F-Stop Range of Digital Photography?

The problem is, the "dynamic range capability" of JUST the file
says NOTHING about the dynamic range of the INPUT that it can
capture.
Yes, you are correct. It doesn't. One of the problems of this thread is that Jason was never talking about the dynamic range of the actual original scene that might be photographed, but everybody presumed he was, including me at first.
You are correct, of course. But this "dynamic range capability"
of JUST the file ONLY tells you how many subdivisions you can make
from a given input source.

Let's use a ladder analogy. The dynamic range of the input is how
high it is from ground level to the roof of the building I want to
get to.

The dynamic range of the ladder (as you define it) is simply the
number of steps I am allowed to have on the ladder.

No matter HOW HIGH the building, a 10-step ladder can be made to
reach the top of the building. However, those steps may be too
large to be of any practical use for a human to use that ladder
effectively.

If I want the steps to be 1 foot apart, though, THEN a larger
dynamic range ladder (more steps) is required to reach a larger
dynamic range (more height) building.

But without the restriction of "steps must be closer than 1 foot
from each other", the dynamic range of the ladder (number of steps)
says nothing about the dynamic range of the building (height) that
I can build a ladder to reach.
This has NOTHING to do with what we're talking about. Mapping of
bits to arbitrary EV values (compression, expansion, gamma,
contrast) does NOTHING to change the dynamic range capability of
THAT FILE. Once again, the scene or music, or the input source
has nothing to do with the dynamic range capability of a certain
number of bits, eg. a file format.
--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise
 
It's not really silly.

Like I said , expressing the range in f-stops is the most common
because we all speak that language. That's the language the
original poster was speaking in. He has a scene he wants to record
and it may have a greater Scene Brightness Range than his camera's
Capture Range can acquire.
Yep, that was the topic of the original poster. Things got on a small tangent as they tend to do. The poster's original question was answered in other parts of the thread, so no big loss to him I hope.
(see, I didn't say " Dynamic Range" ;)
I've got nothing against using that word to describe it... we just need to be clear what we're talking about, and understand that there are a dozen points along the path of digital photography to measure dynamic range. As you know I like a different word to describe it, but I can accomodate. :)
And bit-depth does nothing at all to increase that Capture Range.
Agreed, I made 3 and 5 bit samples files above to show this.
However, your use of the term is also correct, in that higher
bit-depth in a file can potentially hold a higher Output Range? Is
that what you mean?
Correct.
 
Yes, you are correct. It doesn't. One of the problems of this
thread is that Jason was never talking about the dynamic range of
the actual original scene that might be photographed, but everybody
presumed he was, including me at first.
Sorry about that, it was easy to miss. Here's my first post, where this all got started:

************

That's the great thing about digital, just keep adding more bits and you've added dynamic range. A 16 bit/channel Tif has a whole lot of dynamic range. A 64 bit/color tif would have even more (assuming a constant color space)

Now, you probably actually want the dynamic range of a sensor of some particular camera, or perhaps of some format (eg. 8 bit jpeg). Which sensor/camera are you asking about?

Jason
*************

My point was, there are a lot of steps in a photographic process, and you need to be specific about each one you're talking about. I don't think there was an answer to which sensor or camera system he was wondering about (if any). I feel the file format's dynamic range is becoming more important as we big to get superior dynamic range files from our cameras. 8 bits just isn't going to cut it forever.
 
These small tangents, as long as they are presented by folks, like yourself, who are not out to flame and complain, are what makes things interesting.

(Now if only the political debates I've been watching lately were like this...Ha!)

I've been in the photo business (and the digital end of it's development) for a very long time and it's always helpful to get a new perspective. Sometimes we all need to step back and listen.

And on that note, lunch is over and it's back to work time...

Keep truckin'
Yep, that was the topic of the original poster. Things got on a
small tangent as they tend to do. The poster's original question
was answered in other parts of the thread, so no big loss to him I
hope.
 
Maybe not misleading, but certainly ambiguous.

"That's the great thing about digital, just keep adding more bits and you've added dynamic range. A 16 bit/channel Tif has a whole lot of dynamic range. A 64 bit/color tif would have even more (assuming a constant color space)"

That's very easy to misinterpret as "all you need to do to have more dynamic range in your photos is to buy a camera that supports more bit-depth". (In spite of your other verbage).

I think it's easier to understand if one express the SENSOR as being able to capture a particular dynamic range, with the camera file system having more bit-depth to give you more "tonality", as somebody else expressed it.

That extra "tonality" (bit-depth, dynamic range) in the file format is what enables you to dig out the buried detail in the shadows.

--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise
 
Hi Jason:

I have finally figured out why you have a misconception about the dynamic range of an image file. It was your comment about working with digital data analysis that did it.

Well, lets say we have some sensor set up measuring some sort of event. Then the sensor will give a signal each time this event occurs, and we want to store the counts in a data file. Since we are talking about events, they can be represented by integer numbers, and we want our file to be able to represent all the possible number of events.

