Film vs Digital - Dynamic Range

[rishij]

Bernie:<i>"Rishi... last time I saw HTP beaten to death on a forum (LL), it was agreed that HTP was nothing more than underexposure by 1 stop, then boosting the shadow data. You can implement it manually by dialling in -1 EC and then applying a bit of "fill light" in LR/ACR."</i>

<p>

Sweet. That was my first inclination when I read about HTP. Because they said it only works at ISO 200 or above. Which made me think "Hmm... that probably means that if you set it at ISO 200, it actually sets the sensitivity to ISO 100 then applies a non-linear gain".

<p>

But if each row of pixels (or is it columns? I forget) has its own amplifier, perhaps some non-linear gain can be done to the amplification on a row-by-row basis by somewhere implementing in the circuitry a way to determine gain based on total voltage across the row? I don't even know if that'd be worth it because it might help landscape photogs but certainly wouldn't help trying to photograph a bride's white dress (random highlights) filling up a frame with shadows everywhere else.

<p>

Bernie:<i>"I seem to remember it stated somewhere that as more silver ions are converted to silver metal at sensitivity centres, the less sensitive those centres become."</i>

<p>

Yup, good call. It's in Baines, "The Science of Photography". I think that's part of the reason behind why a clump at sensitivity speck post-exposure but pre-development can only get so big... additionally, they can't get too big because it's energetically very unfavorable to disrupt the crystal lattice. Another reason why clumps don't usually form in the center of grains but rather on the surfaces where imperfections already exist.

<p>

Vijay:<i>"OK Rishi - your tone was quite, umm shall we say - hostile."</i>

<p>

Yeah, ok, with all my 'thanks' and 'that'd be appreciated', clearly, so easy to see how I was being 'hostile'. You, on the other hand, with your: <i>"You don't know what you are talking about at all, do you?"</i>... that, yeah now that's what we call hospitable, huh?

<p>

If you're talking about the part where I was asking you to explain observations when your own comments/theory go against observation, I stand firm on that. In other words, instead of being so negative & shooting everyone down (which, sure, is necessary from time to time), offer a theory to EXPLAIN the observation then after you've knocked down a previous attempt to explain the observation. I still don't see ONE explanation from your end that explains the exposure latitude of negative film. Or the lack thereof of slide film. I understand shooting down theories (bad ones anyway) is part & parcel of good science, but, damn dude, try being on the other side for once. Contribute a theory.

<p>

Rishi

[vijay_nebhrajani]

<i>Bernie: "I seem to remember it stated somewhere that as more silver ions are converted to silver metal at sensitivity centres, the less sensitive those centres become. When I get home I'll try and find out if this is a correct recollection. Cheers."</i>

<p>

Sure that is a correct recollection. That has to happen, no doubt, otherwise film would have an infinite dynamic range. The point I'm making is that this is linear. Meaning that if you go from 10 ions to 20 ions, the effect is the same as if you were going from 100 ions to 200 ions (a decrease of sensitivity of 2x in either case). Nonlinearity is different - it implies that going from 10 ions to 20 ions will have a larger effect than going from 100 to 200.

<p>

If the latter were true, you wouldn't have the S-shaped sensitometric curve.

[rishij]

Vijay:<i>"The already formed latent image can't significantly affect further formation of the latent image because that would make the response non-linear, which it is not."</i>

<p>

Maybe after a certain density is reached, it can. Which would explain why the shoulder exists at higher log E. Maybe the clump of silver metal atoms has to be >20 (arbitrary) to start blocking visible light in any meaningful way to layers beneath. Just throwing it out there. Contributing an idea, y'know?

<p>

Vijay:<i>"Latitude is not a characteristic of a system; it is just what happens when a signal (light) has less dynamic range than the channel (film in this case). Talking about latitude as if it were a system characteristic (i.e., a property of film) is an exercise in meaninglessness."</i>

<p>

I think you mean "when a signal (light) has <i>more</i> dynamic range than the channel (film in this case)."

