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Author Topic: OOPS on ISO  (Read 6197 times)
Stephenaweiss
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« on: June 06, 2006, 12:32:52 AM »
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My son borrowed my Nikon D200 (for the last time!) and set the ISO to 400. The next day I took a photograph I like, but assumed the ISO was 100. Now when I convert to black and white and try to go up a bit on contrast, the clouds break up into pixels.

Is there any way to fix this?
thanks, stephen
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Dmitry
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« Reply #1 on: June 06, 2006, 03:17:20 AM »
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See a variant:

I did it in PSP9

Histogram adjustment(Gamma - 1.4) + unsharp mask (radius 2) + saturation correction
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« Reply #2 on: June 06, 2006, 06:03:56 AM »
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My son borrowed my Nikon D200 (for the last time!) and set the ISO to 400. The next day I took a photograph I like, but assumed the ISO was 100. Now when I convert to black and white and try to go up a bit on contrast, the clouds break up into pixels.

Is there any way to fix this?
thanks, stephen
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Stephen, Please don't stop your son from using your camera.    

Just my opinion - but I think the way to fix this would be that if he looked after the camera, I think it would be better to let him enjoy taking photographs, and you check the settings before you take your photo.    
Julie
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John Sheehy
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« Reply #3 on: June 06, 2006, 10:10:23 AM »
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Is there any way to fix this?
thanks, stephen
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It's too late to do anything but filter out the noise.  The sky is easy; you just mask it and run a median filter on it.  The detailed areas, however, will get softer if you filter the noise.

Other than say "check the settings before you use the camera", I would also suggest that you learn to "expose to the right".  Check your histogram after a shot like that; the clouds should be almost touching the right edge in JPEG, or start clipping a little if you're shooting in RAW and using a converter that is good at preserving highlights.  I see you used a gamma of +1.4 in post-processing.  This indicates under-exposure in the camera.

I haven't studied noise characteristics of Nikons as much, but with Canon DSLRs, a stop of under-exposure causes more noise than a stop higher ISO.  It really isn't the ISO setting, per se, that is the root of noise, but the amount of light hitting the sensor, as is determined in each shot by the lighting, and the f-stop and shutter speed.  There is at least a couple stops of exposure lattitude in each shot, where the image looks like it is in the ballpark for proper exposure.  Those two stops vary the noise by 4x, whereas two stops of ISO difference might vary the noise by only 2x, or less.  It is therefore essential that you learn to expose as high as possible without clipping desired highlights, to minimize noise.

Two people could go out and shoot all day at ISO 400 with your camera, I think, and one could have clean pictures, and another noisy.  The one who leans toward under-exposure (or even standard exposure) will always get more noise.
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Richowens
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« Reply #4 on: June 06, 2006, 12:20:42 PM »
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Stephen,

Thank you for the opportunity to work on such a nice clean image. Even at 200% there is almost NO noise anywhere, even in the shadows. At 300%, pixelization is just barely becoming evident in the clouds, and this is after it was resized to 240 dpi and cropped.

I used only a couple of curve layers to open the shadows a little and steepen the contrast curve. I did this on two different layers,left both at full opacity, then converted to b&w using an action from Digital Outback Photo with an orange filter.

It was sharpened with PK Sharpener capture on medium edge setting and creative with luminance setting, dark contour about 30% and light contour about 80%.

I fouund nothing wrong with the capture. I consistently use ISO 400 on my D70 and have to use noise reduction on only about 20% of my shots. In my opinion this is cleaner than the D70 and of course it is sharper due to higher resolution.
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Richowens
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« Reply #5 on: June 06, 2006, 12:21:46 PM »
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Stephen,

Thank you for the opportunity to work on such a nice clean image. Even at 200% there is almost NO noise anywhere, even in the shadows. At 300%, pixelization is just barely becoming evident in the clouds, and this is after it was resized to 240 dpi and cropped.

I used only a couple of curve layers to open the shadows a little and steepen the contrast curve. I did this on two different layers,left both at full opacity, then converted to b&w using an action from Digital Outback Photo with an orange filter.

It was sharpened with PK Sharpener capture on medium edge setting and creative with luminance setting, dark contour about 30% and light contour about 80%.

