M8 == 8bits

[hub]

Originally Posted by Richard Marks

It would be a pleasure
Im also quite happy to send you some files

Not files. The camera. As Dave was saying, it is hard to find a camera to try out because nobody around seems to have one, nobody rents one, and there is no way I'd shell out 5 Large + a lens just to try it.

If you argue that I haven't tried it, don't just offer to provide files. That's not trying out a camera.

[hub]

Originally Posted by xihalife

I've seen an article which describes a use of a look up table to compress 14-bit values. The trouble is that the look up table is indexed using 8-bit values, which means there are 256 pieces of 14-bit values. This is still not enough to capture a wide dynamic range, it's only enough to describe those 256 values more accurately. And no, the M8 does not behave like other cameras which save 12 or 14 bit data... that is a known fact. The lost highlights are one proof of that - M8 is the only high end camera I have seen which seems to clamp all color values to 1.0.

1. the number of bits does not preclude the dynamic range in any way. It is just an indication of the precision of the information. The more bits you have the more precision you get, ie real difference between to value very close, that might be rounded up. See it has the number of decimal digits (round to the nearset cent vs rounding to the nearest 5 cents). Also this include the noise, which the downside.

2. if you readuce 14-bits value to 8-bits like it is done, you LOSE infromation. in the end you have lost that precision and you can't recover it. Note that for those who say "it is because they don't have enough power" I'd reply that they actually require more processing to perform this operation.

And FYI, some lower end Nikon do that, but the quantization table provide an everage of 9.4bits of information.
See http://www.majid.info/mylos/weblog/2004/05/02-1.html

That lead to another question: is the JPEG file generate on camera by these 8bits RAW data samples or is it done from the upstream data? But who can answer as the source code of the fimrware is not available, nor any documentation.

[ferider]

Originally Posted by hub

1. the number of bits does not preclude the dynamic range in any way. It is just an indication of the precision of the information.

Formally speaking that is wrong. The number of bits does define the dynamic range for digital signal processing.

Much like dB in the analog context.

----------
Added: I guess I should elaborate - sorry for the geek talk:

Assume you have a black-box processing an input signal and generating an output signal. The "Dynamic Range" of the box is defined by ratio of largest signal divided by smallest signal that you can transmit. Which means, if you add, on input, a small signal to a large signal you should still see a different output than if you just transmit the large signal. For a digital box, the smallest signal is 1 bit. The largest 111111... (repeat nr. of bits you can transmit). The dynamic range is proportional to log(11111...../1), i.e. proportional to the nr. of bits.

It's a well defined term in engineering.

[Richard Marks]

Originally Posted by xihalife

I use the M8 a lot so I don't really know why mr. Marks keeps saying I am not qualified to state an opinion until I've tried it. The mentioned HDR trick does nothing to salvage lost highlights and it does nothing to improve color that is lost in dark areas. It only works if the shot is ok to begin with, which is to say that the colors lie in the range that the 8-bit file can store them.

.

Forgive me! You can and of course express any opinion you like and this is much appreciated. It is simply that it is a bit more believable if it is qualified by factual experience.

I think we shall have to agree to differ.

A most informative thread for all concerened.

Best wishes

Richard

[sandymc]

Without wanting to spoil the fun, the 8-bit to 14-bit comparason's been done, at least in synthetic form:

http://www.l-camera-forum.com/leica-...-bit-dngs.html



Sandy

[sandymc]

Originally Posted by ferider

Formally speaking that is wrong. The number of bits does define the dynamic range for digital signal processing.

Much like dB in the analog context.

----------
Added: I guess I should elaborate - sorry for the geek talk:

Assume you have a black-box processing an input signal and generating an output signal. The "Dynamic Range" of the box is defined by ratio of largest signal divided by smallest signal that you can transmit. Which means, if you add, on input, a small signal to a large signal you should still see a different output than if you just transmit the large signal. For a digital box, the smallest signal is 1 bit. The largest 111111... (repeat nr. of bits you can transmit). The dynamic range is proportional to log(11111...../1), i.e. proportional to the nr. of bits.

It's a well defined term in engineering.

Sorry, not so. Number of bits defines dynamic range only for systems using linear encoding. Which the M8 definitely is not.

Sandy

[Paul Kay]

I guess that the bottom line problem is actually determining how all this theory actually translates into practice. On the one hand you have people like myself, and clearly others too,who have a practical view and have actually tried the M8 (and other cameras) and have come to the conclusion that the M8's 8-bit files are perfectly adequate if utilised to shoot subject matter in ways that suits both us and the camera. On the other hand there are theorisers and users to whom the issue is a significant drawback and who either believe that they need the highest bit depth possible or find aspects of their shooting style and subject matter is not suited to Leica's 8-bit output.