<p>

Furthermore, here we go with semantics again. Yes I understand that latitude in the sense of relation between the medium and what it's trying to record is what's important. What is the meaning of your comment? Latitude is still relevant to this discussion because apparently the latitude for the 40D is lower than that of Ektar 100 (or, less negative). Jeez man.

<p>

Finally, why are you speaking of the 'toe' and 'Dmin' for Ektar? We're interested in the 'shoulder' and 'Dmax', none of which even exist on the Ektar data sheet, but do exist in typical H&D curves. I guess Kodak just didn't go that far out. What we should be looking at is the log E range over which the 'shoulder' displays non-linear behavior. That, tied in with the linear region, would by its very definition simulate a variable gain amp. Certainly not an ideal one, but perhaps a crude one that would explain the exposure latitude that we see for negative film.

<p>

Rishi

[mauro_franic]

Vijay, "You miss the point that if the negative gets (say) 1.5 times as dense going from f/2.8 to f/2, it also gets 1.5 times as dense going from f/11 to f/8. "

 

No no no.... I know you must understand it but it's just late.

 

Please go to the link I sent you, pull a few points from the graph, and plot them in Excel on a linear axis. Then please, let me know what you conclude.

[rishij]

Vijay:<i>"as if you were going from 100 ions to 200 ions (a decrease of sensitivity of 2x in either case)"</i>

<p>

What are you talking about??

[mauro_franic]

Going to bed now...

 

Vijay, I thank you and enjoy the debate, I hope I don't sound offensive.

[vijay_nebhrajani]

<i>Rishi: "You don't know what you are talking about at all, do you?"... that, yeah now that's what we call hospitable, huh? </i>

<p>

Sorry. I got a little worked up. It's not like this is the first time I've faced hostility for what I said. Nevertheless, unconditional apologies.

<p>

About theories - well, do you observe a significant extension of dynamic range with software processing of film? Nope - maybe a full stop more. How is this observation in conflict to what I'm saying? OK - maybe you could extract a stop rather than the half stop I said. The point was that compared to the 13 stop linear range, this is not that significant.

<p>

Contribute a theory? Last I remember, I explained the whole process end to end - with gray grains and all; something that covered all observations - with support from information theory and whatnot. Please. Anyway, lets go to the other thread if you want to hash this out.

<p>

As for this thread, I've already defined exposure latitude in precise terms, and I'll gladly explain what I know. Sometimes I may refrain from an immediate explanation because it may not be necessary for the discussion at hand. If you assume based on that that I'm ignorant, so be it. If I don't know something, I'll tell you I'm speculating, or I'm guessing. So what do you want to know?

<p>

Why slide film has lesser dynamic range? I don't know. I speculate or I guess it has something to do with the reversal process. I wonder what happens when you cross process E-6 in C-41 chemistry - maybe the resulting negative has more dynamic range?

[bernardwest]

<i>The point I'm making is that this is linear. Meaning that if you go from 10 ions to 20 ions, the effect is the same as if you were going from 100 ions to 200 ions (a decrease of sensitivity of 2x in either case).</i><p>

 

But do we actually know this?<p>

 

Even if we assume this is true, the grain with 200 atoms (I assume you mean atoms, not ions) will be far less sensitive than the grain with 20 atoms. Let's do a simple (arggh, I hate to say it...) thought experiment and say that after time <i>t</i> one grain has 200 atoms and the other has 20 atoms. So after time 2<i>t</i>, lets say the more exposed grain has 250 atoms, and the other one has 35 atoms. ie. the more exposed grain reduces a lower ratio of silver atoms than the less exposed grain. Now we develop. Remember, development will begin sooner in the grain that has more silver at the sensitivity speck. But how much sooner comparetively would this occur, than say we developed after time <i>t</i>? I am speculating here, but lets assume that development initiation is directly linearly related to number of silver at a sensitivity site. So in the case of the less exposed grain, after exposure time 2<i>t</i> its development would begin in nearly half the time that it would after exposure time of <i>t</i>. But in the case of the more exposed grain, after exposure time 2<i>t</i>, its development time would begin in only 80% (or something like that if I could be bothered to work it out) of the time it would in after exposure time of <i>t</i>. So: double exposure time, doesn't lead to an across the board (tonal range) doubling of print tone.<p>

 

Did any of that make sense?

