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Occasional Contributor
Posts: 12
Registered: ‎11-25-2013

Raw Image Visibility and size.

I have read several articles in which it is claimed that RAW images are not visible unless converted. However, in DPP software that comes with our EOS camera, we can see raw images even before conversion. If these are the +JPEG images  the camera produces how come we process RAW images based on the JPEG images we see? There must be something  I am missing. Besides, I noticed that RAW image size is quite smaller than the converted TIFF image size How is this?

Esteemed Contributor
Posts: 4,952
Registered: ‎06-25-2014

Re: Raw Image Visibility and size.


@Epicuros wrote:

I have read several articles in which it is claimed that RAW images are not visible unless converted. However, in DPP software that comes with our EOS camera, we can see raw images even before conversion. If these are the +JPEG images  the camera produces how come we process RAW images based on the JPEG images we see? There must be something  I am missing. Besides, I noticed that RAW image size is quite smaller than the converted TIFF image size How is this?


The commonly repeated assertion that a RAW image can't be displayed is something of an overstatement. It can't be processed by the usual display algorithms, but software can obviously be written to display it, as in DPP. Also, a RAW file customarily contains a small embedded JPEG rendition of itself. Its resolution is too low to be useful in a photo editor, but it can be used to provide a thumbnail display by cataloguing programs like the Windows Explorer.

 

A TIFF image is large because, unlike a JPEG, it's designed to be "lossless" and very general. TIFF is probably less efficient than it could be, but it's used so little these days that its inefficiency can usually be overlooked.

Bob
Philadelphia, Pennsylvania USA
Occasional Contributor
Posts: 12
Registered: ‎11-25-2013

Re: Raw Image Visibility and size.

Thanks for your prompt response Bob. I understand that most often than not a JPEG thumbnail accompanies the RAW file, but when you process RAW images on DPP you have the possibllity of a full screen image and the editing steps are immediately visible. If we were working on a JPEG image, even one with little loss, how valid would be the processing if what we see is a JPEG and not an original RAW image? I find this difficult to conceive... Further, I quite understand why a TIFF file is larger than a JPEG file, but what I don't understand is why it is bigger than a RAW file... I am not a software nerd, so I may be writing nonsense, but we, old guns will never be fully conversant with new tech. :-)
Esteemed Contributor
Posts: 4,952
Registered: ‎06-25-2014

Re: Raw Image Visibility and size.

[ Edited ]

@Epicuros wrote:
Thanks for your prompt response Bob. I understand that most often than not a JPEG thumbnail accompanies the RAW file, but when you process RAW images on DPP you have the possibllity of a full screen image and the editing steps are immediately visible. If we were working on a JPEG image, even one with little loss, how valid would be the processing if what we see is a JPEG and not an original RAW image? I find this difficult to conceive... Further, I quite understand why a TIFF file is larger than a JPEG file, but what I don't understand is why it is bigger than a RAW file... I am not a software nerd, so I may be writing nonsense, but we, old guns will never be fully conversant with new tech. :-)

Don't say that! I'm probably older than you are, and I'm not about to sell us old geezers short.  Smiley Wink

 

The reason a TIFF is larger than a RAW file is that a RAW file records the data exactly as it came from the camera, while TIFF has to deal with the fact that its data could have come from any of a variety of RAW formats and must be recorded in a camera-independent form. One consequence is that it must account for higher resolution (and potentially longer data items) than current cameras normally use.

 

As for editing, keep in mind that when you're editing a picture, you're just looking at a collection of dots on a screen. Whether the underlying image on which you're working is a JPEG, TIFF, RAW file, or something conceptually different is obscured by implementation detail. The photo editor has to try to ensure that "what you see is what you get", but how it does that is ultimately unimportant. If the final result is, say, a JPEG, then that JPEG must be (assuming that the display or print algorithm does its job correctly) a faithful representation of what the camera saw. As long as that's the case, what goes on in the editor itself is like making sausage: you can't see how it's done and probably wouldn't want to.

 

So when someone tells you that "what you see (when you're editing a RAW file) is actually a JPEG", that assumes that the editor converts the RAW image to JPEG and turns it over to a JPEG processing module for display. With some editors, maybe that is what happens, but it's not a given. And it doesn't matter anyway, as long as what is done is good enough to satisfy your eyes.

Bob
Philadelphia, Pennsylvania USA
Esteemed Contributor
Posts: 3,308
Registered: ‎02-17-2016

Re: Raw Image Visibility and size.

Actually, the reason the Tiff is larger is that it takes the bayer image from the sensor and converts it to Full RGB. So the RAW file has only 1 color channel, 1/4 red, 1/4 blue and 1/4 green, while the Tiff has 3 full color channels.

Esteemed Contributor
Posts: 4,952
Registered: ‎06-25-2014

Re: Raw Image Visibility and size.


@kvbarkley wrote:

Actually, the reason the Tiff is larger is that it takes the bayer image from the sensor and converts it to Full RGB. So the RAW file has only 1 color channel, 1/4 red, 1/4 blue and 1/4 green, while the Tiff has 3 full color channels.


Just what I said! (Although you stated it much more accurately and succinctly.)  Smiley Happy

Bob
Philadelphia, Pennsylvania USA
Esteemed Contributor
Posts: 3,308
Registered: ‎02-17-2016

Re: Raw Image Visibility and size.

I messed up anyway! 8^)

 

Should be 1/2 green.

Occasional Contributor
Posts: 12
Registered: ‎11-25-2013

Re: Raw Image Visibility and size.

Thank you all. The combined answers shed quite a bit of light on my confused brain! Q-)
VIP
Posts: 11,100
Registered: ‎12-07-2012

Re: Raw Image Visibility and size.

[ Edited ]

The big thing to remember is compression.  Raw is not compressed.  Jpegs are, sometimes severely.  It is this compression which actually deletes info from the file to make it smaller that concerns us.  Less info = less ability to edit.

Another thing to remember no camera company can agree on exactly what is a Raw file is so no standard exists.  Not even among models from the same company!

 

A Raw file is not effected by any edit you do. Jpegs are permanently altered when edited or even saved for that mater. A Raw file contains two thing besides the raw data.  One is a metadata tag and a jpeg for viewing on the cameras LCD.  These two tag along files are what is used by your post editor to give you a viewable photo.  It is not the actual Raw file however.  It does give you a starting point for your edits but you notice you don't save a Raw, you save something else.  A tiff or jpg, etc.  Plus the metadata tag is updated.

 

BTW, guys, I use tiff all the time.Lots of good stuff in a tiff.

EOS 1DX and 1D Mk IV, even less and less other stuff.
Occasional Contributor
Posts: 12
Registered: ‎11-25-2013

Re: Raw Image Visibility and size.

Thanks for your response ebiggs1
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