blurry @ 100% or not. Are there any programs out there you can use to judge the amount of noise in a photo?

Thanks Again,
Rich
 04/11/2006 02:47:27 PM · #5
I think you are referring to the Info button. When you click on that while viewing a photo in the LCD screen it may show areas that "blink" as you say however that's showing where highlights have been clipped not noise.
 04/11/2006 02:48:14 PM · #6
That's usually the blown out areas that are flashing. You can do that on the 20d by setting your review screen to the one that shows the small thumbnail and the histogram both. I don't have my camera with me so I forget which button it is but I think it's the info button - try pressing that while you're reviewing your photos until you get the thumbnail and histogram screen.
 04/11/2006 03:15:33 PM · #7
Thanks again for answering my questions, so if the area flashing is blown out, would we need to either adjust our shutter speed/add a polirizer/ or add a nd filter and retake the shot or is there a way to fix blow outs.

Thanks again for all the help, I am trying to understand my camera more to make better images..

Rich
 04/11/2006 03:38:25 PM · #8
Originally posted by thndrdrag:
Thanks again for answering my questions, so if the area flashing is blown out, would we need to either adjust our shutter speed/add a polirizer/ or add a nd filter and retake the shot or is there a way to fix blow outs.

Thanks again for all the help, I am trying to understand my camera more to make better images..

Rich


You basically can't fix 'em, though if it's only a stop or so blown you may be able to recover it in RAW. It's an exposure issue, so reducing the exposure by stopping down or using a faster shutter speed is the answer, in manual mode. In an auto mode, use EV minus compensation.

A ND filter won't help, it reduces light evenly across the whole image, and the camera will still make the same metering decisions. A graduated ND filter will help in certain cases, depending on the distribution of the blowouts within the frame of the image.

R.
 04/11/2006 03:59:38 PM · #9
Bear,

Sorry to keep going on the same subject, but how would RAW be different from JPG when taking a photo? I thought the only difference was compressed vs uncompressed and more data? In stopping down your apreture you mean from say f22 to f11? thanks for your help

Rich
 04/11/2006 04:05:56 PM · #10
RAW data is 16bit, and gives you a little more leeway in adjusting your shot after the capture. You can often push the exposure a stop or so in either direction to recover data that would be lost in a JPEG.

Stopping down the aperture means using a smaller "opening" to expose the camera's sensor, which is actually a larger number (going from f/3.5 to f/5.6).

Message edited by author 2006-04-11 16:06:57.
 04/11/2006 04:29:26 PM · #11
Sometimes you have to live with part of the picture blown out so that you get the important parts correct (e.g. you may intentionally overexpose the window when you take a group shot in a dim room).

If this bothers you, your camera has the ability to automatically bracket the exposure. This means that you can take shots at different exposures then composite them in post-processing.

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