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RAW vs. cRAW

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romke View Drop Down
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Post Options Post Options   Quote romke Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 08:35
there may be another reason to prefer raw to craw.

when shooting images in continuous mode the rate of image capture (fps) may well slow down somewhat because compressing will also take some time and processor capacity.

at the same time when using craw it will take longer to fill the buffer completely, so you might be able to get more shots in a sequence.

has anybody ever made a comparison between the two types of shooting when using max fps?

it may also be that not every raw converter around that can handle raw files will also be capable of handling craw files.

 



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Shatun View Drop Down
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Post Options Post Options   Quote Shatun Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 09:52
That was a hot discussion when A700 was released. The main fuel was statement from sony in FAQ that cRAW has same quality. But sony removed it after some days of our discussions. At that time I considered to by A700 and it was interesting to me to understand this so I will remind my research results. As source for my research I used dcraw sources and first I analyzed the format itself. cRAW uses small block with data and then compress them. In best case cRAW uses 11 bits but not 12 so with cRAW we are loosing 1 bit in any case. Second if we have big contrast in green, or red, or blue, OR we have color close to blue or red then we could loose more bits with maximum up to 5. But from other side I have feeling that in such cases those bits are not very significant. Any way for me personally I decided to stack with DNG.

Second I have extended dcraw with special analize mode to generate images based on cRAW and displays the loss information. At the moment when I did my research there was almost no cRAWs in internet, so I did just one test.

Original image


Result. As brighter color as more bits we are loosing. The color itself show the affected color.


In general I could say that idea from Sony was really smart. The compression ration is high but in comparation with lossless compression like Haffman the image is resistant against media corruption. Also this compression requires very less CPU and memory usage.

One from many threads about this is here:
Page 5 with my post

Edited by Shatun - 16 August 2010 at 19:50
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Peekayoh View Drop Down
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Post Options Post Options   Quote Peekayoh Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 13:09
I have nothing to contribute to the debate on whether or not the loss in cRAW is significant but, as with most things, whether or not to choose cRAW really comes down to one of cost, cost of CF/MS cards and cost of data storage.

With HDD prices down to L90 for 2 Terra bytes and with the cost/MB halving almost every year, the cost of data storage is pretty much a non issue.
The cost of flash memory, on the other hand, is rather more significant.

I have 32MB of CF cards which I found a bit limiting for my A700 plus, only 2x8MB cards are 300x (45MB/sec), the rest are old and slooow.
For my newly acquired A900 and contemplating a 10 day trip, I figured I needed another 2x32MB cards to be safe. Ouch! Nearly L400 and out of the question having just blown the budget (and a bit more) on the A900 + CZ16-35mm.

Anyway, to cut a long story short, I decided on a L160, "Nexto" 320GB portable backup device.
Basically it's a Battery powered, 320GB, 21" SATA hard drive and in size is, unsurprisingly, similar to a standard 21" ext. drive but about twice as thick.
The NexTo LiPol battery does 60GB between recharges and if thats not enough you can buy an external battery which is good for another 80GB. Charging is done via USB or a provided mains PSU.

The device takes CF cards or a whole bunch of Memory stick/SD variants via a second 4in1 slot or via USB.
A microprocessor and eeprom software allows for several functions but I'm only concerned with one (for now) which is, automatic transfer of images from the CF card with data verification. This function is selectable via a simple Menu System on the front LCD.

In use, nothing could be more simple, plug in the CF card and the NexTo recognises the card, creates a new folder, copies the images, verifies the copies by comparing them with the originals and, if all Ok, deletes the CF card ready for it to go back in camera. The whole process takes less than six minutes for my 8GB Sandisk. A different folder name is generated every time you put in a CF (or other) card.

On the trip, the 2x8GB Sandisks were more than adequate for a day's shooting and I didn't need to recharge the NexTo.
At home it connects to my PC for file transfer via eSATA (60MB/sec) or you can use USB.