[vijay_nebhrajani]

<i>Rishi: "Maybe after a certain density is reached, it can. Which would explain why the shoulder exists at

higher log E. Maybe the clump of silver metal atoms has to be >20 (arbitrary) to start blocking visible light in

any meaningful way to layers beneath. Just throwing it out there. Contributing an idea, y'know? "</i>

<p>

Sure - that may well be the explanation for the shoulder - although it is more likely that once an atom is

already ionized, you can't do much more with it. A new photon has to find another atom to ionize. As more atoms

get ionized, it gets more difficult for photons to find un-ionized atoms, so that could as well explain the

shoulder. It is definitely some kind of saturation process.

<p>

<i>I think you mean "when a signal (light) has more dynamic range than the channel (film in this case)."</i>

<p>

No, I meant what I said. If the signal has more dynamic range, there is no latitude at all; the signal

<i>will</i> clip. Latitude is the equivalent (in electronics) of headroom. If the signal is already larger than

what the system can handle, you have no headroom. Here is the wikipedia article on latitude. <a

href="http://en.wikipedia.org/wiki/Exposure_latitude">http://en.wikipedia.org/wiki/Exposure_latitude</a>. Even

they clearly state (about latitude), "It is not to be confused with dynamic range, which is, in photographic

context, the range of light intensities a medium can capture."

<p>

And this is not about semantics at all. It is about accurately defining what we are talking about. Dynamic range

is a ratio. Linearity is a curve shape. Latitude is an error margin. They may all be related, but they are quite

different things.

<p>

Toe and Dmin and shoulder and Dmax are symmetric phenomena. You can linearize <i>both</i> and extract detail at

both clipping ends. So, whatever applies to one in general applies to the other. Since the Ektar curves don't

show a shoulder (wonder why, Kodak?) I just used the toe curve to illustrate. That doesn't mean that a shoulder

doesn't exist or that it behaves different from the toe.

<p>

<i>That, tied in with the linear region, would by its very definition simulate a variable gain amp.</i>

<p>

Of course there is a variable gain amp there - but it is the nonlinear part, not the linear one. That's exactly why

I've been saying that you would extend dynamic range if you linearized that region. But from all the curves, what

you see is a huge linear region and a small non-linear region, that if recovered would give you a half stop (or

maybe a full stop). Compared to 13 stops of linear region, this is not the significant factor in dynamic range

comparison - such as 13 stops for film, 8 for digital. If you linearized, you'd get what 13.5 for film, and 8 for

digital. Significant difference? Not from where I stand.

<p>

Then I pointed out that digital relies on a charge accumulation device as an optical sensor - this will also have

soft clipping - or a curved shoulder, so you could probably extract the same half stop or so from digital, which

means 13.5 stops for film and 8.5 stops for digital.

<p>

Now to tie it all together - if you're going to compare a 13 stop range to an 8 stop range, both in the linear

portion, then the theory that explains the difference can't rely on non-linearity (log response etc). What is the

actual theory? In my mind, none - dynamic range is a characteristic of the system design itself; the 8 stop range

for digital is a limitation of current design, and soon you'll see 13-14 stop ranges if not more.

<p>

As for film - the whole thing - silver halide, development time etc., forms a system with some dynamic range. Why it

can't be more is something that I have no idea about, but sure, if you made a blacker black (denser Dmax) and

decreased base fog, why, you'd have more dynamic range. How to do it? No idea.

[rishij]

Bernie:<i>"but lets assume that development initiation is directly linearly related to number of silver at a sensitivity site."</i>

<p>

You mean 'inversely linearly related', yes?

