Ad
Ad
Ad
Pages: [1] 2 »   Bottom of Page
Print
Author Topic: High ISO or push in the raw converter?  (Read 12302 times)
David Watson
Sr. Member
****
Offline Offline

Posts: 395


WWW
« on: December 10, 2011, 07:03:34 AM »
ReplyReply

I would be interested to know if better results can be obtained by using a lower ISO in camera and pushing the exposure in ACR or LR.  Which one produces a cleaner image and less noise?

Superficially it seems to me that the computer, with is greater processing power and more complex (?) software, ought to be making a better job than relying on the camera's limited processing capacity.

Logged

David Watson ARPS
ErikKaffehr
Sr. Member
****
Offline Offline

Posts: 7676


WWW
« Reply #1 on: December 10, 2011, 07:22:01 AM »
ReplyReply

Hi!

On some cameras pushing ISO helps by increasing amplification before feeding the signal to the ADCs. This is pure amplification and it does not involve processing. All Canon models have this behavior. Cameras based on the latest CMOS-designs from Sony will probably benefit little as they don't have pre-amps.

The processing ability in the camera is quite impressive, BTW. My MacPro consuming 200 W with four cores can convert one image/second using all eight thread. My Sony Alpha converts 5 image/second and operates on a small battery.

Best regards
Erik


I would be interested to know if better results can be obtained by using a lower ISO in camera and pushing the exposure in ACR or LR.  Which one produces a cleaner image and less noise?

Superficially it seems to me that the computer, with is greater processing power and more complex (?) software, ought to be making a better job than relying on the camera's limited processing capacity.


Logged

mouse
Full Member
***
Offline Offline

Posts: 171


« Reply #2 on: December 10, 2011, 05:21:02 PM »
ReplyReply

I would be interested to know if better results can be obtained by using a lower ISO in camera and pushing the exposure in ACR or LR.  Which one produces a cleaner image and less noise?


From your question I assume that (for whatever reason) you do not have the option of resolving the under-exposure problem using shutter speed and/or aperture.  To expand on Erik's reply, increasing the ISO up to about 1600 (in many but not all) cameras will reduce noise and thus allow a cleaner image.  Note that doing so comes at the price of reducing the dynamic range (see the graph in Erik's post).
Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5163


« Reply #3 on: December 10, 2011, 05:23:22 PM »
ReplyReply

I would be interested to know if better results can be obtained by using a lower ISO in camera and pushing the exposure in ACR or LR.  Which one produces a cleaner image and less noise?
The one possible advantage I have heard of for the more complicated route of using a lower ISO speed setting and then compensating in post-processing is avoiding blown-out highlights in scenes that have highlights well above your intended "midtone placement".

The two possible advantages of setting the ISO speed at the level appropriate for your intended tonal placement are (1) extra analog amplification before ADC, which can improve shadow noise, and (2) avoiding that extra post-processing step of pushing.

By the way, it seems common that cameras to some extent avoid applying excessive analog gain in producing RAW data anyway: beyond a certain level, higher ISO settings do not increase analog gain, but only (a) apply further digital domain amplification during in-camera RAW conversion, (which is trivial; just bit-shifting), and (b) put information into RAW files suggesting that RAW conversion software on the computer do likewise.

But evidence in recent threads indicates that advantage (1) only applies with some cameras, like Canons (and some older models with inadequate ADC's), and even then only up to about two or three stops above the base ISO speed, IIRC.

So unless a scene gives reason to worry about extreme highlights (liked dimly lit interiors with brightly lit windows, or other mixtures of substantial shadows with brightly lit parts), you might as well do the simple thing: adjust the ISO speed so that the levels come out as you want them without need for "digital push processing".

Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5163


« Reply #4 on: December 10, 2011, 05:26:59 PM »
ReplyReply

... increasing the ISO up to about 1600 (in many but not all) cameras will reduce noise and thus allow a cleaner image.  Note that doing so comes at the price of reducing the dynamic range (see the graph in Erik's post).
Higher ISO speed setting will not decrease dynamic range so long as it does not cause clipping of highlights; so long as the highlights stay in range, reducing the noise floor will indeed increase dynamic range, in the practical sense of range from highest recorded signal level to shadow noise level.
Logged
Guillermo Luijk
Sr. Member
****
Offline Offline

Posts: 1291



WWW
« Reply #5 on: December 10, 2011, 05:31:50 PM »
ReplyReply

Superficially it seems to me that the computer, with is greater processing power and more complex (?) software, ought to be making a better job than relying on the camera's limited processing capacity.