All I need now is a second NexTo drive so I have a backup in case of failure.
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frankieg View Drop Down
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Post Options Post Options   Quote frankieg Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 13:21
As far as I'm concerned if this group has to search that hard and no one has ever come up with a real life example under any circumstances, where a difference between the two formats is visible in the final image, then the format is effectively lossless while not numerically lossless.

My challenge to the group is... Produce the conditions you beleive will SHOW the loss in an image under studio conditions then publish the findings. Or should I say show us the images. That should be a simple task.

Let me see if I can explain why I believe it is photographically lossless. Well I can't really so I won't even try. I did it in my mind and I believe me so that's good enough for me.

BTW Shatun, thanks for your post and the link to the thread.
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Post Options Post Options   Quote GrahamB Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 13:35
Originally posted by Peekayoh Peekayoh wrote:



I have 32MB of CF cards which I found a bit limiting for my A700 plus, only 2x8MB cards are 300x (45MB/sec), the rest are old and slooow.
For my newly acquired A900 and contemplating a 10 day trip, I figured I needed another 2x32MB cards to be safe. Ouch! Nearly L400 and out of the question having just blown the budget (and a bit more) on the A900 + CZ16-35mm.


I have 3 16GB Transcend 400x cards, and just purchased a 32GB card for use in my a850. In the US, the 16GB sells for $60 and the 32 for $110. I checked Amazon UK link. The prices are a bit higher, but still 1/2 of your quote.

The Transcend 400x exceeds the a900's 5fps requirements and comes with a lifetime warranty. I've used Transcend almost exclusively since picking up 4GB 133x cards for my KM 7D. 8GB 266x worked well in my a700 and now 400x 16 and 32GB for the full frame. 5+ years, multiple cards and cameras and approaching 100,000 actuations without a single hiccup lets me recommend Transcend without reservation.

Graham
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Post Options Post Options   Quote Shatun Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 14:06
Originally posted by frankieg frankieg wrote:

[/QUOTE]

You are welcome :) In general for me it is kind of mental issue :) I do know as mathematic and informatic that there is a loss and I would not live with it until I decide is it acceptable for me or not. I missed upgrade to sony alpha and I still KM D7D user so I still have time. Now I am very happy with DNG. They use acceptable comparation ratio which is true lossless. For sure there are could be other issues like lossing not standardized meta information or hotpixel remapping but I can live with that. Any way I hope one day I will by new alpha and then I will make a decision.
 



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Octupi View Drop Down
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Post Options Post Options   Quote Octupi Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 14:52
Originally posted by Fuzzphoto Fuzzphoto wrote:

If the difference is both negligable and invisible, why use larger files?


Exactly my opinion as well. I shoot everything (paid jobs) in cRAW and have never been sorry.

Before I made the switch to cRAW I did many comparison shots, outside, inside studio, etc and I could never find a difference in the image after processing. cRAW give me 50% more card space and when shooting a wedding or a sports team, that extra space is quite useful.
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Mark L View Drop Down
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Post Options Post Options   Quote Mark L Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 15:06
Same as Octupi. If what little difference there is cannot be detected be either me or my clients I am not going to worry about it.
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Post Options Post Options   Quote roweraay Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 15:37
Originally posted by Fuzzphoto Fuzzphoto wrote:

If the difference is both negligable and invisible, why use larger files?


Contrarily, if the cRAW is truly loss-less for all intents and purposes, then why would Sony even provide the totally loss-less/unmanipulated RAW in their professional models ?    To fill up the CF-cards faster ?

PS: Nikon also does this. They call it NEF (RAW) and cNEF (cRAW). Nikon only offers full loss-less NEF in their models D300 and higher (in other words, professional models). In all other consumer level models, they don't even attempt to provide NEF and only provides cNEF, because providing the larger NEF (especially at higher 5FPS etc) requires a higher specced data pipeline architecture, than the smaller cNEF files.

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Post Options Post Options   Quote Maxxuman Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 16:14
Originally posted by frankieg frankieg wrote:

As far as I'm concerned if this group has to search that hard and no one has ever come up with a real life example under any circumstances, where a difference between the two formats is visible in the final image, then the format is effectively lossless while not numerically lossless.