<p>

Bernie:<i>"Did any of that make sense?"</i>

<p>

Yes, actually, it did. Assuming that you meant that the linear relationship was, in fact, inverse. That is, the more 'developed' a speck is, the lower the initiation time. Which I'm sure you did. I can read in between the lines :)

<p>

However, your premise that "development initiation [delay] is directly [inversely] linearly related to number of silver at a sensitivity site" is a big <b>IF</b>. Chemically, I would have to say that the reduction potential at a sensitivity site shouldn't change that much based on 10 vs 50 vs 100 reduced silver metal atoms making up a 'clump'. What <b>would</b> change, however, would be the number of 'paths' along which electrons could travel to reduce other AgBr ions in the crystal. The more silver metals atoms you have in the clump to begin with, the more paths the electrons from the reducing agent (developer) could travel upon to reduce more AgBr ions within the crystal. Therefore, the faster and more extensive would be the resulting silver speck growth upon development.

<p>

Now, if there's a non-linear relationship between the number of silver atoms (metal) at a clump and the number of paths available for electrons to travel along into the interior of the silver halide crystal (directly proportional to 'access' to internal AgBr ions for reduction), which itself (the # of paths) is proportional to the surface area of the clump (of reduced metal silver atoms) exposed to non-reduced silver ions within the AgBr crystal, then this would explain the non-linear response of film. If that's true to begin with :)

<p>

Whoa, my head hurts. Again. But that may be a lead. I need to think about it. Or someone else does. Damn we should form a think tank.

<p>

Rishi

[vijay_nebhrajani]

<i>Bernie: But do we actually know this?</i>

<p>

Well, we know that the response of film is linear - so I'm saying that it is axiomatic that the response of a single silver halide crystal is also linear, because I can't imagine how non-linear elements could, when put together in an emulsion become collectively linear. Beyond that, I make no statement. That whole 10/20 and 100/200 ion thing was just a contrived example.

[rishij]

Vijay:<i>"although it is more likely that once an atom is already ionized, you can't do much more with it. A new

photon has to find another atom to ionize."</i>

<p>

Oh, boy, Vijay. Ionize? Are you kidding me? There's no ionization going on. There's the reverse of ionization.

Knocking an electron off a bromine ion and making it a bromine atom. What we care about is how many silver ions

are 'reduced' to silver metal by accepting said electron. Technically, it's called 'photolysis'.

<p>

Vijay:<i>"As for film - the whole thing - silver halide, development time etc., forms a system with some dynamic

range. Why it can't be more is something that I have no idea about, but sure, if you made a blacker black (denser

Dmax) and decreased base fog, why, you'd have more dynamic range."</i>

<p>

Huh?? No one here cares about the dynamic range of the film. We care about the range of intensities

<i>discernible</i> that were recorded from the original scene. The dynamic range of the film itself we can

stretch out to whatever the heck we like in a 16 bit file in Photoshop. Or, heck, a 32 bit file.

<p>

Vijay:<i>"No, I meant what I said. If the signal has more dynamic range, there is no latitude at all; the signal

will clip."</i>

<p>

Right, but, in this thread, we're only interested in scenes that have a range of luminosities greater than that

recordable by the medium. So, yes, the signal will clip. Either in the highlights, or the shadows. So, in all

cases here, we're talking about negative exposure latitude, if I understand the terminology correctly. The

question is: which system has a lower magnitude of negative exposure latitude (i.e. closer to '0')? I think the

answer is negative film.

<p>

Rishi

[vijay_nebhrajani]

<i>Mauro: "No no no.... I know you must understand it but it's just late.

<p>

Please go to the link I sent you, pull a few points from the graph, and plot them in Excel on a linear axis. Then

please, let me know what you conclude."</i>

<p>

Well, I don't use M$ stuff, so I'll dig up some graphing tool for this if I can, but I did a quick plot on paper.

