How Do You Do It and Does It Work?

[briansquibb]

Re: How Do You Do It and Does It Work?

Just as a point of interest, if the files were not compressed how can they all be different sizes? They are different because of the compression. Even ISO changes the file sizes as ISO noise doesn't compress well (much more random). If there was no compression, every file would be the same size (apart from things like sRAW which reduce resolution too).

The size of the files also varies according to the information kept in them. RAW has significantly more information for example it keeps the orginal photo as shot as well as any modifications - this is why you can revert to the shot photo. JPEG and TIF does not hold this information. Having been a computer programmer for 40 years I can assure you that no file is equal to another unless it is a straight copy - and that applies here. as clearly a TIFF file is not the same as a JPEG which is not the same as a RAW

The CPN article explains file compression more eloquently than I can http://cpn.canon-europe.com/content/education/infobank/image_compression/lossless_and_lossy_compression.do.

I understand what Stephen is saying and agree with him except for the line about RAW not being compressed - it is, but a lossless compression - simillar to computer ZIP files

[EOS_Jim]

Re: How Do You Do It and Does It Work?

Hi Jim

I'm not sure why you choose to pick an argument - I had got the idea that this was a particularly friendly forum. I can assure you that my knowledge of digital imaging is fairly sound (I won the 2007 Guru award from the American National Association of Photoshop Professionals) amongst other things - and digital photography is my profession.

I was genuinely trying to be helpful here - But I'm fair too busy to get involved in disagreements for no good reason, so I'll leave you to your forum.

Stephen

Stephen sorry if that is the way it comes across. There is absolutely no argument from me - only a fact that hopefuilly I proved to you - I thought you would have appreciated knowing this?

I only advised that RAW is a compressed file and you disagreed and I corrected you? Is it not better that we get the correct information when discussing? It would not be fair to leave it with a wrong point.

Whilst having a qualification is to be greatly admired, it does not mean you will always be right when questioned on something.....

Perhaps the way I write comes across wrongly and I don't mean it to be - I just type before reading a lot of the time :)

I posted an image below showing the uncompressed size of a Canon ES5D MkII file. 60.2Mb

[EOS_Jim]

Re: How Do You Do It and Does It Work?

The size of the files also varies according to the information kept in them. RAW has significantly more information for example it keeps the orginal photo as shot as well as any modifications - this is why you can revert to the shot photo. JPEG and TIF does not hold this information. Having been a computer programmer for 40 years I can assure you that no file is equal to another unless it is a straight copy - and that applies here. as clearly a TIFF file is not the same as a JPEG which is not the same as a RAW

The CPN article explains file compression more eloquently than I can http://cpn.canon-europe.com/content/education/infobank/image_compression/lossless_and_lossy_compression.do.

I understand what Stephen is saying and agree with him except for the line about RAW not being compressed - it is, but a lossless compression - simillar to computer ZIP files

Hi Brian
Yes that was the link I posted - there is another oine on the site too but I only posted one.

Yes absolutely the compressed RAW fle size does vary a lot in size depending on what information is in the file. If you have shot with a lot of clear blue sky the size will be a lot less due to the compression algorithm. But what does not change is the Uncompressed file size as that relates to the number of pixels in the image x 3 (for an 8bit RGB file). I approximated at 63Mb but photoshop shows the actual uncompressed size as 60.2Mb (due to the odd number (1024) that makes up 1Mb) ALL my canon EOS5D MkII files are exactly the same - when exported (without any cropping obviously as that would chang ethe file size).
(see attached - the uncompressed size is shown down on the left of the image next to the zoom level)

THe file sizes are the same because every pixel holds the same type of information - a known RGB value - that is what makes up the 24bit colour.

I understand Stephen's thoughts too - I was just pointing out that the the thought that the RAW was not compressed was incorrect and that has a knockon effect to the other points. Absolutely a lossless compression.

[EOS_Jim]

Re: How Do You Do It and Does It Work?

Yes I’m talking about 16 bit Jim, that’s how I end up larger files, you’re right the 40D will make circa 30 mb 8bit tiffs.
Ultimately I have to convert my 16bit tiff to 8 bit to enable conversion to a jpg

My main point is that is one of the simplest points in their submission guidelines to get one’s head around, and yet there always seems to be much confusing debate. I wouldn’t be surprised if all confusing debate has actually put people off submitting.

Best we get the details from the horse’s mouth by looking at the submission guidelines, if anyone still has a problem/question with file sizes they only have to ask .

http://www.alamy.com/contributor/help/prepare-images.asp

Trev

Hi Trev a 16bit uncompressed file from a 5DII will have a size of 120.3Mb in photoshop - that number is fixed for all files (without cropping)

A 40D uncompressed 16bit Tif file will be 57.7Mb so tight! And as noted the 8bity tif file will be 28.8Mb in size.

I never use 16bit files as I don't require them but nice to know I can if I had to. I don't really see any difference in the final output although the histogram does look better with a 16bit file.

[Trevoreast]

Re: How Do You Do It and Does It Work?

