Compressed or uncompressed?

[zlatkob]

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So Leica M9 shooters have the choice between four options:

1. No compression at all — lossless — file size 34.8 MB.
   
2. Leica DNG compression only — lossy — file size 17.4 MB.
   
3. Adobe DNG compression only — lossless — varying file size, approx. 20 MB on average.
   
4. Leica and Adobe DNG compression both — lossy — varying file size, approx. 10 MB on average.
   

I'm curious whether you've settled on one of those four options for your photos. Which seems the best to you? I am doing #2 for the moment.

[Rolo]

01af,

anyone who will point out the difference between my "half" and 42.9% in a general conversation in a Forum like this is worth listening to , in my book.

 

I did say my explanation of the compression method was cartoon to help laymen understand. I'm not a physicist, or a colour scientist, I'm a photographer with some knowledge and keen to gain knowledge. Unfortunately, your explanation of what's going on takes us no further forward. You go square rooting and end up with the conclusion I made the losses are in the highlights.

 

What I'm keen for you to add to your analysis, is whether it makes any difference to us as practising photographers, either now, or in the future. In your opinion, have Leica, and every other camera manufacturer got us wasting our time standing around waiting for a camera to process uncompressed data that is no use to us now, or ever in the future ?

 

Are there any cases where the uncompressed data would be useful. As a photographer, I find that high dynamic range shots where the highlights are pushing the limits, can be more easily processed with subtle detail in the highlights when it's Uncompressed. You can tell me I'm wrong in this, I await your response and an easier workflow with enthusiasm.

 

For marketing reasons alone, I find it difficult to imagine that Leica could abandon Uncompressed DNG capture, on the basis that it is of no value to us. What's you precise take on this - a 100% waste of time to shoot anything other than Compressed, or only 42.9 % ?

 

You have to draw a conclusion to take this forward.

 

 

 

Quote

Actually, not. The lossy Leica DNG compression discards 3/7, or 42.9 %, of the data.

 

Actually, the gaps are fairly small, and they are particularly small in the shadows and wider in the highlights, in a way that matches our visual perception.

 

Your outline of the Leica compression method is wrong. There will be gaps but not as many as you're suggesting. It actually works along these lines: The original pixel data after A-to-D conversion are numbers between 0 and 16,383. These get multiplied by four and then the square root extracted and the results rounded to integer values. This rounding operation is where the data loss occurs. This yields integer numbers between 0 and 255 which get stored. The square root extraction is a non-linear operation which affects the high values more than the low.

[tele_player]

Good summary. However, I still have my doubts about "lossless" compression. When all is said and done, any compression loses data,

 

This is incorrect, as others have written - but I'll restate it. By definition, a 'lossless' compression algorithm is symmetrical, meaning that If you take file 'F1', compress it to make file 'F2', then decompress file 'F2' to make file 'F3', files F1 and F3 are bit-for-bit identical. All three files contain the exact same data - but F2 is encoded for more efficient storage.

 

The downsides of lossless compression are a)that the amount of file size reduction is less than if some data is discarded, the amount of file size reduction depends on the original data, and c) CPU time spent compressing and decompressing. There's no reason to suspect Adobe's lossless compression is, in fact, lossy - algorithms for doing lossless compression are very well known and have been in common use for, well, forever in computer terms.

[diogenis]

Photographers who are low-volume leisure shooters may have different needs and constraints than photographers who shoot more heavily and/or depend on photography for their income.

 

Indeed, maybe some "low-volume" leisure photographers may demand the highest they can get, but then so does some high-volume shooters.

As I said, no matter what you do, storage comes real cheap now. Financially it won't make a difference. There are even systems that can grow as you grow your library... easily, transparently and safely

[stunsworth]

01You go square rooting and end up with the conclusion I made the losses are in the highlights

 

One of the problems with a the way current sensors work is that for any given pixel half of the values it can record are in the brightest stop. It would have been better is the response was non-linear and that each stop was allocated the same range of values.

 

However, we are where we are, and it's possible - though I can't do (or be bothered to attempt to do) the maths - that Leica's compression routine (x4 followed by square root) allocates more values to the shadows in the darkest couple of stops that a traditional linear approach.

[Jeff S]

I'm at a loss here, feeling a bit depressed.

 

Jeff

[jaapv]

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I'm curious whether you've settled on one of those four options for your photos. Which seems the best to you? I am doing #2 for the moment.

Seeing that #2 and #3 give comparable reductions, I would personally choose the lossless option #3, seeing that the real losslessness has been argued convincingly #2 is losing data that matter right now imo, let alone in the future.

[Rolo]

101 Steve.

 

The response wanted is does Uncompressed make ANY difference, now or later. 01af will be back to define it for us and answer the original post.

 

 

 

One of the problems with a the way current sensors work is that for any given pixel half of the values it can record are in the brightest stop.

[01af]

I did say my explanation of the compression method was cartoon to help laymen understand.

But your explanation is full of errors an inaccuracies, so rather than helping to understand it actually is muddying the waters. After your "explanation", Leica's DNG compression looks much worse than it really is. Not very helpful.

 

 

What I'm keen for you to add to your analysis, is whether it makes any difference to us as practising photographers, either now, or in the future. [...] Are there any cases where the uncompressed data would be useful?

That's a good question. I don't know the answer.

