Exposure compensation

"sonsdad" wrote in message

Hi
Can someone explain to me about the need to reduce the aperture with a digital camera to give more ‘punch’. Also how does this relate to Exposure compensation and Exposure value (if at all)

I see a complex possibility of answers because the question is vague, but no worries. When I see a question regarding aperture and an adjective like punch, sharpness, crisp, and so-forth I can only think of resolution.

So, for best resolution, you want a _modest_ aperture, typically a stop or two down from maximum (the smallest number, widest aperture). That is a general statement. Stopping down all the way increases depth-of-field, but has less sharpness due to diffraction.

You also need to be aware of the shutter speed being used. Faster is always better… up to say, 1/250 where faster than that doesn’t help most situations for sharpness. (The human body moves, has a heartbeat, and we aren’t aware of how much we move even when holding still. Maintaining a steady grip, smooth shutter release is always important.

If you means something else, then it might be about color saturation, or fidelity. Let us know what track you are on. (Another typical error is where people don’t do proper white-balance, but that’s another subject.)

For exposure compensation, try shadows and highlights under Adjustments.

Digital sensors have limited range, but worse is that they blow highlights easily. The remedy to use the above is a work-around that many appreciate.

In article ,
says…

For exposure compensation, try shadows and highlights under Adjustments.
Digital sensors have limited range

Most of the reading I have done concludes that digital sensors have a *larger* dynamic range than most film.

—
reverse my name in email address

"Jason" wrote in message

In article ,
says…

For exposure compensation, try shadows and highlights under Adjustments.
Digital sensors have limited range

Most of the reading I have done concludes that digital sensors have a *larger* dynamic range than most film.

Keep reading. 🙂

"2" wrote in message

"Jason" wrote in message

SNIP

Digital sensors have limited range

Most of the reading I have done concludes that digital sensors have a *larger* dynamic range than most film.

Keep reading. 🙂

Good advice, but it won’t change the fact … 😉

Bart

"Bart van der Wolf" wrote in message

"2" wrote in message

Keep reading. 🙂

Good advice, but it won’t change the fact … 😉

Bart, my experience is limited to Olympus – the 8mb model before the EVOLT (can’t remember which it was, but we have four of them) and Canon XL-1 digitalvideo and in both cases, blown highlights or alternatively severely compromised shadows are a big problem. I’ve no similar issues with MF or LF.

sonsdad wrote:

Can someone explain to me about the need to reduce
the aperture with a digital camera to give more ‘punch’.

What exactly you refer to with "punch" and "to _reduce_ the aperture"?

Timo Autiokari

Jason wrote:

Most of the reading I have done concludes that digital
sensors have a *larger* dynamic range than most film.

One surely can find plenty of such conclusions from the Web but they are either biased conclusions or written without better knowledge.

Film, both color-reversal and negative have about 10 f/stops dynamic range, they can capture that much of scene range. Can be seen from the film specifications. The thing is that it is not very easy to get all that image data from the film (a very high quality scanner is needed) and then the data has to be color-managed properly. Color-reversal as projected on the white-screen (or on a light-table) only shows some 5 to 6 f/stops in such way that is proper for the vision. Similarly a print that is made from negative only shows some 5 to 6 f/stops properly. But this does not change the fact that the dynamic range of the film is about 10 f/stops.

I’ve just measured the dynamic range of Canon 1D MK2 and Canon D60 dSLRs. They both have about the same dynamic range, about 8 and 2/3 f/stops. Sadly, all digital camera manufacturers conceal this very important specification. On the Web there are some reports of dynamic range measurements of digital cameras but the results are not consistent, they vary a lot. Partly this is because of some of the measurement/evaluation techniques are prone to fail considerably, partly because there is no single good standardized method available, and in some cases personal preferences seem to affect a lot. I have found only one conclusion that claims over 10 f/stops range for a digital camera, all the others conclude it it be around 9/stops.

