ISO and Highlight Protection

smoke665

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I'm trying to learn, but something I read earlier has me confused. I've been experimenting with Pixel Shift and Macro trying to get the sharpest possible detail from highlight to shadow. According to the article, "exposing with an ISO of 640-2000 strikes the best balance between highlight protection and low image noise. If one ventures outside this range, exposure needs to be much more precisely controlled, and has much less margin for error. When in doubt, ISO 800 is a good start, but the optimal setting will also depend on image content. For example, lower contrast scenes generally don’t need as much highlight protection, and may therefore benefit more from ISO settings as low as ISO 320". The reasoning being that "the best way to shift the balance between noise and clipping protection is with the ISO setting. Although ISO doesn’t actually change the raw image data, it does change how the image is displayed, since it shifts which portions of the scene are mapped to middle gray". I've been shooting at ISO's in the 100 to 200 range, assuming that this was the best, am I wrong???
 
I think you are right. I rarely go higher than 200 which has never produced visible noise for me. I took an image this morning at 800 and reshot it because of all the noise.

It is time for you you to investigate HDR. It combines images at different exposures so that you can extend the dynamic range limitations of cameras. I do HDR with Photoshop but, if you don't have photoshop, you can acquire dedicated HDR applications. My Nikon D7100 camera, has built in HDR which works reasonable well but certainly shy of what can be done with Photoshop. HDR is the answer for you, not shooting at high ISO settings when they aren't necessary.
 
Just because someone has written something doesn't mean it is worth reading. Particularly on the Interweb! I use ISO 100 almost all the time and have no problems with either noise or highlights.
 
which exact camera are they referring to ?
different model cameras have differing ISO results.
ie, there's no way I'd compare ISO of a D40 to a D5 with a blanket statement.

If you are referring to a scene that has a very wide dynamic range beyond your sensor's (and supporting processing chips) ability then HDR (as mentioned) may be the way to go.
 
It is time for you you to investigate HDR

I have both in camera (up to 5 images) and post up to 9. .My current question is more to the use of Pixel Shift and then combining those into an HDR. First shots look promising, though it seems there is more tendency to blow the speculars and lose detail in the really dark colors. The problem becomes even more pronounced when the images are stacked.
 
which exact camera are they referring to ?
different model cameras have differing ISO results.
ie, there's no way I'd compare ISO of a D40 to a D5 with a blanket statement.

If you are referring to a scene that has a very wide dynamic range beyond your sensor's (and supporting processing chips) ability then HDR (as mentioned) may be the way to go.

In this case I'm using a Pentax K3 II with Pixel Shift. Despite the fact that it's been out for awhile there's not a whole lot of information on use. This is one of the images I got last night. All my attempts to improve seemed to be at the expense of something else. Guess it won't cost me anything to experiment with higher ISO to rule out that possibility.

IMGP0730 -1- test 1 pixel.jpg
 
The small amount of blown highlights in that picture do not matter at all. At the size I get on my tablet, there is no noise visible. So not a lot to worry about regarding exposure.
 
From reading, I thought the Pixel Shift is a kind of HDR
The flower petals, being fabric, see to have a bunch of tiny bright light reflections which you may be thinking is noise.
 
Fabric flowers? I was wondering about the strange texture.
 
I'm trying to learn, but something I read earlier has me confused. I've been experimenting with Pixel Shift and Macro trying to get the sharpest possible detail from highlight to shadow. According to the article, "exposing with an ISO of 640-2000 strikes the best balance between highlight protection and low image noise. If one ventures outside this range, exposure needs to be much more precisely controlled, and has much less margin for error. When in doubt, ISO 800 is a good start, but the optimal setting will also depend on image content. For example, lower contrast scenes generally don’t need as much highlight protection, and may therefore benefit more from ISO settings as low as ISO 320". The reasoning being that "the best way to shift the balance between noise and clipping protection is with the ISO setting. Although ISO doesn’t actually change the raw image data, it does change how the image is displayed, since it shifts which portions of the scene are mapped to middle gray". I've been shooting at ISO's in the 100 to 200 range, assuming that this was the best, am I wrong???