I expanded the X axis by taking 10 to the power of the numbers; and did the same for the Y axis. What I have is

the X axis reads - 0.001, 0.01, 0.1, 1.0, 10 and 100. The Y axis reads: 1, 10, 100, 1000, 10,000. This

corresponds to densities of 0, 1, 2, 3 and 4. I draw this, and it is still a straight line.

<p>

The point is, density is a logarithm itself in the plot, so I expect to see a straight line, and I do. What am I

missing?

<p>

Maybe you're not expanding the Y axis? If so, then you <i>will</i> see a logarithmic response, but that is

because the Y axis is already a logarithm. Don't believe me - tell me, is the ratio of the blackest black to the

whitest white 4:1? Because a density of 4 is the blackest black, and this is certainly not 4 times less bright

than the whitest white - it is in fact 10,000 times less bright.

<p>

Based on the plot, what I see is if I increase the exposure 10 times, my density increases roughly 8 times or so

(rough paper plot); same slope throughout. That's linear, since y/x = a constant.

<p>

Maybe I'm missing something else - will wait for you to explain.

[vijay_nebhrajani]

<i>Rishi: "Oh, boy, Vijay. Ionize? Are you kidding me? There's no ionization going on. There's the reverse of

ionization. Knocking an electron off a bromine ion and making it a bromine atom. What we care about is how many

silver ions are 'reduced' to silver metal by accepting said electron. Technically, it's called 'photolysis'. "</i>

<p>

I stand corrected. You are right of course. The point remains though; once you have silver atoms and bromine

escapes, newer photons have to find bromine ions; which are getting scarcer as exposure progresses. This was

actually in support of your point about non-linearity. I was merely stating that this process could very well be

responsible for the eventual shoulder.

<p>

<i>Huh?? No one here cares about the dynamic range of the film. We care about the range of intensities

discernible that were recorded from the original scene. The dynamic range of the film itself we can stretch out

to whatever the heck we like in a 16 bit file in Photoshop. Or, heck, a 32 bit file. </i>

<p>

My turn.

<p>

Huh? What? The <i>"range of intensities discernible that were recorded"</i>? This is the very definition of

dynamic range. A range is a max and a min. Dynamic range expresses this as a ratio. It is called Dynamic

<b>range</b> for a reason.

<p>

<i>Right, but, in this thread, we're only interested in scenes that have a range of luminosities greater than

that recordable by the medium. So, yes, the signal will clip. Either in the highlights, or the shadows.</i>

<p>

You brought up latitude. As far as I have been following this thread, I have always spoken about dynamic range.

The title of the thread is also "Dynamic Range".

<p>

<i>The question is: which system has a lower magnitude of negative exposure latitude (i.e. closer to '0')? I

think the answer is negative film. </i>

<p>

The question is which medium has greater dynamic range (you may frame this as "which medium gives you the

greatest margin for error?", but that just implies a greater dynamic range. No semantics - this is just about

correct definitions.) And you are right about the answer - it is unquestionably negative film.

[bernardwest]

Come on you two, let's not go crazy like in that last thread. I think you are actually in agreement here. What Vijay says about film being linear is right (I think), except for the tiny bits of the graph which correspond to the toe and shoulder. So he wasn't being exactly precise in his language, but he is right to say (I think) that to linearize the non-linear sections wouldn't add much to the DR of the film. Surely we all agree on these points? And we all agree that negative film has more DR than a 40D. So I don't even know exactly what you two are arguing with each other about. Now, make up and be friends, before Vijay starts playing reductio-ad-absurdum :)

[vijay_nebhrajani]

Now, make up and be friends, before Vijay starts playing reductio-ad-absurdum :)

 

ROTFLMAO :))))

[rishij]

Sorry, I thought perhaps you were being tricky & talking about the dynamic range of the dyes on the film. Is there a different

term for that?

