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Author Topic: Noise  (Read 4364 times)

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« on: February 16, 2007, 03:32 »
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I used a Canon 350D for a couple of years then changed to a Nikon D200 last July.  Snapped away quite happily and thought nothing more until my snaps got rejected by the microstocks (SS and IS).  Not quite sure why they wer rejected, by the rejection made me concentrate hard on getting the best results possible from my D200.

Many people elsewhere complain about noise from the D200.  Many people on these threads have commented on noise, using Neat Image etc in an effort to get through the inspectors.

One of the things I have discovered with my D200 is that correct exposure eliminates all the noise.  And I mean exactly correct, not approximate.

I spent many days experimenting.  And I started doing something I had never done before - using the histogram.  I discovered that 'correct' exposure could be obtained only when the white highlights were edging on the histogram upper limit (edging, not touching).  Automatic exposure never achieved that.  As a result, all of the fifty odd pictures I have taken in the last week have been manual exposure only.

Using manual exposure with the histogram as a guide prodices simply excellent results on my D200, using RAW.

Here is a picture of a prawn I took last weekend using exactly this technique.  All I have done is convert to 100% quality jpeg in ACR.  No other changes have been made in ACR.  Then, I have applied a very small amount of additional contrast and saturation simply to compensate for the softness of the filter in the camera.  Lastly, a miniscule amount of USM (and I mean miniscule).

No other processing.  No noise reduction needed.  There is simply no noise.

Here's the file:

http://www.pbase.com/hatman/image/74432460/original

Anyway, it works for me and my D200.  Perhaps others can try this approach with their cameras.


« Reply #1 on: February 16, 2007, 03:54 »
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Although I agree with your approach and that 'shooting to the right' is a valuable technique. Link to tutorial on luminous landscape I think that if you were to shoot a deep blue sky you would still get noise.  Digital cameras have problems with blues.

« Reply #2 on: February 16, 2007, 04:37 »
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Well I should have known that you would already have been up to speed on this technique leaf, but at least I can have the satisfaction of knowing that I discovered it for myself.

Yes, I've noticed that blues are a problem, and noise can quickly become apparent when upping the blue level.  Presumably the answer is to have a histogram in camera that can show the blue channel?

« Reply #3 on: February 16, 2007, 11:47 »
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hmm.. i suppose that might help a bit yeah, but if you shoot to the right you should be getting the image in the best area despite if you have a specific blue area on your histogram.  You can't just shoot the blue to the right and cut off the reds.

And despite the fact that I have heard about shooting to the right before, I am sure there are others who will find this useful.  I was happy to come across it (on another forum) when I first heard about it.

eendicott

« Reply #4 on: February 16, 2007, 13:31 »
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I don't use Nikon but I'll add to conversation that you have the right technique down (and you can probably adjust that contrast and saturation in the camera) but it also depends on the sensor.

The noise will increase on my Canon 20d when the environment around the camera gets warm.  In the heat of the summer, when the camera has been sitting out (like on a car seat or on a tripod) there will be more noise recorded.

This is also true if you are shooting multiple images.  The sensor tends to heat up and it adds noise.

I haven't noticed it as much on my 30d but then I haven't gone through a hot summer with the 30d yet.

My understanding is that it isn't as much of an issue on full frame sensors.

« Reply #5 on: February 16, 2007, 14:11 »
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You don't necessarily have to shoot in manual mode to get an optimal exposure. I shoot in aperture mode and use exposure compensation to expose images "to the right". This is very easy to do on my camera, which has a big black dial on the back. Even though my camera's exposure is superfreakygood, I still need to tweak it in order to get the lowest possible noise.

I use Noise Ninja on every shot, even when I shoot at ISO 50. My technique is to copy the image onto a new layer, run Noise Ninja on automatic, then adjust the opacity of the noise-reduced layer so that sharpness is minimally effected when viewing at 100%.

Here's a technique I use eliminate those ever-present dust spots. I make two passes at the image, first going up and down in columns, then inverting the image (i.e. making it a negative) and going back and forth in rows - this works particularly well on blue and gray areas such as skies.

Shooting with an ultra-hi-rez camera helps quite a lot, too. I typically downsize my shots to 4MP to further improve things.

These four techniques work very well together - I've had images shot at ISO 3200 accepted on every site! Here are a few:

http://www.istockphoto.com/file_closeup.php?id=2706288
http://www.dreamstime.com/modify.php?imageid=1788044
http://www.shutterstock.com/pic-2515115-a-dark-and-mysterious-forest-is-shown.html

~Stephen
« Last Edit: February 16, 2007, 14:15 by sharply_done »

« Reply #6 on: February 16, 2007, 14:27 »
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Here's a technique I use eliminate those ever-present dust spots. I make two passes at the image, first going up and down in columns, then inverting the image (i.e. making it a negative) and going back and forth in rows - this works particularly well on blue and gray areas such as skies.

Can you explain this part a little more?  I don't understand what you are doing in each "pass".  Are you using some tool from the toolbar?

« Reply #7 on: February 16, 2007, 15:00 »
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I use the close tool on each pass to get rid of (or "clone out", if you will) the dust spots. I avoid using the healing tool - I find that it can introduce artifacts, especially in areas that are only subtlely different from one another.

... sorry that I wasn't clear enough.
« Last Edit: February 16, 2007, 15:04 by sharply_done »

« Reply #8 on: February 16, 2007, 21:57 »
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I found another way to get rid of the dust spot problem: I bought an Olympus E-1 a couple of months ago. Fantastic camera, weather sealed body as well as lenses, and no dust whatsoever   ;D

« Reply #9 on: February 16, 2007, 22:12 »
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Good on ya!

Man, it would be great to be rid of dust forever.

Dust is my scourge. I one made the mistake of changing lenses with fleece gloves on - I couldn't believe the amount of fibers that jumped onto the sensor in the short time it took to swap lenses.

On the upside, I've become the fastest clone-tooler west o' the Pacos!

« Reply #10 on: February 17, 2007, 04:25 »
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To get rid of dust spots i clean my sensor.  :)

« Reply #11 on: February 17, 2007, 16:28 »
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I take my camera to a professional camera cleaning service.  Yes, it costs money.  But the camera comes back within a day completely clean.  The first time I did this I found the sensor was better than new.

« Reply #12 on: February 17, 2007, 22:22 »
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LOL
great thread!

shoot it the best you can and only get rid of noise for shutterstock...and only after they reject it for noise!


 

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