I don't use a Pentax with Pixel Shift but from what I've read about it there's no special requirement to do anything different with ISO compared with taking a single shot. Some of what you quote above from an article is startling and certainly sounds like it was written by someone who doesn't understand how a digital camera functions.

"the best way to shift the balance between noise and clipping protection is with the ISO setting. Although ISO doesn’t actually change the raw image data, it does change how the image is displayed, since it shifts which portions of the scene are mapped to middle gray". Major false there: ISO really does change the raw image data. Any increase in ISO records less data in the raw file -- never a good thing.

"For example, lower contrast scenes generally don’t need as much highlight protection, and may therefore benefit more from ISO settings as low as ISO 320". What the BLEEP!!! That statement of course suggests that higher contrast scenes needing more highlight protection then benefit from higher ISO settings!!! NEVER!! NEVER!!! ABSOLUTELY NEVER!!!!

Somebody you're reading doesn't understand how a camera works unless I'm missing some huge strange function in Pixel Shift that nobody is talking about.

Best image quality results from exposure at base ISO. Increasing ISO above base uses less of sensor's recording capacity = less data recorded = less is less.

Joe
 
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From reading, I thought the Pixel Shift is a kind of HDR
The flower petals, being fabric, see to have a bunch of tiny bright light reflections which you may be thinking is noise.

In a way it is HDR on steroids in that a pixel shift image is a compilation of four images each shifted by one pixel. In essence you get the equivalent of 96 megapixel from a 24 megapixel sensor. The flowers are fabric, and I suspect the white dots are reflected light from off the surface of the fabric.
 
Somebody you're reading doesn't understand how a camera works unless I'm missing some huge strange function in Pixel Shift that nobody is talking about.

I can't disagree with you, but sadly I haven't been able to find much in depth information on using Pixel Shift. As I understand from Pentax some of the "noise" from higher ISO on the Bayer Sensor is actually reduced by the Pixel Shift ability to read higher details in the shadows. Which, makes me curious to explore it further.
 
Somebody you're reading doesn't understand how a camera works unless I'm missing some huge strange function in Pixel Shift that nobody is talking about.

I can't disagree with you, but sadly I haven't been able to find much in depth information on using Pixel Shift. As I understand from Pentax some of the "noise" from higher ISO on the Bayer Sensor is actually reduced by the Pixel Shift ability to read higher details in the shadows. Which, makes me curious to explore it further.

That makes sense since each pixel is being exposed through one of the green filters. But that just means that a base ISO exposure is all that much the better and will of course still be better than an underexposure that results from raising the ISO. When the K3 (or any pixel shift design) saves a raw file it saves all 4 (or more) separate exposures. Those four exposures are combined in processing avoiding normal demosaicing.

Joe
 
. When the K3 (or any pixel shift design) saves a raw file it saves all 4 (or more) separate exposures. Those four exposures are combined in processing avoiding

I haven't figured out where the four images go, but they aren't saved separate on the card. Only the one processed image is saved
 
. When the K3 (or any pixel shift design) saves a raw file it saves all 4 (or more) separate exposures. Those four exposures are combined in processing avoiding

I haven't figured out where the four images go, but they aren't saved separate on the card. Only the one processed image is saved

The raw file that is saved when pixel shift is used encapsulates the four exposures; that's why it's so much bigger than a normal Pentax DNG. That's also why it requires special processing -- most raw converters can't process it. Otherwise the JPEG the camera creates is a normal JPEG.

Using pixel shift it's not necessary to determine the color for a pixel in the photo by using an interpolation algorithm (demosaic) that examines surrounding pixels. Instead the color for a pixel is determined by combining the data in the four separate exposures. No interpolation means a more exact and accurate result with the one major liability that the camera and subject must be immobile.

Otherwise handling of ISO and exposure should be no different than without the pixel shift tech engaged.

Joe
 

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