Then, if we are using 8 bits to count the events we will be able to count from 0 to 255, if we are using 10 bits, we will be able to count from 0 to 1023, if we are using 16 bits we will be able to count from 0 to 65535. Obviously, adding bits adds more “dynamic range” to our analysis.

But the bits in an image file are not representing events or integer values of luminosity. They are representing tones of luminosity going from black to white. And white does not get any brighter because we are using a greater number to represent it. Thus, for a B/W image, if we are using 8 bits to represent this tonality from black to white it is described in 256 steps, if we are using 10 bits it is described in 1024 steps, and if we are using 16 bits it is described in 65536 steps (and so forth). But the dynamic range is the same – going from black to white.

And as mentioned in a previous post, the final luminosity of black and white will depend on software and hardware.

--
Kjeld Olesen
http://www.acapixus.dk
 
I also wanted to add that we can all (all on both sides) be "proud" for having conducted this debate in a polite manner (or at least so I think) dispite our difficulties of reaching a concensus.

--
Kjeld Olesen
http://www.acapixus.dk
 
That's very easy to misinterpret as "all you need to do to have
more dynamic range in your photos is to buy a camera that supports
more bit-depth". (In spite of your other verbage).
Luckily, the manufacturers tend** to use a format that efficiently matches their camera (so far). For instance, we've yet to see Canon come out with 16bit RAW files for the G3. Why? No need, just a waste of space with that sensor. They'd still have less true dynamic range than say a 1D (any way you measure it) We can't say the same for the $29 scanners obviously.

I thought it was pretty clear that I was talking about a tif format's dynamic range as a function of bits though, but of course I wrote it, so it should seem clear to me.

Jason
 
Now, in addition to teaching you DSP, I have to explain chemistry
to a biologist!

ph =-log10[A] where denotes the concentration of A

Notice how a zero input blows up the formula! The log assures you
don't divide by 0 by not being defined for zero.

Do you see now how the dynamic range is defined as the ratio of the
largest signal to the smallest signal .
Well, let me constrain myself to saying that you got this one wrong to. A pH of 0 would mean that the input (A) to log10 was 1, so no formula is blown!

And I know well that pH is a log scale (in fact I work at the institute where the pH scale was defined originally in the first place), but I used it to illustrate how by using numbers ranging from only 0 to 14 you can represent a "dynamic scale" of 10^14th.

Man, you are stubborn!

--
Kjeld Olesen
http://www.acapixus.dk
 
What I write is always crystal clear to me. Well, at least for a few minutes, anyway. LOL.
I thought it was pretty clear that I was talking about a tif
format's dynamic range as a function of bits though, but of course
I wrote it, so it should seem clear to me.
--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise
 
I have finally figured out why you have a misconception about the
dynamic range of an image file. It was your comment about working
with digital data analysis that did it.
I believe you've accurately described a big part of our differences in views. However, believe me, I don't have any misconceptions about the topic. I'll try to describe below.
Well, lets say we have some sensor set up measuring some sort of
event. Then the sensor will give a signal each time this event
occurs, and we want to store the counts in a data file. Since we
are talking about events, they can be represented by integer
numbers, and we want our file to be able to represent all the
possible number of events.
What you've done here, is sampling "digital" data. There was no analog to digital conversion required. What this gives you, is "perfect" data.

Now, here's the important part:

However, when we're talking about a file format, we do not know where the data came from. We can't put a limit on a file format because the data it might have been sampled to a limited resolution. The fact is, the format can hold a certain dynamic range.

This is the same as Phil giving us a signal to noise ratio of a camera by merely looking at it digitally. He's not going through the digital to analog conversion that MUST be used to ever view it with human eyes. However, it's still useful to us, because it represents a maximum theoretical value we might obtain with the right hardware.
Then, if we are using 8 bits to count the events we will be able to
count from 0 to 255, if we are using 10 bits, we will be able to
count from 0 to 1023, if we are using 16 bits we will be able to
count from 0 to 65535. Obviously, adding bits adds more
“dynamic range” to our analysis.
But the bits in an image file are not representing events or
integer values of luminosity. They are representing tones of
luminosity going from black to white. And white does not get any
brighter because we are using a greater number to represent it.
Thus, for a B/W image, if we are using 8 bits to represent this
tonality from black to white it is described in 256 steps, if we
are using 10 bits it is described in 1024 steps, and if we are
using 16 bits it is described in 65536 steps (and so forth). But
the dynamic range is the same – going from black to white.
Once again, I feel I should point out, that the difference (ratio) between black and white in a file format is infinite (actually undefined because you're dividing by zero). Does this mean that the scene had infinite dynamic range? Nope, because there is sampling error (which I think you've referred to) This sampling error happens to go back to the Dmin and Dmax values, but we should avoid that for now. :)
And as mentioned in a previous post, the final luminosity of black
and white will depend on software and hardware.
Yes, the luminosity to be seen by our eyes absolutely requires a digital to analog conversion somewhere. As I mentioned, since I'm talking about the digital format, this conversion doesn't apply. I hate to repeat myself, but I feel this is valid for the same reason that Phil's signal to noise ratio is a valid measurement (although that's not the only reason)

