Quality v Quality

u8myufo

u8myufo

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Rich
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I was wondering is there any image loss as such between cropping a Raw file or the same file but cropped after it has had a straight conversion to JPEG :shrug: Hard facts needed here guy`s :D not a, I think it does or I think it does not:lol:
Thanks
 
Forbiddenbiker said:
You can't crop a raw file...its not an image file. :)
Click to expand...

Well that was the impression I was under FB, untill it was pointed out to me that within DPP if you double click a Raw image you can start the trimming tool which allows you to crop, when saved it is stilla Raw file, hence this is why I asked the question :thumbs:
 
Oh is that right, interesting, useful for minimising I suppose.

...It must be just a cropped section of the sensors recordings then, so directly comparable to how many pixels are left in the crop.

I am just guessing sorry :D ...but as a Raw file is just the data of the actual collections of each colour pot on the sensor, a true crop of that can only be the same collections, just less of them.


:shrug:




.
 
I'll admit to having no knowledge of DPP, but I thought you couln't edit a raw file in any way. PS will only allow you to save changes to a different format, and LR just keeps a meta file describing your edits - does it use one of those methods?
 
Forbiddenbiker said:
Oh is that right, interesting, useful for minimising I suppose.

...It must be just a cropped section of the sensors recordings then, so directly comparable to how many pixels are left in the crop.

I am just guessing sorry :D ...but as a Raw file is just the data of the actual collections of each colour pot on the sensor, a true crop of that can only be the same collections, just less of them.


:shrug:




.
Click to expand...

:shrug::shrug: Here is a screen grab,first is original raw and second is cropped raw

raw800x600.jpg


cropraw800x600.jpg
 
Don t know about the quaility by cropping before or after just think it can be useful to crop the raw file and have a better look at it in case its not worth bothering with cos you can even sharpen before you convert to see if its worth doing DPP can be useful
 
Couldn't you just zoom in though...same thing isn't it?

u8myufo said:
:shrug::shrug: Here is a screen grab,first is original raw and second is cropped raw
Click to expand...

Nice shot. I dunno either, but I notice the file name of the new cropped Raw is not a proper file name, more of an extension for DPP to open it as a crop perhaps ....of course where not looking at the Raw file in these shots (that’s not possible) ...where looking at a generated JPG or Tiff file....

Can you open the new cropped Raw in any other Raw software? ..I'm guessing you can't.

Im sticking to my original thoughts at the mo ...qualities the same, against the amount of pixles left.
 
in DPP when you crop you can go back to the image later and change the crop or even remove it. The DPP "crop" is just a marker to say what part of the image you are going to output to jpeg or print, it does not remove any of the original CR2 raw image.
 
Forbiddenbiker said:
Couldn't you just zoom in though...same thing isn't it?



Nice shot. I dunno either, but I notice the file name of the new cropped Raw is not a proper file name, more of an extension for DPP to open it as a crop perhaps ....of course where not looking at the Raw file in these shots (that’s not possible) ...where looking at a generated JPG or Tiff file....

Can you open the new cropped Raw in any other Raw software? ..I'm guessing you can't.

Im sticking to my original thoughts at the mo ...qualities the same, against the amount of pixles left.
Click to expand...

:thumbs: Not too sure what you mean by saying it isnt a proper file name FB :shrug: They are both a cr2 image what am I missing? And yes you are right about the crop, if I save it itjust saves the whole image again :thumbs:
 
A raw file cropped and saved as a raw file is virtually unchanged, if you crop it in half, the file size is still pretty much the same because all the original data is still contained within it, you can make it look as if its been cropped, but it hasn't because the bit you didn't want isn't discarded.
This is why you can't crop a raw.

I can't see a difference between a cropped raw saved as jpg and a cropped jpg..:)
 
No difference - either way you are throwing away pixels.
 
Are you saying that DPP can save a new file to your hard drive with a cr2 extension and that it will be different to the cr2 file you started with? ie if you open it with a different raw viewer/editor the two files will show different things - cropped and uncropped image?
 
joxby said:
A raw file cropped and saved as a raw file is virtually unchanged, if you crop it in half, the file size is still pretty much the same because all the original data is still contained within it, you can make it look as if its been cropped, but it hasn't because the bit you didn't want isn't discarded.
This is why you can't crop a raw.

I can't see a difference between a cropped raw saved as jpg and a cropped jpg..:)
Click to expand...

As you state you cannot "save as" a RAW file. You can export as an image file like jpg, tif, psd etc but not as a RAW.

Also you can convert to dng but you convert the whole image - not a crop.
 
Forbiddenbiker said:
Ah gottcha ...There both called IMG_2793. ..the crop one has an star 'after' the end of the file name, same name though, so its likely to be the same file.

A saved crop would have a different name see.