 

However, my point is this: Do not confuse the question above with the question how the Leica DNG compression works in the first place. Let us get the latter straight. Only then we may turn to the former. To me, it seems you have an agenda when you're "explaining" the Leica compression—it looks as if you want to deliberately drag the uninformed reader to the conclusion it definitely did make a difference for practising photographers.

 

My agenda is to inform the uninformed so they can draw their own conclusions.

 

 

What's your precise take on this—a 100% waste of time to shoot anything other than Compressed, or only 42.9 %?

What makes you think I said shooting uncompressed was a waste of time?

 

 

You have to draw a conclusion to take this forward.

No I don't. At the moment, I am just trying to keep you from taking this backward.

[01af]

I'm at a loss here, feeling a bit depressed.

My sympathy ... still glad you're not feeling compressed.

[zlatkob]

As I said, no matter what you do, storage comes real cheap now. Financially it won't make a difference.

It may not make a difference to you, but I've explained several ways (money, time, space) in which it makes a difference to me.

[Rolo]

01af

 

Ok. Let me state categorically and clearly that I don't give a flying F' how the M9 compresses it's data. I have no agenda and no desire to mislead this or any other audience. You're welcome to the technology, I just want to use it to best advantage. Are you 100% clear on that. If I've muddied the waters for anyone, I apologise. If it wasn't helpful in part, I'm surprised.

 

Now the "good question", the only important question - does it make a difference ? Thank you for your direct answer on this - you don't know !

You want to maintain the accuracy of the process, but with all your knowledge of that - you don't know.

You tell me I'm wrong about half and 42.9%, accuse me of having an agenda, but - you don't know.

I can hardly believe it.

 

So, I say I've seen the difference when working in the larger files. Leica markets the difference. Logic says there must be a difference. Common sense says there must be a difference (one day maybe). I was truly expecting you to confirm it. OMG.

 

 

But your explanation is full of errors an inaccuracies, so rather than helping to understand it actually is muddying the waters. After your "explanation", Leica's DNG compression looks much worse than it really is. Not very helpful.

 

 

 

That's a good question. I don't know the answer.

 

However, my point is this: Do not confuse the question above with the question how the Leica DNG compression works in the first place. Let us get the latter straight. Only then we may turn to the former. To me, it seems you have an agenda when you're "explaining" the Leica compression—it looks as if you want to deliberately drag the uninformed reader to the conclusion it definitely did make a difference for practising photographers.

 

My agenda is to inform the uninformed so they can draw their own conclusions.

 

 

 

What makes you think I said shooting uncompressed was a waste of time?

 

 

 

No I don't. At the moment, I am just trying to keep you from taking this backward.

[Jeff S]

My sympathy ... still glad you're not feeling compressed.

 

You missed the subtlety of my italics on 'de' That's what happens when one compresses the font. (Assume you got the "at a loss" part)

 

Jeff

[sandymc]

Maybe they are both:

Both irrelevant and you can show them differences if you know where to look. Just as the case with mp3: with a high end system you are able to spot quality, but in the end it's irrelevant.

I can bet, Sandy knows where to look and spot them

 

No, really, the DNG lossless compression really is lossless. Same technology as Ziping a file.

 

Sandy

[01af]

Let me state categorically and clearly that I don't give a flying F' how the M9 compresses its data.

Yeah sure. From this post, that was glaringly obvious.

 

 

... but—you don't know. I can hardly believe it.

Your problem is, you can't tell one question from another. That's why you're so confused.

 

 

Now the "good question", the only important question—does it make a difference? [...] Logic says there must be a difference.

See? Again you're confusing two different questions.

 

The first question is this: Is there a difference between compressed and uncompressed Leica DNG files? The obvious, logical, and undisputable anser is: Yes, there is.

 

The second question is this: Does the difference between compressed and uncompressed Leica DNG files make a difference to the practising photographer? And the answer is: There is no easy answer. There are many answers. That's why the Leica M9 leaves the choice to the practising photographer. To some, the answer is: No. To others, the answer is: Yes, compressed is better. To still others, the answer is: Yes, uncompressed is better. To yet others, the answer is: Depends. To yet others still, the answer is: I don't know.

 

Now comes Rolo OMG can't believe it, and wants to know: Which of all these answers is the correct one?

[01af]

You missed the subtlety of my italics on 'de'

I didn't miss the italics but I'm afraid I didn't fully understand the meaning thereof. However now I think I got it. You're feeling like a bit that got thrown away in the process of lossy compression, right?

[diogenis]

It may not make a difference to you, but I've explained several ways (money, time, space) in which it makes a difference to me.

 

Time, maybe.

Money, how? Give me an example. What are you using to store your client's files at?

[Jeff S]

I didn't miss the italics but I'm afraid I didn't fully understand the meaning thereof. However now I think I got it. You're feeling like a bit that got thrown away in the process of lossy compression, right?

 

I more concerned with lousy compression than lossy compression...the difference is between u s.

 

Jeff

[Rolo]

To some, the answer is: No. To others, the answer is: Yes, compressed is better. To still others, the answer is: Yes, uncompressed is better. To yet others, the answer is: Depends. To yet others still, the answer is: I don't know.

 

EUREKA !!

 

:rolleyes:

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Hallo,

Look here: Leica M

[01af]

I more concerned with lousy compression than lossy compression ... the difference is between u s.

You are very creative. Your depression can't be so bad.