Not sure where the discussion can go to from here if I'm totally honest!

[ferider]

Originally Posted by sandymc

Sorry, not so. Number of bits defines dynamic range only for systems using linear encoding. Which the M8 definitely is not.
Sandy

Not sure what you mean by linear. Linear in terms of Gallois field function ?

Do you know if or not the M8 uses a non-linear code ? I doubt it.

In any case, the encoding does not matter. It's the information quantity that matters. Measured in bits. Go the other way and you will see. Take an 8 bit signal, and encode into, say 12 bits. You still have 8bit dynamic range.

[jaapv]

Originally Posted by hub

Not files. The camera. As Dave was saying, it is hard to find a camera to try out because nobody around seems to have one, nobody rents one, and there is no way I'd shell out 5 Large + a lens just to try it.

If you argue that I haven't tried it, don't just offer to provide files. That's not trying out a camera.

Hmmm. Your posts read that you are having problems with the files you can expect. I would say it was a fair offer.

[JohnL]

Originally Posted by ferider

Not sure what you mean by linear. Linear in terms of Gallois field function ?

Do you know if or not the M8 uses a non-linear code ? I doubt it.

In any case, the encoding does not matter. It's the information quantity that matters. Measured in bits. Go the other way and you will see. Take an 8 bit signal, and encode into, say 12 bits. You still have 8bit dynamic range.

Bit depth and dynamic range have no direct relationship. Dynamic range is the number of stops (or other measure of difference in light intensity) from black (zero) to the brightest value in each channel that just doesn't blow the highlights. This is a function of the sensor technology. Bit depth determines the number of steps into which that range is divided, i.e. the precision with which each different level is measured and recorded. According to Leica, they measure at 16 bits, but only record 8 (both per-channel, of course). They claim to have done some magic with the use of those 256 levels (per channel), which definitely suggests non-linearity, so as to enhance the shadows (or was it the highlights?). However, with only 256 levels per channel, I strongly suspect the raw (DNG) files will not be terribly robust under more than minimal manipulation. This is one of the two primary reasons why I decided not to buy an M8. The other was the crop sensor, and the consequent non-stellar high ISO performance.

Edit: fixed typo.

[ferider]

Sorry John, you are wrong: its the number of stops from the darkest grey (not black) to the brightest grey (not white), divided by the smallest amount of grey (1bit) that you can add to ANY GIVEN shade to make it change tone to the eye.

Reducing bits increases entropy and descreases dynamic range, in other words gets noise level closer to signal level. It's a basic law of information theory.

Further, a linear code does not imply a linear function from grey to grey or color to color. These are two different things.

Dynamic range is not a measure of smallest vs. largest signal a camera can receive and process. It is a measure of a cameras ability to receive small signals while in the presence of large ones, across the entire signal spectrum.

Roland.

[Richard Marks]

Originally Posted by hub

Not files. The camera. As Dave was saying, it is hard to find a camera to try out because nobody around seems to have one, nobody rents one, and there is no way I'd shell out 5 Large + a lens just to try it.

If you argue that I haven't tried it, don't just offer to provide files. That's not trying out a camera.

My reply said "it would be a pleasure" to lend you my camera. Clearly you would have to visit the UK but the offer is there! The next best thing i could do is send you some files. More than that i can not do! But you simply can not make inferences about how images might appear based on specification of electronic components. Surely your local leica dealer can lend you a camera for an afternoons trial. If this is also impossible then there seems very little point in you debating about this camera as you can not trial one and dont wish to buy one. Be happy with what you have!

Regards


Richard

[sandymc]

Originally Posted by ferider

Not sure what you mean by linear. Linear in terms of Gallois field function ?

Do you know if or not the M8 uses a non-linear code ? I doubt it.

In any case, the encoding does not matter. It's the information quantity that matters. Measured in bits. Go the other way and you will see. Take an 8 bit signal, and encode into, say 12 bits. You still have 8bit dynamic range.

The M8 uses a square law function: y=(x*4)^0.5

Re encoding and dynamic range: Take a look at the first line of this: http://en.wikipedia.org/wiki/A-law_algorithm

Sandy

[Paul Kay]

Originally Posted by ferider

It's the information quantity that matters.

I wasn't going to repost here but....

I'd have to disagree! Its actually the USEFUL, USABLE information which matters. Most digital cameras are apparently rich in highlight information (no I'm not talking about over-exposed files) much of which is irrelevant to the final output image - discarding some of this (as I believe the M8 does) is very unlikely to result in VISIBLE tonal differences in a final print or upon projection.