Timo Autiokari

"2" wrote in message

"Bart van der Wolf" wrote in message

"2" wrote in message

Keep reading. 🙂

Good advice, but it won’t change the fact … 😉

Bart, my experience is limited to Olympus – the 8mb model before the EVOLT (can’t remember which it was, but we have four of them) and Canon XL-1 digitalvideo and in both cases, blown highlights or alternatively severely compromised shadows are a big problem. I’ve no similar issues with MF or LF.

Correct me if I’m wrong, but it seems to me that you are referring to the in camera JPEG results, which is somewhat like judging film capability by looking at a one hour drugstore print. Lots of information got lost.

Most decent current digicams can produce a 10 – 11 stops of dynamic range (and 1 stop of various types of noise) from its 12 bit internal processing, but you’ll need to use Raw camera data.

Film is very much limited by its grain structure which raises the noisefloor and limits the signal to noise ratio to something like 6 – 10 stops depending on whether you use slide or negative film and use low ISO.

This has all been, and no doubt will be, discussed and demonstrated on more appropriate newsgroups than this one.

Bart

Bart van der Wolf wrote:

it seems to me that you are referring to the in
camera JPEG results, which is somewhat like judging
film capability by looking at a one hour drugstore print.

This fault, that in-camera finalized JPEG shows lesser dynamic range than what can be had from the RAW, is particularly a fault in Canon cameras, all Canon models have this fault.

Do you suggest that this fault is similarly found from all the other digital cameras also?

Or do you you suggest that there would be some kind of limitation with the JPEG image format that would limit the dynamic range that it is able to show to some lesser quantity compared to what can be had from the RAW?

Most decent current digicams can produce a 10 – 11 stops of dynamic range (and 1 stop of various types of noise) from its 12 bit internal processing, but you’ll need to use Raw camera data.

While it is possible in theory (like on the Excel sheet), in the real life they do not. They do approach, with the aid of severe signal processing that produce quality issues like plastic apperance, loss of sharpness etc, about 9 stops.

Timo Autiokari

"Timo Autiokari" wrote:

While it is possible in theory (like on the Excel sheet), in the real life they do not. They do approach, with the aid of severe signal processing that produce quality issues like plastic apperance, loss of sharpness etc, about 9 stops.

9 Stops, or 2^8, or 256 levels.

"Timo Autiokari" wrote in message

Bart van der Wolf wrote:

it seems to me that you are referring to the in
camera JPEG results, which is somewhat like judging
film capability by looking at a one hour drugstore print.

This fault, that in-camera finalized JPEG shows lesser dynamic range than what can be had from the RAW, is particularly a fault in Canon cameras, all Canon models have this fault.

Do you suggest that this fault is similarly found from all the other digital cameras also?

I have not personally tested the dynamic range of JPEG output of all camera’s but there seem to be a lot of unquantified user remarks pointing in that direction. Poor exposure on Auto may also play a role in that.

Or do you you suggest that there would be some kind of limitation with the JPEG image format that would limit the dynamic range that it is able to show to some lesser quantity compared to what can be had from the RAW?

No, not necessarily so because with a proper tone curve all 12-bit raw data can be mapped in the 8-b/ch JPEG. It can be more of an issue to linearize the tone curve in order to reconstruct the linear relationship between luminance and signal level and the derived noise level which sets the floor for Dynamic range measurements. JPEGs are a more troublesome medium for DR quantification.

Most decent current digicams can produce a 10 – 11 stops of dynamic range (and 1 stop of various types of noise) from its 12 bit internal processing, but you’ll need to use Raw camera data.

While it is possible in theory (like on the Excel sheet), in the real life they do not. They do approach, with the aid of severe signal processing that produce quality issues like plastic apperance, loss of sharpness etc, about 9 stops.

That would depend on the (absence of) noise reduction and average noise floor level, but it is not difficult to exceed those 9 stops if a bit more noise is tolerated, as I’ve demonstrated (in a ‘worst’ case scenario of tungsten lighting and lots of added lens flare, and a raw converter that clips the noise below 127 out of 4096) in a more appropriate newsgroup:
< http://www.xs4all.nl/~bvdwolf/main/foto/Imatest/1dsm2/1436_S tep_2.png> ..

Bart