The impressive processing power needed to push ISO in software is as follows:

Let 1067 be a given RAW level in some pixel as captured by the camera. Now the user pushes exposure by 1 stop in his RAW developer. The computer makes the following ultrasophisticated calculus: 1067 * 2 equals 2134. End.
Logged

deejjjaaaa
Sr. Member
****
Offline Offline

Posts: 966



« Reply #6 on: December 10, 2011, 06:46:24 PM »
ReplyReply

The impressive processing power needed to push ISO in software is as follows:

Let 1067 be a given RAW level in some pixel as captured by the camera. Now the user pushes exposure by 1 stop in his RAW developer. The computer makes the following ultrasophisticated calculus: 1067 * 2 equals 2134. End.


except ACR/LR do not work w/ raw data when you operate any sliders in their UI - they convert immediately to prophoto colorspace w/ gamma 1 and push will be w/ that data.
Logged
mouse
Full Member
***
Offline Offline

Posts: 171


« Reply #7 on: December 10, 2011, 08:31:20 PM »
ReplyReply

Higher ISO speed setting will not decrease dynamic range so long as it does not cause clipping of highlights; so long as the highlights stay in range, reducing the noise floor will indeed increase dynamic range, in the practical sense of range from highest recorded signal level to shadow noise level.

Based on my (admittedly limited) understanding, reducing the noise floor could theoretically increase dynamic range only if the highlight clipping point is not reduced to the same extent.  I doubt this is ever the case.  As long as the highlights remain within range, increasing the ISO is effective in reducing the noise floor, but it simultaneously lowers (by as much or more) the point at which the highlights will no longer be in range.  That is my concept of dynamic range.
Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5163


« Reply #8 on: December 10, 2011, 08:54:22 PM »
ReplyReply

Mouse,

    Let us not debate the definition of dynamic range (which in photography is often mangled relative to its well-established engineering meaning) and just look at image quality results. So long as the ISO speed is low enough that no pixel suffers from clipping, then the upper end of the range is in practice at exactly the same level, but the noise floor is lower, an undeniable improvement with no downsidemfor this particular image. Any unused highlight headroom above the brightest highlights is irrelevant to the quality of this particular image.

The difference is like measuring something that you know is about eight inches long with a yard-stick instead of a foot-ruler and claiming an advantage of triple the dynamic range just because the yard-stick has 360 divisions of 1/10 inch compared to 120 such divisions on the foot-ruler. And if the foot-ruler is instead accurate to 1/20 inch (half the measurement noise), its result will be better, though it still has only 240 divisions, so less "length DR".
Logged
mouse
Full Member
***
Offline Offline

Posts: 171


« Reply #9 on: December 11, 2011, 12:58:59 AM »
ReplyReply

Mouse,

    Let us not debate the definition of dynamic range (which in photography is often mangled relative to its well-established engineering meaning) and just look at image quality results. So long as the ISO speed is low enough that no pixel suffers from clipping, then the upper end of the range is in practice at exactly the same level, but the noise floor is lower, an undeniable improvement with no downsidemfor this particular image. Any unused highlight headroom above the brightest highlights is irrelevant to the quality of this particular image.



Well I certainly do not quarrel with your basic conclusion concerning image quality.  It simply restates the reasoning that underlies ETTR; increase the exposure short of clipping desired highlights and thereby lift the shadows that much above the noise floor.  And if, for whatever reason, you cannot do this with shutter speed and or aperture, you can achieve the same effect by increasing ISO (up to a point, and only with some cameras).

Nevertheless I will stick to my initial concept of dynamic range; the total number of stops (or whatever unit you choose) between the brightest highlight that can be captured and the deepest shadow that registers above the noise floor (how far above is subject to debate).  This concept applies regardless of the luminance range of the particular scene I am photographing, which may be less than, equal to or greater than the dynamic range of the camera.

regards/m
Logged
Guillermo Luijk
Sr. Member
****
Offline Offline

Posts: 1291



WWW
« Reply #10 on: December 11, 2011, 04:49:41 AM »
ReplyReply

I will stick to my initial concept of dynamic range; the total number of stops (or whatever unit you choose) between the brightest highlight that can be captured and the deepest shadow that registers above the noise floor (how far above is subject to debate).  This concept applies regardless of the luminance range of the particular scene I am photographing, which may be less than, equal to or greater than the dynamic range of the camera.