I fouund nothing wrong with the capture. I consistently use ISO 400 on my D70 and have to use noise reduction on only about 20% of my shots. In my opinion this is cleaner than the D70 and of course it is sharper due to higher resolution.
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Stephenaweiss
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« Reply #6 on: June 06, 2006, 09:19:39 PM »
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Thank you to everyone. I was under the impression that about 60% of image data from a sensor is the top approximately 10% of the lightest portion of the image, so that the more you expose for the highlights, there is exponentially less data/detail in the shadows. So the teaching I have heard is to adjust down one or two f stops to keep more detail in shadows and mid tones, and adjust later for your highlights...

thanks, s
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John Sheehy
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« Reply #7 on: June 06, 2006, 09:58:03 PM »
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Thank you to everyone. I was under the impression that about 60% of image data from a sensor is the top approximately 10% of the lightest portion of the image, so that the more you expose for the highlights, there is exponentially less data/detail in the shadows. So the teaching I have heard is to adjust down one or two f stops to keep more detail in shadows and mid tones, and adjust later for your highlights...

thanks, s
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No; that's not how digital exposure works.  At the RAW level, the general rule is the higher the exposure, the better for all tonal ranges, with the possible danger of clipping highlights.  There is no saturation benefit, or any other, in under-exposure of a tonal range.  The only reason you might under-expose is to avoid clipping.  Now, if you shoot JPEGs, the camera will clip at a lower level than the RAW data, and it may compress flatten the highlights and make them pale.  Generally, if you use normal or high contrast for the JPEGs, you will get unflattened highlights, but if you use lower contrast, the clipping point will get higher but the extra highlights will be flattened (a shoulder).

Digital photography, in its present state, is not very kind to under-exposure.  Many people are under-exposing their digital images, though, even people who were experts at exposing film, but digital is not like film.
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Richowens
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« Reply #8 on: June 06, 2006, 10:18:38 PM »
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I apologise for the double posts and lack of image.

When I tried to attach the image today, the board posted only what I had written until then. I could not edit either post nor add another reply.

If this works, I'll know the problem is not at my end.

Anyway, I found the image well exposed, without blown highlights or blocked shadows.

Still unable to attach an image.

Rich
« Last Edit: June 06, 2006, 10:19:54 PM by Richowens » Logged

Stephenaweiss
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« Reply #9 on: June 06, 2006, 10:53:39 PM »
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Quote from: John Sheehy,Jun 6 2006, 06:58 PM
No; that's not how digital exposure works.  At the RAW level, the general rule is the higher the exposure, the better for all tonal ranges]

John, I think I am getting stuck on language. I think we are saying the same. I will bracket by taking a light reading, then taking a second shot with the lens open one larger F stop, ie: 4 instead of 5.6. By doing this I am giving up some detail ( I believe clipping) in the hi-lights, and hopefully gaining them in the shadow and mid-tone.

Do I have that right? I guess I still think in film terms.

Do you have a good thread or reference for me to read more on?

thanks for the time, s
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Stephenaweiss
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« Reply #10 on: June 06, 2006, 11:40:44 PM »
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Here is my second attempt, have noticed the clouds are staying in better definition. Lightroom and Convert to B & W pro are what I used. [attachment=662:attachment]
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John Sheehy
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« Reply #11 on: June 07, 2006, 11:00:52 AM »
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John, I think I am getting stuck on language. I think we are saying the same. I will bracket by taking a light reading, then taking a second shot with the lens open one larger F stop, ie: 4 instead of 5.6. By doing this I am giving up some detail ( I believe clipping) in the hi-lights, and hopefully gaining them in the shadow and mid-tone.

Do I have that right? I guess I still think in film terms.
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That's about right, except that there may actually be no clipping by opening to 4, or even 2.8, depending on the contrast and key of the scene.

I don't know how true it is with the Nikons, but I know that with the more recent Canons, going to a higher ISO while keeping the f-stop at 5.6 will work, too.  For probably all digitals that do RAW, exposing as high as possible at a given ISO without clipping gives the least noise, because you are increasing the signal-to-noise ratio.  You must have a workflow, however, that preserves the highlights well, to take advantage.  RAW is a big plus for this.  Depending on the camera, you may or may not get a higher *absolute* signal-to-noise ratio at higher ISOs, like the recents Canons tend to do.  In other words, If I set my 20D to ISO 1600, and expose a scene at +2 EC in manual mode, and then take successive shots with the ISO halving for each shot (1600 -> 800 -> ... -> 100), and then use EC in a RAW converter to make them all equally bright, the ISO 1600 image will have less noise, but more potential for clipping.  The ISO 100 image will have the greatest highlight range, but will be the noisiest (not subtly, either; quite dramatically).  With a camera that behaves like this, if you are working in a paradigm where f-stop and shutter speed are your primary considerations, then the highest ISO that doesn't clip desired highlights will give the least noise.  Noise is only proportional to ISO in auto-modes, or in manual mode where constant metering offsets are used, as the ISO then varies the *absolute* sensor exposure.
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John Sheehy
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« Reply #12 on: June 07, 2006, 11:05:34 AM »
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John, I think I am getting stuck on language. I think we are saying the same.
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Your "adjust down"  of the "f-stop" is what I misunderstood.  I thought you meant "stop down" rather than "open up".
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francofit
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« Reply #13 on: June 07, 2006, 10:25:28 PM »
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...
Do you have a good thread or reference for me to read more on?
...

Michael's article here.
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Franco
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