Pages: [1]   Go Down

Author Topic: Different Size Raw Files--Two Questions  (Read 7517 times)

MICHAEL YOUNG

  • Newbie
  • *
  • Offline Offline
  • Posts: 5
Different Size Raw Files--Two Questions
« on: November 19, 2013, 05:26:14 PM »

Hello,

I've lurked at LL for years but never posted.

I have a couple of questions regarding RAW files.

1) What is going on with the data when one selects the different sizes that are available? For instance, my camera lets me choose Large, Medium or Small.  The large is 20MP and the medium is 11MP and so on.  How does that work?

2) Does selection of a RAW file size smaller than the maximum affect noise?

Thanks in Advance because I know someone here can address this :)

Mike
 
Logged

louoates

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 836
    • Lou Oates Photography
Re: Different Size Raw Files--Two Questions
« Reply #1 on: November 19, 2013, 08:22:27 PM »

I think raw is raw, with no size selection. My Canon has 2 memory card slots. One I have set for raw, the other for L (for large) jpgs. Maybe your L selection only applies if you want your card saving jpgs.
Logged

MICHAEL YOUNG

  • Newbie
  • *
  • Offline Offline
  • Posts: 5
Re: Different Size Raw Files--Two Questions
« Reply #2 on: November 20, 2013, 11:57:33 AM »

Thank you for that reply; I do appreciate it.

I was hoping to drill down to a different level though and I think the phrasing of my original question(s) may not be specific enough.

So,

If I have a full size sensor that inherently is 20MP and I decide to choose a smaller RAW output, say 11MP, then how is the camera selecting those 11MP?  What information is it discarding?    Somewhere, somehow the camera is saying "goodbye" to millions of pixels.  How is it doing that?
« Last Edit: November 20, 2013, 11:59:27 AM by MICHAEL YOUNG »
Logged

Isaac

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 3128
Re: Different Size Raw Files--Two Questions
« Reply #3 on: November 20, 2013, 12:57:51 PM »

If I have a full size sensor that inherently is 20MP and I decide to choose a smaller RAW output, say 11MP...

Do you have a camera that allows you to choose a smaller RAW output? Which camera?
Logged

jjj

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 4738
    • http://www.futtfuttfuttphotography.com
Re: Different Size Raw Files--Two Questions
« Reply #4 on: November 20, 2013, 01:20:32 PM »

sRAW is an option of shooting raw files that are not as big as the usual raw full size option.
Canon offer it, there are three sizes of Raw on my 5DII body. I forget the pixel dimensions off hand as I never use it. But could be handy for say timelapse.
Logged
Tradition is the Backbone of the Spineless.   Futt Futt Futt Photography

jjj

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 4738
    • http://www.futtfuttfuttphotography.com
Re: Different Size Raw Files--Two Questions
« Reply #5 on: November 20, 2013, 01:22:34 PM »

Here's some info from Canon about it. Though their examples of where it could be useful are pretty dumb. e.g. a wedding photographer using it for candid shots.
« Last Edit: November 20, 2013, 01:25:48 PM by jjj »
Logged
Tradition is the Backbone of the Spineless.   Futt Futt Futt Photography

MICHAEL YOUNG

  • Newbie
  • *
  • Offline Offline
  • Posts: 5
Re: Different Size Raw Files--Two Questions
« Reply #6 on: November 20, 2013, 02:02:49 PM »

Thank you so much.

I had searched around in Canon/Rudy Winston's columns but I guess I didn't do a very good job.

My main interest in how the smaller files are created or truncated is/was wondering if it is/was done "on chip" where I imagine it might improve noise performance or whether it was accomplished via some algorithm after a capture that involved the entire chip.  Silly I guess but if you don't ask you don't learn. :)

The camera is a 6D. 

I can't especially see a use for the smaller file sizes for the types of things I do but thought that if noise was affected in a positive way that it might offer a way to bump the ISO for some night shots of the Milky Way, etc.  Thus the curiosity.

Thank you again for the link.

Mike
Logged

jjj

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 4738
    • http://www.futtfuttfuttphotography.com
Re: Different Size Raw Files--Two Questions
« Reply #7 on: November 20, 2013, 02:15:42 PM »

For things like astrophotography reducing resolution will very likely be detrimental compared to any potential noise reduction, once both images are enlarged to same size.
Logged
Tradition is the Backbone of the Spineless.   Futt Futt Futt Photography

Ellis Vener

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2108
    • http://www.ellisvener.com
Re: Different Size Raw Files--Two Questions
« Reply #8 on: November 22, 2013, 01:43:47 PM »

It is done while the initial capture is being processed.  I believe the process is called "binning". Data fro mthe full size capture is being, for want ofa better word, averaged. to create the smaller, and potentially  lower resolution, file. If Canon (or Nikon, et. al.) uses an algorithm to protect the differences in areas areas with a high level of detail  while averaging the values of the  areas of relatively similar tone, I don't know. I suspect they are not. I suspect that what is going on is that if you have a hypothetical  5x5 grid ( 25 pixels) an sRAW algorithm  s averages those values to produce a 4x4 (16), 3x3 (9) or 2x2 (4) pixel grid in the sRAW file. If that is the case yes you are losing real world detail.
Logged
Ellis Vener
http://www.ellisvener.com
Creating photographs for advertising, corporate and industrial clients since 1984.