Jim I've edited 5Dmk2 16bit tiffs on my PC, I noticed I was getting the progress bar appearing a lot in photoshop when making changes.
I would have to upgrade my PC or get a new one if I got a 5Dmk2

The 350D is listed in thier reccommended camera list,I assume the images need some upscaling ?

Trev

[EOS_Jim]

Re: How Do You Do It and Does It Work?

Jim I've edited 5Dmk2 16bit tiffs on my PC, I noticed I was getting the progress bar appearing a lot in photoshop when making changes.
I would have to upgrade my PC or get a new one if I got a 5Dmk2

The 350D is listed in thier reccommended camera list,I assume the images need some upscaling ?

Trev

Yes they would need to be upscaled. Easy to work out the sizes. 8bit tif = 3456x2304x3 and a 16bit tif = 3456x2304x6

So even a 16bit tif falls just shy of 50Mb

[EOS_Jim]

Re: How Do You Do It and Does It Work?

The size of the files also varies according to the information kept in them. RAW has significantly more information for example it keeps the orginal photo as shot as well as any modifications - this is why you can revert to the shot photo.

Brian the RAW file itself actually doesn't hold that info either. The RAW file itself doesn't change in size with any modifications becuse these modificaions to the RAW file are controlled by a second fiile - either an XMP sidecar file or by the software's database file. That holds all the info required like metadata, crop info and any other changes you make to the sliders in ACR or Lightroom (or whatever program you choose).

JPG and Tif are actially dealt with in the same way although the level of control is not the same. You can also amend a tif or jpg in ACR or Lightroom and the file can be reverted back to the original file you edit (not necessarily the original file) becuse the jpg/tif you use to open is never physically changed - only the xmp / database file changes according to the coices you make and these are applied when you open the file in Lr or ACR.

When you open the raw/tif/jpg file, the linked xmp is read by Lr and the changes are shown and these can be amended as many times as you like and all that will change is the sidecar file. This also allows you to create "virtual" copies of the file you opened and all that is created is a second or third (or more) XMP file/database record. So you can have 1 file but have many different "virtual" versions.

Cheers
JD

[briansquibb]

Re: How Do You Do It and Does It Work?

JPG and Tif are actially dealt with in the same way although the level of control is not the same. You can also amend a tif or jpg in ACR or Lightroom and the file can be reverted back to the original file you edit (not necessarily the original file) becuse the jpg/tif you use to open is never physically changed - only the xmp / database file changes according to the coices you make and these are applied when you open the file in Lr or ACR.

I never use LR or ACR so that is a function of the editing program not the file format. Just like Elements saves it in a PSD - but save the jpeg and it isn't reversable.

No XMP files in my RAW folders - could be that I only use DPP to handle the files. When you edit a RAW file in DPP ony a copy of the metadata is edited and saved in the CR2 file - the original is left untouched to allow reversion. The CR2 file format provides the extra fields to allow for this.

CR2 files have a signigicant amount of metadata that can be edited.

The Adobe uitilies only access the origninal fields - to verify this open DPP and change the image to monochrome. Then open it in your Adobe utility and you will spot that it is still in colour. Go back to DPP and it is still in monochrome. You will also be able to spot that the CR2 file date has changed to that when you changed it to monochrome - there are no extra files created. As you say - the extra files are created by the Adobe utilities.

I have looked in detail at the format of the RAW CR2 files as I was going to write some post processing programs for it. However Canon dont publicise the formats - so it is very difficult to maintain such a program. So after a few prototypes I stopped

[EOS_Jim]

Re: How Do You Do It and Does It Work?

I was going to edit that but just double checked what I said and I provided a little misinfo there myself! Apparently with jpg/tif files the sidecar is not created and the XMP metadata is written into the files in the location specified for that data.

[EOS_Jim]

Re: How Do You Do It and Does It Work?

I never use LR or ACR so that is a function of the editing program not the file format

Hi Brian interesting and i did a little more research and it seems that DPP saves the info into the RAW file itself - exactly the same idea just a different implementation. The changes are very minimal and just a few kb at most. the main changes to RAW size are the amount of compression achievable.

You can use a sidecar in DPP though (vrd recipie files) although these are implemented differently from ACR/Lr in that you need to load the file once the image is open. That allows also multiple virtual copies - just a slightly slower way to work but same job.

i always thought raw files weer not editable but obviously canon know how to do that.

[briansquibb]

Re: How Do You Do It and Does It Work?

Jim - was adding more data to my response when you wrote the replies

[EOS_Jim]

Re: How Do You Do It and Does It Work?

Jim - was adding more data to my response when you wrote the replies

i remember I didn't know what the sidecar files were when I first had lightroom so I deleted them...... Only to find I lost about 1000 edits :)

[APOY1998]

Re: How Do You Do It and Does It Work?

To get photographers to take there picture!!!

[Desmond]

Re: How Do You Do It and Does It Work?

I read your offer after reading it i reached at the decision it is so nice but it is a bit difficult for me!
i have no experience of the photography!

[colin C]

Re: How Do You Do It and Does It Work?

So why do soccer players take their shirts off when celebrating??????...

Nothing wrong with that .............. ladies football? ............ get my drift?

Colin