200d iso setting


pete

Link Posted 23/05/2010 - 23:21
I have the ISO set to auto on my K200D (range 100-800). While fiddling with the settindgs I noticed that by using FN key another iso range is selected 200 - 800 200%. Does anyone know what this is/means because I cannot find reference to it in the manual (unless iv'e overlooked it)

pentaxanne

Link Posted 23/05/2010 - 23:23
its to do with the dynamic range.

Anvh

Link Posted 23/05/2010 - 23:31
highlight and shadow recovery can not be done with ISO 100 for some reason, most likely dynamic range like Anne said
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ

rkt

Link Posted 23/05/2010 - 23:44
Yup, that's correct, page 84 of the pdf version K200D manual... under "Shooting Functions" ... titled "Expanding the Dynamic Range" ...
regards,
rkt

flossie

Link Posted 24/05/2010 - 08:01
afaik the "expanded" ISO settings are basically fake - they are some (non-reversable) electronic processing to the picture, rather than any change in sensitivity.

For the next discussion, why do DSLR's have "ISO" anyway, time a more appropriate and meaningful measurement was used like dB, as used on video cameras, and the difference between still and moving digital cameras is coming less than the difference between film and digital...
Still shooting in the dark (literally and metaphorically)...

terje-l

Link Posted 24/05/2010 - 09:34
ISO is a convenient way of expressing light sensitivity, since doubling the ISO setting corresponds to one f/stop or halving the exposure time. Also it is directly related to film sensitivity (the old ASA figures).

I am perfectly aware that you don't change the sensitivity of the sensor, but merely increases the amplification of the signal (hence the increased noise ah higher settings).

Anyway, I see no reason at all for changing ISO to dB or another unit of measure, ISO is well known, easy to relate to, and convenient. And to be honest, I think there is more difference between still photographers and movie makers than between equipment.
Best regards
Terry

K20D, Optio I10, DA 18-55 1:3.5-5.6 AL II, A 1:1.7/50, D FA 1:2.8/100 Macro, Sigma 70-300 1:4-5.6 APO DG Macro, Pentax AF 360FGZ

Mongoose

Link Posted 24/05/2010 - 16:54
flossie wrote:

For the next discussion, why do DSLR's have "ISO" anyway, time a more appropriate and meaningful measurement was used like dB, as used on video cameras, and the difference between still and moving digital cameras is coming less than the difference between film and digital...

simply because that's what film is measured in, and there's no particularly good reason to change it.

The true sensitivity of the sensor is given by its quantum efficiency, but this has no useful meaning in photographic terms. Why learn a whole new system when there is one in place which does the job perfectly well?

The most flexible solution would be to have a massive bit depth on your ADC so that you could effectively operate at all ISOs at once and just pick which part of the file to develop as a displayable 8bit JPG. That might get pricey though, and would result in RAW files of truely epic proportions.
you don't have to be mad to post here



but it does help

flossie

Link Posted 24/05/2010 - 17:15
Hmm, I agree with you to an extent - but it doesn't give any information about what the "optimum" level for a particular camera would be. For a random example, looking at 1600 ISO on a K-7 (base 100) it is +12dB of gain, but on a K-x (base 200) its +9dB - (could this be part of the explanation of the better performance of the Kx in low-light...?).

Television and Video cameras have always been calibrated in dB. low/mid-budget production has pretty much completely moved away from film now, and anyone under the age of about 35 has probably never shot film in their life - so its an increasingly alien concept to many people that they can't relate to...

Take this pretend conversation with a 20-something :

"my pictures are too dark but I don't want to go any slower"
"you need to increase the ISO equivalency of the sensor"
"errr...you wot?"
- vs -
"you need to put some gain in the sensor"
"ah! I see"


In particular it would be easier to see the relationship between f-stop and gain that way...


But hey, why stop there - we could go the whole hog and describe lenses by their magnification instead of their focal length! That's another thing video gets right...
Still shooting in the dark (literally and metaphorically)...

montyaus

Link Posted 24/05/2010 - 18:22
Flossie you mention magnification in cameras, when I was doing target shooting,it was explaned to us, that a good 4x scope was all that was needed, any larger magnification would not give as clear an image in heat haze or other climatic conditions,(we would shoot over 1000 yards) where as 4x would not be affected as much it seemed to punch through giving a clear picture,could this be the reason, SLR are lower power
K5iis,K7,KM, MG, Super A, MZ50.
24f2.8; 28f2.8;31 limited; 35f2; 55f1.8; 135f2.8; 400f5.6:
Some zooms

Mongoose

Link Posted 24/05/2010 - 18:44
magnification is a very dificult term to quantify, that's a whole different can of worms!

I think you have explained yourself why switching to dB would be a very bad idea. Imagine trying to explain to a newbie why he had to shoot at +9dB with his K-x when his more experienced friend with a K-7 was using +12dB in the same conditions with the same aperture and shutter speed. It's hard enough for people to grasp the black art that is exposure to begin with, without making it more complex.

I agree that "you have to increase the ISO equivalency of the sensor" is a pretty dificult sentance to understand unless you know what's going on, but "you need to increase the sensitivity" works fine whatever unit you're using for that measure.
you don't have to be mad to post here



but it does help

johnriley

Link Posted 24/05/2010 - 19:03
When you think of the difficulty in circulating information, to change photography from ISO values and magnification would take decades to do. Would it add anything to photography to do it, that was really of value?

There is a native ISO rating for cameras, and I understand that it is ISO200 for Pentax DSLRs. That's the setting I normally use, but not for that reason, simply because on film it seemed a reasonable compromise between quality and making sure hand held shots were sharp.

On digital it seems to also deliver the goods.
Best regards, John

pete

Link Posted 24/05/2010 - 22:20
Having read the correct bit in the manual this setting does expand the dynamic range. It also states that this makes it more difficult for bright areas to occur in an image. So should this setting be the default? or should the auto setting be the default? What conditions would dictate that switching to "expanded dynamic range" would be preferable.
I'm struggling to get a grasp of this, so any help advice would be very welcome.

Anvh

Link Posted 24/05/2010 - 22:22
Only if you shoot JPG and want to tone down the highlights a bit for RAW it does not make a difference I believe.
Stefan


K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
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