Sure they will be instances where someone does need this data but on balance I'd suggest that this is rare. Most of the issues I have had with digital files from any camera are to do with high saturation levels and shadows, neither of which is, I suspect, adversely affected by reduced highlight data. Remember we are discussing pictures here, not technical studies for scientific use which are probably not the M8's forte!

[Richard Marks]

Originally Posted by Paul Kay

I wasn't going to repost here but....

I'd have to disagree! Its actually the USEFUL, USABLE information which matters. Most digital cameras are apparently rich in highlight information (no I'm not talking about over-exposed files) much of which is irrelevant to the final output image - discarding some of this (as I believe the M8 does) is very unlikely to result in VISIBLE tonal differences in a final print or upon projection.

Sure they will be instances where someone does need this data but on balance I'd suggest that this is rare. Most of the issues I have had with digital files from any camera are to do with high saturation levels and shadows, neither of which is, I suspect, adversely affected by reduced highlight data. Remember we are discussing pictures here, not technical studies for scientific use which are probably not the M8's forte!

Paul I very much agree with this. Those who are imersed in theory might consider the analogy with lens design. All the myriads of graphs do not convey how an image looks from any given lens. There is simply no way one would purchase a lens based on MTF tables.
Richard

[yclinn]

However, this thread really pulled me back from buying an M8 at present.

[jaapv]

Originally Posted by yclinn

However, this thread really pulled me back from buying an M8 at present.

Why? Wouldn't it be better to make your own judgment instead of obeying anonymous voices on the Internet? And if you like cyberinput in your decision making, did you actually look at images taken by the camera instead of theoretical discussions, which have but limited application to the actual photographic process?
I had a look at your rather nice gallery; there is not one photograph there that would be affected by the considerations raised in this thread.

[Paul Kay]

Originally Posted by yclinn

However, this thread really pulled me back from buying an M8 at present.

Hello yclinn

Looks to me like you are a film user.

Do you read up on the technical specification of a film before using it, checking things like its colour accuracy, number of layers, anti-halation measures, granularity, etc.? I very much doubt it. You probably do what the vast majority of people do - look at the results. Nothing has changed. You can still assess image quality visually - this still remains the ultimate test!

I supply image files to my clients - they often have no idea what camera I've used. I've shot on the M8 and had the files used for publication with no queries whatsoever. I'm just not sure where this discussion can go - really the only solution to doubts over the M8's 8-bit output is to try the camera and appreciate its files for yourself - and yes there will be subject matter it doesn't handle well, but this is equally true of ALL digital cameras.

[dcsang]

heh...Paul (and others) .. you guys are neglecting the fact that it doesn't cost $5000 to go out and try different 3-4 different rolls of film

As I've said earlier; if the camera is available to rent - then I'd be willing to do so just to see for myself - but it's not. For the cost of a "rental" to me; about $1,000 minimum, I can buy about 100 rolls of film to try for myself to look at the results

Cheers,
Dave

[Richard Marks]

Originally Posted by dcsang

heh...Paul (and others) .. you guys are neglecting the fact that it doesn't cost $5000 to go out and try different 3-4 different rolls of film

As I've said earlier; if the camera is available to rent - then I'd be willing to do so just to see for myself - but it's not. For the cost of a "rental" to me; about $1,000 minimum, I can buy about 100 rolls of film to try for myself to look at the results

Cheers,
Dave

Dave I am puzzled by this. You are a serious professional photographer and certainly in the Uk any of the leica dealers would be delighted to arrange a free days demo. If you are already a Leica owner it is free. Is this not so where you are? Have you tried? You simply have to do this as you are a frequent and valued opinion on the M8 section of RF. Have you seen Good Will Hunting? There is a wonderful bit where the brilliant (but deranged) mathematician is quoting all sorts of data about the Cystain Chappel but his psychiatrist (Robin Williams) asks him "What does it smell like in there?" and he realises that actually he has never been there! Needless to say I would be glad to oblige but a trip to the UK would seem a little unnecessary.

Richard

[Richard Marks]

Originally Posted by yclinn

However, this thread really pulled me back from buying an M8 at present.

Great
Looks like we have saved you quite a lot of money. All part of the service.

Richard

[jaapv]

Am I happy that I don't use specs to make a photograph but a real live camera...

[yclinn]

I would go for a Nikon D3 definitely if I had not sold out all the Nikkors when I bought my first leica (Minilux) several years ago, M8 is merely a way of digitize my photos which are used to record events of my families and activities, a 1.33x crop is not a weak-point for me, it provides different framing choice on a certain lens when used on an M8 compared to that on an M6.
To the 8-bit issue, I just wonder if Leica is gonna provide a firmware upgrade.