Both of you are right, but saying different things. Basically JBL is talking about the DR that can be captured in a particular scene as long as highlights are not clipped, even if ISO is pushed. You are talking more generally, about the maximum DR than can be captured for a given ISO in optimal conditions, i.e. when perfect ETTR can be achieved at every ISO.

If you can achieve ETTR at base ISO, that will be the ideal situation where more DR can be captured (cleanest shadows), so base ISO provides max DR. In that context, lower ISOs always permit to capture a higher DR (that is why DxO DR plots are always decreasing).

But if you cannot achieve ETTR at base ISO with your aperture/shutter, i.e. there is still some highlight headroom, you will be able to increase captured DR (more in some cameras, less in others) by pushing ISO until ETTR is achieved. In that situation, pushing ISO can actually increase captured DR (that is why ISO can be useful to the RAW shooter).

Regards
« Last Edit: December 11, 2011, 04:54:40 AM by Guillermo Luijk » Logged

hjulenissen
Sr. Member
****
Offline Offline

Posts: 1683


« Reply #11 on: December 11, 2011, 05:57:23 AM »
ReplyReply

If you in one way or another rely on in-camera JPEG, then increasing in-camera ISO makes a lot of sense.

-h
Logged
hjulenissen
Sr. Member
****
Offline Offline

Posts: 1683


« Reply #12 on: December 11, 2011, 06:03:18 AM »
ReplyReply

The processing ability in the camera is quite impressive, BTW. My MacPro consuming 200 W with four cores can convert one image/second using all eight thread. My Sony Alpha converts 5 image/second and operates on a small battery.
First, you mac probably consumes power that is unrelated to image processing.

Second, the algorithms are different.

Third, in-camera algorithms are probably highly optimized for the platform (perhaps even implemented in hardware). Software running on your mac is probably more general and with many layers of security, generalization etc between the transistors and the image processing algorithm.

Your raw developer may do operations that usually benefit camera files, but have little or no benefit for your Sony Alpha.

But despite my objections, I agree with you, it is impressive what can be done and still be able to take a lot of images before running out of battery. Wonder what they could do if they made a raw-only camera.

-h
Logged
RFPhotography
Guest
« Reply #13 on: December 11, 2011, 07:44:15 AM »
ReplyReply

except ACR/LR do not work w/ raw data when you operate any sliders in their UI - they convert immediately to prophoto colorspace w/ gamma 1 and push will be w/ that data.

LR, yes.  ACR, no.  ACR uses the colour space (and associated gamma) of whatever is chosen as the output space in the Workflow Options at the bottom of the screen.

What commercial converters do allow you to work directly on the raw data?  All are rendered in some form on screen. 
Logged
deejjjaaaa
Sr. Member
****
Offline Offline

Posts: 966



« Reply #14 on: December 11, 2011, 09:54:56 AM »
ReplyReply

LR, yes.  ACR, no.  ACR uses the colour space (and associated gamma) of whatever is chosen as the output space in the Workflow Options at the bottom of the screen.

Whatever "is chosen as the output space" is exactly that - output space - internally it is prophoto and there is some math there in ACR/LR between the raw data and whatever is actually pushed by the exposure slider.

Eric Chan, for example (one of many) = "...the internal reference scene-referred space in Camera Raw & LR is indeed RIMM (ProPhoto linear)..."

For some other non core operations (but not the exposure correction) there might even further (errors, errors) conversion (prophoto/linear -> probably some modded form of the output space selected).

Eric Chan, for example (one of many) =  "...The actual color space used for an operation depends on the routine (e.g., noise reduction, clarity, fill light, HSL adjustments, etc.)....", "...ACR/LR does perform internal color transforms as needed to carry out its various image processing routines (e.g., noise reduction, vibrance, etc.). However, this is all done internally and has no real connection to the user-specified color space of the rendered output file (e.g., sRGB, Adobe RGB, etc.)...."

/ added - one more curious detail found = Eric Chan :: "ACR does use L*a*b* for some internal color difference estimates, e.g., for auto-calculated masks." /


but the first thing ACR/LR do - is to get rid of the raw data by converting that to its internal space - once and only once.


What commercial converters do allow you to work directly on the raw data?    

