ISO annoyance! Pentax Kr

uberdude

uberdude

Suspended / Banned
Messages
367
Name
Tony
Edit My Images
Yes
So, had the K-r for just over a year now and I'd thought I read the manual from front to back a few times.

I had it in my head that the default setting of ISO 200 was fixed and that was it....tough.

Turns out today I read in the manual I can 'expand' the sensitivity - not just up but down too.....finally, there is an ISO 100!

Under C settings, first page, point 3. Expanded sensitivity. However, if you have highlight correction on, it can not be shifted, so that needs turning off..

Hopefully I may have some nicer shots now, but I'm not sure I'd see the difference but we will find out! :shake:
 
Why would you see nicer shots?

The native ISO is 200 which is where it will produce it's best results - shooting at ISO100 will make no difference at all (and if anything may even have a negative impact).
 
The difference between 100 & 200 ISO is the equivalent of a stop of exposure. Of course it makes a difference.
 
jon ryan said:
The difference between 100 & 200 ISO is the equivalent of a stop of exposure. Of course it makes a difference.
Click to expand...

Yes, and very handy that can be, but the expanded settings are artificially created - basically similar to taking an over-exposed shot and darkening it post processing. That is to say, you lose one stop of dynamic range at the highlights end.
 
HoppyUK said:
Yes, and very handy that can be, but the expanded settings are artificially created - basically similar to taking an over-exposed shot and darkening it post processing. That is to say, you lose one stop of dynamic range at the highlights end.
Click to expand...

Exactly, only really useful for lowering shutter speeds in bright sunshine with a fast lens, otherwise you're much better off shooting at ISO200 if image quality is what you're after.

This is why the NATIVE ISO is 200, not 100. If it could do ISO100 proper that's what it would default to.
 
Last edited:
I just don't see why it isn't 100 at default and then expand up? Surely from camera to camera the reality of the actual ISO is different anyway? Why not call 200 100 and leave it at that?

I'll try and get a range of shots in anyway using both, I'll simply have to find out!
 
uberdude said:
I just don't see why it isn't 100 at default and then expand up? Surely from camera to camera the reality of the actual ISO is different anyway? Why not call 200 100 and leave it at that?
Click to expand...

Err, because ISO stands for International STANDARDS Organisation.

I.e. it is a standard. Not for changing.

Exposure works in stops and arbitrarily changing one of the three variables in that equation would cause all sorts of merry hell and also mean that aperture and shutter speed settings become largely meaningless (form an exposure point of view).
 
Nawty said:
Err, because ISO stands for International STANDARDS Organisation.

I.e. it is a standard. Not for changing.

Exposure works in stops and arbitrarily changing one of the three variables in that equation would cause all sorts of merry hell and also mean that aperture and shutter speed settings become largely meaningless (form an exposure point of view).
Click to expand...

Yeah, I expected that (silly of me in the first place!), but how accurate are ISO's from one camera to another? Anyway, its probably not a difference of 2x is it? Two pics to follow though - ISO 100 appears better, surely of ISO 200 were to be the 'standard' it should appear better than the 100? Or is it always going to be dependent on the photo being taken?
 
IMGP7122.JPG


IMGP7123.JPG
 
There is some variability in real ISO, from memory DPReview tend to measure this (or at least they used to), from memory the highest variability I've seen is a real value of ISO160 when a camera was set on ISO100 but I could be making that up.

Anyway, the second of your pics looks mis-focussed which is why it's slightly blurry.

You won't see any difference in ISO100 and ISO200 shots if they are correctly exposed, the difference comes when you're shooting in RAW and trying to recover highlights.
 
these were both serious crops, taken from exactly the same point, possibly slightly oof, but no reason why it should be, I'll only tell upon taking numerous pics and deciding myself really!

thanks for all the input to all though, at least I have an idea why it defaults at ISO 200.
 
uberdude said:
these were both serious crops, taken from exactly the same point, possibly slightly oof, but no reason why it should be, I'll only tell upon taking numerous pics and deciding myself really!

thanks for all the input to all though, at least I have an idea why it defaults at ISO 200.
Click to expand...

Your comparison pics don't show what's going on. You need something with a lot of bright tones.

If you shoot a grey scale at ISO200 running from black to white, with the white end just on the correct side of blown, then in the next shot at the Lo setting it will have blown, and be unrecoverable. You lose one stop of highlight dynamic range.

Edit: that's why you can't use the expanded setting with highlight correction enabled.
 
Last edited:
HoppyUK said:
Edit: that's why you can't use the expanded setting with highlight correction enabled.
Click to expand...

Well you can, sort of...

If both are enabled then the lowest ISO you can go to is 200 (rather than 400 when highlight correction only is enabled) which sort of defeats the purpose of it! Although you can still use the higher expanded ISO's up to 12,800 if they are both enabled. (This is with my dads K-x so unless they've changed it massively for the K-r I suspect its the same)
 
Nawty said:
Err, because ISO stands for International STANDARDS Organisation.

I.e. it is a standard. Not for changing.

Exposure works in stops and arbitrarily changing one of the three variables in that equation would cause all sorts of merry hell and also mean that aperture and shutter speed settings become largely meaningless (form an exposure point of view).
Click to expand...

Its actually the International Organization for Standardization so ISO is not an acronym :D
 
Suvv said:
Its actually the International Organization for Standardization so ISO is not an acronym :D
Click to expand...

And amid strong competition, the May prize for 'Pedant Of The Month' goes too... :)
 
You must log in or register to reply here.
Back
Top