My challenge to the group is... Produce the conditions you beleive will SHOW the loss in an image under studio conditions then publish the findings. Or should I say show us the images. That should be a simple task.

That pretty much echoes my view. I always shoot cRAW on my A700 and have seen nothing to convince me I should change. I will keep watch for any future developments that suggest software support for the format may be dropped, but I expect that won't happen for some years and there will then be options available to allow continued use of them.
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Post Options Post Options   Quote sdm9465 Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 17:03
I don't think I would ever notice any possible loss of quality in a cRAW file but I still use RAW for all but action sports where I prefer the extra buffer room that cRAW allows. Why not use cRAW all the time? I convert all my RAW and cRAW files to .dng with lossless compression when I import them into Lightroom. The .dng files end up being around the same size as cRAW no matter whether they originate as RAW or cRAW. Since storage space is the same for me I figure there's no reason to take the chance (even though it is almost definitely a non-issue).
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Post Options Post Options   Quote Peekayoh Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 17:14
Originally posted by GrahamB GrahamB wrote:

Originally posted by Peekayoh Peekayoh wrote:


I have 32MB of CF cards which I found a bit limiting for my A700 plus, only 2x8MB cards are 300x (45MB/sec), the rest are old and slooow.
For my newly acquired A900 and contemplating a 10 day trip, I figured I needed another 2x32MB cards to be safe. Ouch! Nearly L400 and out of the question having just blown the budget (and a bit more) on the A900 + CZ16-35mm.

I have 3 16GB Transcend 400x cards, and just purchased a 32GB card for use in my a850. In the US, the 16GB sells for $60 and the 32 for $110. I checked Amazon UK link. The prices are a bit higher, but still 1/2 of your quote.
The Transcend 400x exceeds the a900's 5fps requirements and comes with a lifetime warranty. I've used Transcend almost exclusively since picking up 4GB 133x cards for my KM 7D. 8GB 266x worked well in my a700 and now 400x 16 and 32GB for the full frame. 5+ years, multiple cards and cameras and approaching 100,000 actuations without a single hiccup lets me recommend Transcend without reservation.
Graham

It's good to know of your success with Transend cards, but problems have been reported using the A900 with Trancend, A-Data, Kingmax and some Kingston cards (and maybe others); any cheap CF cards may be suspect.

In addition, there is nothing easier than for counterfeiters to stick a false label on cheap memory and make BIG profits, so be aware that cheap Sandisk Cards off the web are likely to be counterfeit and only buy from legitimate sources who give refunds.

I am very confident in using and recommending GENUINE Sandisk or Lexar Pro. I just looked at Warehouse Express and found SanDisk Extreme 32GB 400x UDMA Compact Flash selling for L190 (it may well be cheaper in the US). 300x memory would have sufficed but that seems to be unavailable now.

BTW, my decision was not totally based on price, I'm not completely happy at having all those images (825 RAW or 1254 cRAW) on a single card for 10 days or for however long it takes to get to a computer for backup. As it is, for L320 (when I get that second device), I'll have more fully backed up portable storage than I need in the short term, be future proofed for storage in the longer term (A9xx), have some wriggle room for Video if I ever go down that route and the life of my 2x 8GB cards will be extended.

I know this solution will not be to everyone's taste, but it is my colution and I thought I would share.
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Post Options Post Options   Quote groovyone Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 17:20
I get the feeling this discussion will never end without cold hard facts.

I shoot cRAW for everything. I may switch to RAW for an upcoming wedding.
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Post Options Post Options   Quote Fuzzphoto Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2010 at 18:46
No two images are the same, and as long as you need to make two separate exposures to show the difference between the two formats, you aren't proving anything. So, it's simply technically impossible to provide conclusive proof, unless you have access to the camera's firmware and are able to derive both file formats from the same exposure.

I'm convinced Sony provided both file formats in the first place to avoid uncompressed-RAW proponents switching to competing brands.
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