 

As for bromine ions becoming scarce with increased exposure? Not a chance. There are orders of magnitude more bromide

ions than even the highest number of reduced silver metal atoms possible for a fully exposed latent site; indeed, if it weren't so, then

a fully exposed negative would look black prior to development, & we know that's not the case (reductio ad absurdum

anyone? :)

 

Bernie, sure Vijay & I are in agreement because Mauro did a convincing job here! But, we aren't in agreement as to the

HOW (actually, I haven't heard a 'how' theory from Vijay yet). I agree that in the most usable range the response of film is

linear; but I doubt it is on the upper end. If you & Vijay are claiming that the non-linear response on the upper end doesn't

afford you much usable information, then how do you explain the presevation of highlight detail in negative film?

[mauro_franic]

Some post holiday bonding again? Yeepe.

[mauro_franic]

Vijay, by the way you are right, I was looking at the first toe and the line straightening afterward so I was assuming the density axis as linear. Then the actual real toe is in the shadows and the highlights are then pushed out?

 

Like Bernie said, I think we all agree on the facts, what is you explanation for them?

 

Yesterday I tool some TMX nature pictures I developed in Xtol. Which expands the midtones and cuts the shadows and the highlights. Well I realized that I had taken the DRange test with TMX in the same roll and although I was expecting the highlights/shadows to be gone, a quick scan revealed they are like almost the same as the Ektar shots. (I will post later). That means you can comfortably add at least 1-2 stops on each side when developed with Tmax.

[mauro_franic]

Anyone in the Atlanta area with the 5DII yet? I would like to do a follow up on both dynamic range and resolution comparing Ektar, Velvia and TMX to the latest FF DSLR.

 

Ellis?

[dippe1]

It is interesting to see that this forum seems much more mature than fotosidan.se (Sweden) where mentioning Ken

Rockwell immediately made me an outcast in the same thread I started there a month or so ago. Here somebody

thought KR shouldn't be the only source of info. That is much more sensible and I agree on that but despite that he's an

excellent photographer and his level of knowledge surpasses most of the members at photo.net (how many of us have a

US patent in the field of photography?).

Please keep up the good habit of not killing the threads by being "besserwissers" (smart-asses)!

Enjoy your thinking!

Cheers

[vijay_nebhrajani]

<i>Rishi: As for bromine ions becoming scarce with increased exposure? Not a chance. There are orders of magnitude more bromide ions than even the highest number of reduced silver metal atoms possible for a fully exposed latent site; indeed, if it weren't so, then a fully exposed negative would look black prior to development, & we know that's not the case (reductio ad absurdum anyone? :) </i>

<p>

OK, here's the reductio-ad-absurdum, since you asked for it. If there are orders of magnitude more bromide ions than reduced metallic silver, then that metallic silver can't be significantly blocking light and causing non-linearity now, can it? Unless it were at the shoulder, if then. (I don't think that this is true even at the shoulder, but that's my "theory", and I'll explain it in a bit.)

<p>

Anyhoo, the question is moot, since we are all in agreement that film has <i>linear</i> response, as I said a long time ago. Mauro agreed to this, didn't he?

<p>

<i>Bernie, sure Vijay & I are in agreement because Mauro did a convincing job here! But, we aren't in agreement as to the HOW (actually, I haven't heard a 'how' theory from Vijay yet). I agree that in the most usable range the response of film is linear; but I doubt it is on the upper end. If you & Vijay are claiming that the non-linear response on the upper end doesn't afford you much usable information, then how do you explain the presevation of highlight detail in negative film?</i>

<p>

Whoa, whoa, slow down. Mauro did a convincing job about demonstrating that negative film has the greatest dynamic range, absolutely. But that's suggesting that this wasn't already known. Look at any of dpreviews tests - digital has barely 9 stops, and anyone who has used negative film knows that the dynamic range is at least 12-13 stops if not more. Indeed some people routinely overexpose portraits (controlled lighting - subject DR is significantly lower than film DR) by 2 stops to get "creamy skin tones".