Why do you try to limit yourself to commercial software ?
« Last Edit: December 11, 2011, 10:05:31 AM by deejjjaaaa » Logged
RFPhotography
Guest
« Reply #15 on: December 11, 2011, 10:25:42 AM »
ReplyReply

Why commercial software?  Because that's what the vast majority of people are going to use.  Simple.  Take commercial out of the question then.  What conversion software doesn't render the image on screen according to some colour space and gamma assumptions?

Then why does the on screen rendering change in ACR when the output space is changed in the Workflow Options?  If it were solely based on RIMM, it should act like LR and a change in the output space should be just that and not affect what's seen on screen till after the image is opened into PS, shouldn't it?
Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5163


« Reply #16 on: December 11, 2011, 10:48:45 AM »
ReplyReply

Both of you are right, but saying different things. Basically JBL is talking about the DR that can be captured in a particular scene as long as highlights are not clipped, even if ISO is pushed. You are talking more generally, about the maximum DR than can be captured for a given ISO in optimal conditions, i.e. when perfect ETTR can be achieved at every ISO.
Agreed completely: my only interest in this thread is how to choose settings (ISO speed, aperture, shutter speed, stops of push or pull in post-processing) to get the best results with a particular scene. I would be happy if most photographers stopped using (and more often abusing) electronic engineering jargon like "dynamic range" and instead used established, practical, relevant photographic concepts and measures like subject brightness range, blown/burnt-out highlights, and visible shadow noise. Or otherwise be clear about how a particular jargon term and measurement relates to photographic objectives, not just spec. sheet pissing contests.

The one case I see where it could be better to use a lower ISO speed that adds unused highlight headroom is when there is lots of uncertainty about highlights, such as when you will have to make a sequence of shots with variable lighting and without time to adjust ISO settings or meter for each shot.  The good news is that cameras are starting to offer modes where the ISO speed is one of the parameters automatically adjusted on the basis of metering, and sensors are offering that light metering at millions of points in the scene.
Logged
deejjjaaaa
Sr. Member
****
Offline Offline

Posts: 966



« Reply #17 on: December 11, 2011, 11:25:37 AM »
ReplyReply

Why commercial software?  Because that's what the vast majority of people are going to use.  Simple.

vast majority does not care about in camera ISO vs push in raw converter


Take commercial out of the question then.  What conversion software doesn't render the image on screen according to some colour space and gamma assumptions?

no, the note was not about that - the note was the exposure correction in ACR/LR does not operate on the per channel raw data, but instead on the data which is received from the raw data by applying some math first... some raw converters do operate on the raw data in this case - google and you shall find.

Then why does the on screen rendering change in ACR when the output space is changed in the Workflow Options?

because the end result of ACR work is some data in "the output space", so you shall see that difference...

If it were solely based on RIMM, it should act like LR and a change in the output space should be just that and not affect what's seen on screen till after the image is opened into PS, shouldn't it?

I do not own LR - but in LR you shall see that too.

PS:

If

it is not "If" - it is from Eric Chan.
Logged
deejjjaaaa
Sr. Member
****
Offline Offline

Posts: 966



« Reply #18 on: December 11, 2011, 11:29:01 AM »
ReplyReply

The good news is that cameras are starting to offer modes where the ISO speed is one of the parameters automatically adjusted on the basis of metering, and sensors are offering that light metering at millions of points in the scene.

do they know what you are exposing for ?
Logged
RFPhotography
Guest
« Reply #19 on: December 11, 2011, 11:37:30 AM »
ReplyReply

vast majority does not care about in camera ISO vs push in raw converter
Such as?  Why be so obtuse with 'google and you shall find'?  If you've got something better, then just say what it is.  Do all other raw conversion applications work the way you describe?  Some?  Which?  If all or most then why bother with the 'why restrict to commercial software?' comment?  It's pretty clear you have an axe to grind against Adobe/Eric.  Whatever the reason for that is your issue. 

Quote
no, the note was not about that - the note was the exposure correction in ACR/LR does not operate on the per channel raw data, but instead on the data which is received from the raw data by applying some math first
Fine.  That wasn't completely clear in your statements.

Quote
I do not own LR - but in LR you shall see that too.
Don't believe so because the way LR works is that the output colour space is only applied on Export of the image to the rendered file format.  There's no ability (as far as I'm aware) to change the onscreen view to something other than Melissa for colour and sRGB for the histogram (I believe that's the way it works) in LR.
Logged
Pages: [1] 2 »   Top of Page
Print
Jump to:  

Ad
Ad
Ad