In camera processing RAW v JPG comparison

[robski]

Originally Posted by Stephen Fox

I am considering using uncompressed RAW from now on

Puzzled ??? Are you saying Nikon are using a lossy compression method with their RAW format ! This does not make sense.

The only reason not to compress when using a lossless method is normally is to save the processing overhead of compressing and decompession.

[Don Hoey]

Very impressive results Stephen.

I noticed the difference on the rim of the can at 1:1 magnification. The label was there at 150%.

This to me clearly shows how digital image processing has improved over the years.

The other thought when seeing this is to compare it with good old film and wonder at the ISO equivalent. I think the thread ' Thoughts on DSLR's future developments ' has some relevance as would you want more resolution than this appears to show. It may be interesting for you to do a similar pic of everyday objects and post it in that thread.

Doing so could of course generate personal expense for me.

Don

[Canis Vulpes]

Originally Posted by robski

Puzzled ??? Are you saying Nikon are using a lossy compression method with their RAW format ! This does not make sense.

The only reason not to compress when using a lossless method is normally is to save the processing overhead of compressing and decompession.

We shall see...

I should have posted four images taken over two shots, two RAW and two JPEG's.

I intend to do test version three using the same can of tomato's tomorrow evening or over the weekend.

[pip22]

I see it this way -- you can shoot raw and convert them all to tiff or jpeg, but you can't shoot jpegs and convert them to raw, it's too late. I've decided to put up with the extra work involved working with raw files for that very reason. Once you allow your camera to process the raw data instead, you've much less room to maneouvre at the editing stage.

[Don Hoey]

Originally Posted by robski

Puzzled ??? Are you saying Nikon are using a lossy compression method with their RAW format ! This does not make sense.

The only reason not to compress when using a lossless method is normally is to save the processing overhead of compressing and decompession.

Rob,

Your question really got me thinking and as a result I have spent a good slice of today trying to find an answer.

The only info on the subject I can get is from Thom Hogan reviews. From these the D100 RAW is not compressed but the D70, and D50 are. As you are the tech. type I will link both of his reviews. The info is half way down the page. In his review of the D2X there is no mention of Compressed RAW but it would seem logical that it is the same as the D50 & D70.

We now need a couple of tests from Stephen when he has some time.

Thom Hogan D50 review http://www.bythom.com/D50REVIEW.htm
Thom Hogan D70 review http://www.bythom.com/D70REVIEW.HTM

Don

[Canis Vulpes]

I'll do a couple of tests but I have a busy weekend ahead so might not be for a few days.

Here is what Nikon have to say in the tail end of a piece regarding JPEG v's RAW and compressed RAW. Read all they way through as it add more weight and information regarding compressed NEF toward the end.

Compressed NEF
Compressed RAW format available in Nikon cameras (and which can be processed by Nikon Capture) employs a strategy that uses the subjective nature of human perception to reduce the overall data volume while maintaining its quality.

Compressed RAW format algorithm claims to be visually lossless because it treats data differently according to the areas there effects of reduction are masked. It therefore applies compression only to areas which will not be critically visible in the final RGB result. In this respect it resembles part of the compression concept of the widely accepted MPEG layer 3 (MP3). Using Compressed NEF, the data to which the process is applied has reduced significance to the naked eye – Whereas JPEG compression, on the otherhand reduces data based on the orientation and degree of detail, and therefore produces effects that are immediately clear.

The NEF compression strategy is based on the fact that the human visual system has differing sensitivity to tonal variations depending on whether they are highlight, mid-tone or shadow.

Compression is applied selectively so that the effect is minimised and in most cases undetectable to the human eye at normal viewing distances.

In extreme cases the effect of compression may become visible, particularly in areas of an image where there is a combination of high levels of detail and brightness, or extreme saturation.

As the compression process is a mathematical operation carried out on subjectively accessed data, it is impossible to predict with accuracy the few types of image that might produce unfavourable results.

Nevertheless the compressed NEF format will offer the benefit of reduce data size with minimal sacrifice of quality compared with JPEG, and allow maximum flexibility to be maintained.

As a useful tip, it may be helpful to note that, as it is only areas of high saturation or brightness that may be affected, shooting one stop under will reduce the amount of data in the sensitive areas.

The decision on when and where to use the compressed NEF format is therefore dependent upon the experience of the user.

So far, Nikon’s tests* have failed to reveal any clear trend in subject type that maybe affected by the NEF compression. In fact it has been impossible in practical use to identify any artefacts when using the compressed format.

The main identifiable disadvantage is in the longer processing time required to create and decode a compressed NEF image, compared to an uncompressed NEF. However in cases where storage space or transmission bandwidth is at a premium compressed Raw remains a valuable option in the armory of today’s versatile photographer.

Reference
'NEF: No loss of data', Nikon Pro, April 2005, Cedar Communications.

It seem uncompressed is only to be used when blown highlights are to be expected in Y or any R, G and B channels.

[Don Hoey]

That was a very thorough explanation Stephen. Thank you.

A bit more detailed than in the two reviews.

From my looking around today it does suggest that uncompressed is used to wring every last ounce out of the sensor but with obvious consequences on file size. Not something that the average user is likley to require.

In film terms I can see it a bit like using Technical Pan at 12 ISO with a more complex development process, when a standard 25/50 ISO would surfice.

Don

[Gidders]

Originally Posted by Stephen Fox

WOW my back hurts after falling off my chair! ....

.....BANG - legs in the air and sore lumber region!

Are you sure its not more to do with the Abbots ale!

[Canis Vulpes]

Originally Posted by Gidders

Are you sure its not more to do with the Abbots ale!

LOL, I was waiting for that....

....and a sore head in the morning!

[Christine]

I would love to have a try with RAW but need a simple prog for conversion.I tried the Rawshooter essential from Pixmantec,but was told to paste a long website into a browser bar,so fell at the first hurdle,so to speak.Is there an easy download prog I could try?.