:thumbs:

Hope you get an answer, all extra possible detail is always good to know how and all that.
Click to expand...

the * shown in most Windows apps after the filename means "you've made changes to this document, but have not saved it". you will see it pretty much in every Windows app :]
 
Thanks all for your answers, just to clarify for anybody else then :)

The first screen shot shows the original file on the left and the file on the right is what I thought was the saved crop, although I renamed it, the extension was added but the picture is identical, however in the second screen shot you will notice that when viewed in DPP the embedded crop frame is showing.

example1.jpg


example2.jpg
 
u8myufo said:
Thanks all for your answers, just to clarify for anybody else then :)

The first screen shot shows the original file on the left and the file on the right is what I thought was the saved crop, although I renamed it, the extension was added but the picture is identical, however in the second screen shot you will notice that when viewed in DPP the embedded crop frame is showing.

example1.jpg


example2.jpg
Click to expand...

THe robin fil is the exact same file as yor original - as you say, just renamed if they are on the same disk,delete one osave space. ust makesure they are backe up elsewher :)
 
u8myufo said:
I was wondering is there any image loss as such between cropping a Raw file or the same file but cropped after it has had a straight conversion to JPEG :shrug: Hard facts needed here guy`s :D not a, I think it does or I think it does not:lol:
Thanks
Click to expand...

Two things happen when you convert from raw to JPEG....

1. Bit depth gets reduced from 12 or 14 bits to 8 bits per channel, so you lose the finest subtleties in tonal gradation;

2. The file is further compressed to discard "unimportant" information, but you can compress to different degrees, some of which look fine and some of which just look plain awful.

So, when you crop a raw file and then output to JPEG you only "suffer" one round of image damaging compression. If you were to output a full res file to JPEG and then open that JPEG file, crop it and then save again you would risk a further loss in quality from the second compress/save operation.

Now, with that in mind I believe you can get "lossless" cropping, which does not recompress the file on the second save, but does literally simply crop off the surplus pixels. This would work in the same way as "lossless" rotation. However, I suspect there are certain rules that need to be adhered to, such as pixel dimensions must be in multiples of 8, and, of course, your cropping software must implement lossless cropping as an option.

Irfanview can perform lossless cropping - http://www.downloadatoz.com/manual/ir/irfanview/hlp_jpg_lossless_crop.htm. As for other software, I have no idea.
 
tdodd said:
Two things happen when you convert from raw to JPEG....

1. Bit depth gets reduced from 12 or 14 bits to 8 bits per channel, so you lose the finest subtleties in tonal gradation;

2. The file is further compressed to discard "unimportant" information, but you can compress to different degrees, some of which look fine and some of which just look plain awful.

So, when you crop a raw file and then output to JPEG you only "suffer" one round of image damaging compression. If you were to output a full res file to JPEG and then open that JPEG file, crop it and then save again you would risk a further loss in quality from the second compress/save operation.

Now, with that in mind I believe you can get "lossless" cropping, which does not recompress the file on the second save, but does literally simply crop off the surplus pixels. This would work in the same way as "lossless" rotation. However, I suspect there are certain rules that need to be adhered to, such as pixel dimensions must be in multiples of 8, and, of course, your cropping software must implement lossless cropping as an option.

Irfanview can perform lossless cropping - http://www.downloadatoz.com/manual/ir/irfanview/hlp_jpg_lossless_crop.htm. As for other software, I have no idea.
Click to expand...

Thanks Tim :thumbs: That has explained a lot to me, and you earn yourself a bonus for explaining it in a language I understand :D
 
recrudesce said:
the * shown in most Windows apps after the filename means "you've made changes to this document, but have not saved it". you will see it pretty much in every Windows app :]
Click to expand...

Thought as much. :thumbs:

Chaz Photos said:
You can make a crop frome a RAW file in ACR and it imports it into Photoshop as a 16 bit TIFF in my case
Click to expand...

Ah can it, what’s ACR? adobe...

Do you think the quality of the tiff is better than the quality of a larger tiff cropped and saved to the same?

I guess its one layer less processing...so less losses? ...unless you got lossless cropping.
 
Forbiddenbiker said:
Thought as much. :thumbs:



Ah can it, what’s ACR? adobe...

Do you think the quality of the tiff is better than the quality of a larger tiff cropped and saved to the same?

I guess its one layer less processing...so less losses? ...unless you got lossless cropping.
Click to expand...


ACR = Adobe Camera Raw - you can use any raw conerter for this (I use Lightroom)

Makes no difference but I would generally criop the RAW image (cause it's easier in my workflow). If you export to a tif, this is a lossless compression, so cropping after the export should not reduce the file size.

There is no such thing as lossless when you crop though - to crop means generally to reduce the size and therefore throw away data. I know you can increase an image size using the crop tool too though (but that's not really cropping (resizing).
 
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