Schewe

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 5986
    • http:www.schewephoto.com
Re: Different Size Raw Files--Two Questions
« Reply #9 on: November 22, 2013, 07:06:17 PM »

Ellis is correct...it's called binning and it's done on the digital to analog chip. Also note it's a blunt force reduction in capture size, it results in a demosiaced file (to bin the original capture and down sample, it needs to run the demosiacing on the raw file) which limits the flexibility of the resulting small raw file. There are situations where this binned raw file would be useful if you don't need the full rez file but, image quality is NOT a major factor in it's favor. You would be better off capturing the full raw file size and downsampling after the fact in your software of choice.

Point of fact, I "think" the way Canon does it is using a bi-linear algorithm which tends toward chattering along diagonal edges...which degrades IQ.
Logged

MICHAEL YOUNG

  • Newbie
  • *
  • Offline Offline
  • Posts: 5
Re: Different Size Raw Files--Two Questions
« Reply #10 on: November 23, 2013, 06:32:49 PM »

Thanks everyone for the replies, Ellis & jjj, it's what I needed to know.
« Last Edit: November 24, 2013, 11:41:49 AM by MICHAEL YOUNG »
Logged

MICHAEL YOUNG

  • Newbie
  • *
  • Offline Offline
  • Posts: 5
Re: Different Size Raw Files--Two Questions
« Reply #12 on: November 24, 2013, 11:53:00 AM »

I am back to offer thanks a second time, specifically for the introduction to the word "binning."  Google is bringing up some interesting 'this and thats' on the topic, a couple of which coincide with my noise reduction ideas.  To be quite certain, I'll need to do more reading but it does look like there's some noise reduction benefit out there.  When the time comes that I can say with certainty, I'll return with the findings.

Again, many thanks to each and every respondent.

Mike
Logged

jjj

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 4738
    • http://www.futtfuttfuttphotography.com
Re: Different Size Raw Files--Two Questions
« Reply #13 on: November 25, 2013, 06:52:33 AM »

You are unlikely to get any benefits from binning as you'll your noise will be less noticeable in say a 30x20 print from the larger file than one from a smaller low res file that has had to have been enlarged way more. Noise reduction in software can be quite good if used carefully too.
Oh and comparing such things at 100% on screen can be quite misleading, as that 100% view will be way smaller with less noise issues on a print with a high res shot.
Logged
Tradition is the Backbone of the Spineless.   Futt Futt Futt Photography

Ed Blagden

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 491
    • http://www.flickr.com/photos/ed-blagden
Re: Different Size Raw Files--Two Questions
« Reply #14 on: January 01, 2014, 08:13:50 AM »

The only advantage of sRAW I can think of is if you are doing continuous burst shooting (eg of a bird in flight) and want a longer burst before the buffer fills up.

I just tried this: continuous shooting at the 3 different settings on my 5Dii.  How many shots before the buffer filled up as follows:

RAW (21mp): 14 Shots
sRAW1 (10mp): 20 Shots
sRAW2 (5mp): 29 Shots.

So there you go.  Not sure if this is of any use whatsoever in the real world.

Logged
Visit my Flickr page

PeterAit

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2546
    • Peter Aitken Photographs
Re: Different Size Raw Files--Two Questions
« Reply #15 on: January 01, 2014, 08:17:32 AM »

Check your manual. Perhaps, like my D600, you can choose "native" RAW (largest) or lossless compressed RAW (smaller). Or between 12 bit and 14 bit RAW? The former choice would not affect noise, the latter might have a small effect (I am not sure about that, however).
Logged
Peter
"Photographic technique is a means to an end, never the end itself."
View my web page
View my Facebook page

bjanes

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 3207
Re: Different Size Raw Files--Two Questions
« Reply #16 on: January 01, 2014, 08:55:39 AM »

Ellis is correct...it's called binning and it's done on the digital to analog chip. Also note it's a blunt force reduction in capture size, it results in a demosiaced file (to bin the original capture and down sample, it needs to run the demosiacing on the raw file) which limits the flexibility of the resulting small raw file. There are situations where this binned raw file would be useful if you don't need the full rez file but, image quality is NOT a major factor in it's favor. You would be better off capturing the full raw file size and downsampling after the fact in your software of choice.

Point of fact, I "think" the way Canon does it is using a bi-linear algorithm which tends toward chattering along diagonal edges...which degrades IQ.

Pixel binning with Bayer CFA sensors is problematic as explained in this Phase One paper. These problems have been addressed with Phase One's Sensor+ technology, which is proprietary and patented. If Canon is using pixel binning, how do they address these problems?

Bill
Logged

Petrus

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 860
Re: Different Size Raw Files--Two Questions
« Reply #17 on: January 19, 2014, 05:31:01 AM »

I have used the small RAW option a few times when I knew the pictures were destined for the net (no big sizes needed) and I needed to fit more shots on one CF card (cards were smaller a few years back). If big sizes are not needed this also shortens the process times a bit also.

Now with LR it is easy to conveniently output any size JPEGs even from full size RAW files, and the speed advantage is not big with smaller RAWs (and there is always danger of forgetting to reset the camera back to full size RAW), so I do not use the small RAWs anymore. Only 14 bit loslessly compressed for me.
Logged
Pages: [1]   Go Up