Nikon D800 processing images

[Steve Axford]

I had a look at what I could find on compression algorithms and it seems likely that all compression potentially changes the image slightly at the extremes. I imagine that a totally black (or white) field with only noise, would ideally be read as a totally black field plus mathematical noise. Then, when decompressed, the totally black field would have noise added, which would be mathematically correct, but in fact different. I understand that Fourier transforms and inverse transform are used (I dropped out of maths at about that point) and that could imply a level of uncertainty. The choice of where to put the line which says two things are the same is open to some discussion. (It's 1.99999999999, lets call it 2)

[swifty]

I think we may never know since Nikon doesn't document this aspect.
Not doubting your results, AK but are the two pictures identical to begin with?
The reason I ask is that it is actually generally very difficult to shoot two identical images. Even such things as aperture not stopping down to exactly your specified aperture affects things or small fluctuations in light, especially natural light.
But the fact you had a few sets and your results can be repeatable with each set would lend credibility.
Either way, I think the take home might be the differences, if present are too small to worry about and at least satisfy a representation of 'visually lossless'.
As to post processing speed, if anyone is interested you would probably need to run a batch process of 100 or something in larger quantities before possibly seeing differences. Which again, even if there are differences it would be too small to care about for most of us.

[arthurking83]

.... Which again, even if there are differences it would be too small to care about for most of us.

This is the key point.

The images aren't 100% identical, but close at 99.999%.
Even tho the exposures were identical, the actual images were slightly different to begin with, and the weird part is that the uncompressed version was actually slightly brighter(more blown out) than the lossless image.
Now when I say slightly brighter, they appear to be identical(to my eye), but the histogram shows slightly brighter tonal numbers overall, then the lossless version.

The reason I made the initial comment to begin with is that even tho the uncompressed image is the brighter of the two(with blown highlights), in the -2Ev recovery it was the image that (only just) displayed slightly better highlight detail
Common sense would dictate that the darker of the two comparative images would recover better.

Problem is when converted to jpg, the differences aren't there.. it's only in the raw file, viewed as a raw file in VNX2.
(ie. VNX2 can be set to view either the (faster to load) jpg preview file, or the (slower to load) actual raw file data .. which it has to decode to view(obviously).
ps. I haven't tried tiff file conversion to see if the very slight differences are still obvious.

But, like I said earlier too .. you can't really see any differences when casually flicking between the two different images, it's only the subtle change in histogram that diverts your eye, and then you go 'looking harder'.
Then I hover the mouse over an area that is not blown out in the uncompressed image, and the RGB values are listed for those pixel areas ... say: 248, 244, 250, just as a random example for the uncompressed image. And the lossless image at those same pixel coordinates read RGB values of 255, 255, 255 by way of comparison.
If I use the H key to display blown highlights, there are less on the uncompressed images than there are on the lossless images.

As per your comment above .. I think it applies for almost all of us in the real world .. that is a variation of (say) 1/12 Ev in an image isn't going to make or break the image.


In a few days, I should have the time to check the issue out with a more controlled test. (It'll give me something to do if I can't find anything else).

[Steve Axford]

Arthur, you seem to assume that VMX2 is the best software to use, yet you also assume that almost no reviewer would use it. If almost nobody uses it, why base test results on it.

[arthurking83]

1/. Arthur, you seem to assume that VMX2 is the best software to use,

2/. yet you also assume that almost no reviewer would use it.

3/. If almost nobody uses it, why base test results on it.

1/. never said that. But why use any software? why would you prefer to use what you do? Am I not allowed my own preference.
(btw: there are technical reasons why I use it too, but unrelated to the above issue)

2/. I've never read any review based on any Nikon camera, where the reviewer has mentioned the use of VNX2.
Many folks out there in Nikon land despise VNX2 for it's limited ability(agreed, it is limited in it's tools), and instability(never seen that in many years of using it)
My assumption is based on the above reasons.

3/. Why not? I guess it begs the question, why use any software to base tests of any raw conversion? Is one software particularly greater than any other? if so, is that not a 'preferential' based choice anyhow?(ie. refer back to 1/.)

[Steve Axford]

I agree. You can use any software you like for your processing. But, for a test like this it would make sense to use software that people actually use. You claim to find a difference in the results, yet nobody else does. That alone should start the alarm bells ringing. Perhaps you have discovered a major fault in the Nikon lossless compression. One that nobody else has found and one that would create quite a stir as it implies that Nikon have been less than honest in their claims. But perhaps you have made a mistake. That option would be worth checking before you suggest that there is a real difference between lossless and uncompressed. I know that there is a difference between Sony compression and uncompressed. But they don't claim to use lossless compression. The difference is quite small, but enough to cause some major criticism and force Sony to include uncompressed. If DPreview were to get a sniff that Nikon lossless compression wasn't really lossless, they would be crowing so loudly that you would be deafened.