<p>

Preservation of highlight detail? Well, if it falls within the dynamic range of film it will be preserved. What's so difficult to understand about that? With soft clipping, you can recover a little extra information by linearizing the clipped region, but I don't see how that is more than the half odd stop or so. Once light increases to the point where you get into the flat part of the curve past the shoulder, all detail is lost, because density has hit max. Alternately once light decreases to the point that you cross the toe and get into the flat part of the curve, all detail is lost because density has hit min.

<p>

Dynamic range is a characteristic of the system itself, so there is nothing to explain here. If film preserves highlight detail for another half stop, then by definition, dynamic range is a half stop greater. Once again, this has nothing to do with the curve shape - it is the ratio of the max to min; if by linearizing or whatever, the max can be increased and the min decreased, then by all means, calculate the ratio of the increased max to the decreased min - and that is your dynamic range.

[vijay_nebhrajani]

<i>Mauro: Vijay, by the way you are right, I was looking at the first toe and the line straightening afterward so

I was assuming the density axis as linear. Then the actual real toe is in the shadows and the highlights are then

pushed out?</i>

<p>

Right - the density axis is itself logarithmic. So Ektar 100 has a 13 odd stop <i>linear</i> range. The toe is in

the shadows and the shoulder is in the highlights, but there is a vast 13 stop range that is linear. As long as

your subject's dynamic range is less than 13 stops, this will fit neatly in the 13 stop linear region (assuming

you get your metering right, of course). If like your dead roses picture, the dynamic range of the scene exceeds

the linear plus toe and shoulder regions, then some parts will either go all black or all white. This is

clipping.

<p>

Now you can "extract" some highlight detail and some shadow detail because a part of those are on the

curved heel and toe. In a scan you can use photoshop to selectively manipulate highlights or shadows; and with

conventional, enlarger based printing, you can burn or dodge. These are all techniques to linearize the shoulder

and toe; to extract that last drop of detail.

<p>

As I said, this may get you a half or even a full stop of "extra" shadow or highlight detail but my points are that

<p>

a) That extra half or full stop is also part of the total dynamic range (after curve shaping or whatever) by

definition. So if you actually manage to get 14 stops out of Ektar after linearizing the toe and shoulder

response, then its dynamic range is 14 stops by definition.

<p>

b) That extra half or full stop is not much compared to the 13 full stops of linear range. (It may be important

because you don't want to blow out the bride's dress etc., but it is not significant magnitude-wise.)

<p>

c) Digital uses charge storage (capacitive effects), so it may be possible to extract a half stop extra from

digital as well, but that is

moot, given that the inherent dynamic range for digital sensors is only 8-9 stops compared to 13 stops for film.

Expressed as a ratio, film has a DR that is (4-5 stops = ) 16 to 32 <i>times</i> greater than digital even if you

were to ignore the toe-shoulder non-linearity effects.

<p>

d) Point c) is true regardless of curve shapes.

<p>

That's all I was trying to say. Hope it makes sense.

[mauro_franic]

Vijay, "Anyhoo, the question is moot, since we are all in agreement that film has linear response, as I said a long time ago. Mauro agreed to this, didn't he? "

 

I said if both axis are logaritmic, and there is a kink in the graph, then the logaritmic response happens earlier inbetween the shadows and the highlights.

 

Here it is with both axis linear:

http://shutterclick.smugmug.com/gallery/6616619_YJEwK#428460601_tWtTf-A-LB

 

"Mauro did a convincing job about demonstrating that negative film has the greatest dynamic range, absolutely"

 

No arguments there, ha ha

 

"But that's suggesting that this wasn't already known. "

 

Ektar was just released, so a) there is no direct comparison I know of b) I haven't seen other test that graphically show photographers the problems of the -known- limited dynamic range.

 

"Dynamic range is a characteristic of the system itself, so there is nothing to explain here. If film preserves highlight detail for another half stop, then by definition, dynamic range is a half stop greater. Once again, this has nothing to do with the curve shape"

 

True. You could have a wider DR with a system that is also linear. It just so happen that in this case it is not linear.

[mauro_franic]

Vijay, I just saw your follow up. I think we are all pretty much in agreement.