Jason
 
Well, let me constrain myself to saying that you got this one wrong
to. A pH of 0 would mean that the input (A) to log10 was 1, so no
formula is blown!
No, no, no. That's not what I am said. If you input a 1 into that function, you get a PH of 0. No big deal. However, you can't input a zero into that function, or it blows up. It blows up for precisely the same reason you can not divide by zero.
Man, you are stubborn!
Yeah, a bit stubborn (Irish) but I know this stuff.
 
OK, I admit it was a little more involved than I first thought and all the ideas about using Photoshop have helped me to accomplish my first goal. However, now I am just curious. Is there a concise answer to this question?
Another in a series of technical questions:

I'm not sure if I read or heard that film has about an 11 stop
range; meaning that it can differentiate contrast accross that
range. Not being sure if this is even a correct statement; do you
know what the range is for digital photography? My practical use
is for spot metering in long-exposure photography.

--
T Blair
Gear: D60, EOS3, G1, 16-35, 28-70,
70-200 2.8, 85 1.8, 550EX, 420EX
--
T Blair
Gear: D60, EOS3, G1, 16-35, 28-70,
70-200 2.8, 85 1.8, 550EX, 420EX
 
OK, I admit it was a little more involved than I first thought and
all the ideas about using Photoshop have helped me to accomplish my
first goal. However, now I am just curious. Is there a concise
answer to this question?
There is a concise answer to a concise question. I'm not sure you've even narrowed down your question to a particular camera? Digital photography is a wide field.

This camera that someone else has linked to, can capture 17 stops. Probably about as good as it gets right now. Things are constantly improving (we can hope) though.

http://www.dpreview.com/news/0105/01051003blincdigitalcamera.asp
 
Oh, wow.

17 stops.

Now, give me that with clean data at ISO 6400, and about 11 million pixels, for a price of 3 grand, in a 1D body. ;)
This camera that someone else has linked to, can capture 17 stops.
Probably about as good as it gets right now. Things are constantly
improving (we can hope) though.

http://www.dpreview.com/news/0105/01051003blincdigitalcamera.asp
--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise
 
What is the exposure range, in number of f-stops, for a D60?
OK, I admit it was a little more involved than I first thought and
all the ideas about using Photoshop have helped me to accomplish my
first goal. However, now I am just curious. Is there a concise
answer to this question?
There is a concise answer to a concise question. I'm not sure
you've even narrowed down your question to a particular camera?
Digital photography is a wide field.

This camera that someone else has linked to, can capture 17 stops.
Probably about as good as it gets right now. Things are constantly
improving (we can hope) though.

http://www.dpreview.com/news/0105/01051003blincdigitalcamera.asp
--
T Blair
Gear: D60, EOS3, G1, 16-35, 28-70,
70-200 2.8, 85 1.8, 550EX, 420EX
 
Oh, wow.

17 stops.
I don't know if this is the same concept but some CCD manufacturer was talking about making a sensor that had groups of pixels with different sensitivities. You could have a pixel set to ISO 100, and two pixels next to it set to 400 and 1600. After exposure, the image is built from the pixels that were properly exposed and the rest are thrown away. This was intended for situations where resolution wasn't as important as having proper exposure for a wide range of lighting situations (like a security camera).
 
I haven't measured my D60 in objective way for dynamic range, but here's my gut feel, for what it's worth.

The camera can capture about 7 or 8 stops at ISO 100. The dynamic range of digital cameras goes down with ISO (there are exceptions like the 1D at ISO 100 due to CCD saturation), as the shadow detail gets swamped out by noise at some point. Positive exposure compensation from the RAW format is very useful at ISO 100, but gets less useful because of noise at higher sensitivities.

One of these sunny days, I'd like to compare the D60s dynamic range compared to my eyes. I've got a test setup in mind, with a similar object in both full sunlight, as well as deep in shadows.

Jason
OK, I admit it was a little more involved than I first thought and
all the ideas about using Photoshop have helped me to accomplish my
first goal. However, now I am just curious. Is there a concise
answer to this question?
There is a concise answer to a concise question. I'm not sure
you've even narrowed down your question to a particular camera?
Digital photography is a wide field.

This camera that someone else has linked to, can capture 17 stops.
Probably about as good as it gets right now. Things are constantly
improving (we can hope) though.

http://www.dpreview.com/news/0105/01051003blincdigitalcamera.asp
--
T Blair
Gear: D60, EOS3, G1, 16-35, 28-70,
70-200 2.8, 85 1.8, 550EX, 420EX
 

Keyboard shortcuts

Back
Top