[dcsang]

Originally Posted by Richard Marks

Dave I am puzzled by this. You are a serious professional photographer and certainly in the Uk any of the leica dealers would be delighted to arrange a free days demo. If you are already a Leica owner it is free. Is this not so where you are? Have you tried? You simply have to do this as you are a frequent and valued opinion on the M8 section of RF. Have you seen Good Will Hunting? There is a wonderful bit where the brilliant (but deranged) mathematician is quoting all sorts of data about the Cystain Chappel but his psychiatrist (Robin Williams) asks him "What does it smell like in there?" and he realises that actually he has never been there! Needless to say I would be glad to oblige but a trip to the UK would seem a little unnecessary.

Richard

Richard...

There are, as I sit here, maybe, a whopping four places that I can go to purchase a Leica M camera within Toronto. I can count that on one hand.

Out of those four I would have to order the camera in from, at least, three of them.

Retailers do not order in just so someone can "try" or "demo" the camera for a day or two.

The retailers are: Vistek, Harry's Pro Shop, Eight Elm Camera and, maybe, Henry's.

I'm not sure about Henry's.
I'm sure about Vistek - and based on their customer service and the decline of their retail stock - I do not think they would lend it out - if they don't have it for rental, they ain't handing it out either
Harry's Pro Shop is a grey market dealer but a good guy and, in general, very reasonable pricing - but I know for a fact that if I ask, I'm ordering - I'm not trying out a piece he has in stock - because he doesn't carry stock.
Similarly, Eight Elm Camera has to order the camera - heck they're supposed to also carry Voigtlander but they don't even have Voigtlander cameras in stock - you have to order them.

So.. ya.. "going in and trying" ain't gonna happen

That said; a small group of wedding photographers in the area may get together and I know there will be a couple M8's there for sure - at that point, I may get to try it briefly.

And speaking of wedding photographers; I wish I could repeat what's been said on the Digital Wedding Forum I belong to, but after reading a post from a well respected UK wedding photographer who used his film Leica M's for a long long time before switching to Canon digital, I'm completely turned off even considering the M8 for wedding work. It did, however, get good reviews as a hobbyist cam - and that is fine - but if I'm spending $5450 (after tax); I'd like to be able to write some of that down ya know?

Cheers
Dave

[Richard Marks]

Originally Posted by dcsang

Richard...

There are, as I sit here, maybe, a whopping four places that I can go to purchase a Leica M camera within Toronto. I can count that on one hand.

Out of those four I would have to order the camera in from, at least, three of them.

Retailers do not order in just so someone can "try" or "demo" the camera for a day or two.

The retailers are: Vistek, Harry's Pro Shop, Eight Elm Camera and, maybe, Henry's.

I'm not sure about Henry's.
I'm sure about Vistek - and based on their customer service and the decline of their retail stock - I do not think they would lend it out - if they don't have it for rental, they ain't handing it out either
Harry's Pro Shop is a grey market dealer but a good guy and, in general, very reasonable pricing - but I know for a fact that if I ask, I'm ordering - I'm not trying out a piece he has in stock - because he doesn't carry stock.
Similarly, Eight Elm Camera has to order the camera - heck they're supposed to also carry Voigtlander but they don't even have Voigtlander cameras in stock - you have to order them.

So.. ya.. "going in and trying" ain't gonna happen

That said; a small group of wedding photographers in the area may get together and I know there will be a couple M8's there for sure - at that point, I may get to try it briefly.

And speaking of wedding photographers; I wish I could repeat what's been said on the Digital Wedding Forum I belong to, but after reading a post from a well respected UK wedding photographer who used his film Leica M's for a long long time before switching to Canon digital, I'm completely turned off even considering the M8 for wedding work. It did, however, get good reviews as a hobbyist cam - and that is fine - but if I'm spending $5450 (after tax); I'd like to be able to write some of that down ya know?

Cheers
Dave

Dave

This is unbelievable! UK Leica dealers have demo cameras because Leica realised that they would have a tough job selling any without a trial given the very real alternatives for a lot less cash (ya know). It sounds like Torronto could do with a new Leica dealer! I really wish I could help just because this camera is worth a try (ya know)

I am familiar with digital wedding forum and I think I know the UK guy that you are referring to. If I am correct he says an M8 can not be your only wedding camera. Certainly my reservation of the M8 for weddings is the TTL flash / flash options with an M8 are lousy. The other issue is things get super expensive if you need to allow for 2 bodies. Reportage style of weddings are very popular in the UK and I would have no reservations using an M8 for those.

A bit ago I covered a new church openning and the Bishop of Derby specifically complimented me on how nice it was not haveing a dirty great camera and flash ruining the proceedings!

8 bit image! (sorry)
Rothwell Church-0038.jpg

Regards

Richard