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07-02-2012, 08:32 PM   #1
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ISO 80 vs ISO 100

So is there a difference of between these on the Pentax K-5?

07-02-2012, 08:49 PM   #2
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Yes. Try them.
07-02-2012, 09:19 PM - 1 Like   #3
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more dynamic range with iso 80
07-02-2012, 10:51 PM   #4
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So why is ISO 80 off by default? And why do you have to enable the very high ISO's to get the lowest ISO available on the K5? I've always been curious as to why ISO 80 isn't on by default, is there a down side to it?

07-03-2012, 02:31 AM   #5
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QuoteOriginally posted by monk Quote
So why is ISO 80 off by default? And why do you have to enable the very high ISO's to get the lowest ISO available on the K5? I've always been curious as to why ISO 80 isn't on by default, is there a down side to it?
The only down side I can think of is the slower shutter speeds, i.e. the increased risk of blurry shots. However, the difference to ISO 100 shutter speeds is only minor.

I've noticed better DR at ISO 80 as well. Perhaps it's just not activated per default because of ISO 100 being regarded as the standard?

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07-03-2012, 05:29 AM   #6
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ISO 100 is the lowest the sensor goes by default so that means ISO 80 is not a default but an extended option, it's as simple as that.
07-03-2012, 06:00 AM   #7
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I've also read that 80 is not the native resolution of the sensor which makes 100 better.
07-03-2012, 06:21 AM   #8
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QuoteOriginally posted by Anvh Quote
ISO 100 is the lowest the sensor goes by default...
What does that mean?
Why is ISO 100 "the lowest the sensor goes by default", if ISO 80 truly expands dynamic range?

The K-5's ISO 80 setting does not limit dynamic range (like some fake ISO 50 settings on some Canon models), but increases it. So why is it not "the lowest the sensor goes by default"?

I did a quick search, found no explanation, and hence can only speculate that Pentax did not want to confuse users with a lowest setting that isn't a stop under the standard "ISO 100" setting. It would have led to a non-uniform response regarding adjusting other exposure parameters automatically when the user clicks through all ISO settings.

07-03-2012, 06:23 AM   #9
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QuoteOriginally posted by tabl10s Quote
I've also read that 80 is not the native resolution of the sensor which makes 100 better.
Not true. ISO 80 increases the dynamic range and his hence the (potentially) better setting.
07-03-2012, 07:21 AM   #10
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On the K-r, the default lowest ISO is 200, then you can have ISO 100 by activating extended ISO mode.
07-03-2012, 07:56 AM   #11
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QuoteOriginally posted by NickLarsson Quote
On the K-r, the default lowest ISO is 200, then you can have ISO 100 by activating extended ISO mode.
The same on my K-x. according to the manual, the only drawback of setting it at ISO100 is, "When the sensitivity is set to ISO 100, bright areas are more likely to occur."
If you use highlight correction which pegs the lowest ISO at 200, it "expands the dynamic range and the light level expressed by the CMOS sensor and prevents bright areas from occurring"
So if your'e an experienced photographer, you probably would know how to handle bright areas and shoot at the lowest ISO, but a hobbyist like me should probably stick to ISO 200 and highlight correction on
07-03-2012, 08:07 AM   #12
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QuoteOriginally posted by NickLarsson Quote
On the K-r, the default lowest ISO is 200, then you can have ISO 100 by activating extended ISO mode.
Indeed, this is similar to the fake ISO50 setting on some Canons as referred to by Class A, i.e. a reduction in dynamic range since exposing as ISO 50 is actually the same as overexposing ISO 100 and then lowering the exposure in post processing (without recuperating the additional blown highlights).

The ISO 80 setting on the K-5 is in a different league, since indeed it does increase dynamic range compared to ISO 100. So the result is not more blown highlights as in fake lower ISO but, on the contrary, fewer blown highlights.

My K-5 is always set to ISO 80 when I start shooting. And after having to use higher ISO I'll always dial down back to ISO 80 when light and anticipated image permits.

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07-03-2012, 08:42 AM   #13
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Thanks for clarifying this. I always assumed ISO 80 was like ISO 50 on Canon DSLRs (loss of performance). Looks like that's not the case.
07-03-2012, 09:15 AM   #14
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QuoteOriginally posted by Class A Quote
What does that mean?
Why is ISO 100 "the lowest the sensor goes by default", if ISO 80 truly expands dynamic range?

The K-5's ISO 80 setting does not limit dynamic range (like some fake ISO 50 settings on some Canon models), but increases it. So why is it not "the lowest the sensor goes by default"?

I did a quick search, found no explanation, and hence can only speculate that Pentax did not want to confuse users with a lowest setting that isn't a stop under the standard "ISO 100" setting. It would have led to a non-uniform response regarding adjusting other exposure parameters automatically when the user clicks through all ISO settings.
Sony the maker of the sensor makes them by standard from ISO100 to ISO1600, the upper limit i'm not sure off though. Anyway it's pentax doing that we have ISO80 not sony's and as such it's not a default the sensor comes with.

I've no idea why or how the DR is better with ISO80 then ISO100 since that shouldnt indeed be the case but the K5 is the only camera that offers ISO80 with this sensor, isnt that strange either?

The best explaination i can come up with is that pentax change the response curve maybe?
With test we see that Pentax DR is often starts lower and also ends lower then other brands so it seems pentax can influence that.
07-03-2012, 04:54 PM   #15
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QuoteOriginally posted by Anvh Quote
Sony the maker of the sensor makes them by standard from ISO100 to ISO1600, the upper limit i'm not sure off though.
ISO 1600 is indeed the upper limit (higher ISO settings are equivalent to digital pushing in post), but your statement "makes them by standard from ISO100" does not make sense.

QuoteOriginally posted by Anvh Quote
Anyway it's pentax doing that we have ISO80 not sony's and as such it's not a default the sensor comes with.
Have you considered the possibility that the sensor natively supports ISO 80 but that no one other than Pentax chose to exploit it?

I cannot imagine that Pentax has added some magic sauce to create an ISO 80 setting that the sensor does not natively support.

QuoteOriginally posted by Anvh Quote
I've no idea why or how the DR is better with ISO80 then ISO100 since that shouldnt indeed be the case...
No, it should be the case.

Only the lowest ISO setting achieves the optimal dynamic range. Any higher ISO setting reduces dynamic range because the full well capacity will be reached the sooner the higher the (ISO) multiplication factor. If you do not believe me, look at a dynamic range graph at DxOMark and see how DR loses a stop when you add a stop to the ISO setting.

QuoteOriginally posted by Anvh Quote
but the K5 is the only camera that offers ISO80 with this sensor, isnt that strange either?
It is as strange as the fact that ISO 80 is an extended setting on the K-5. You'll have to ask Pentax about the latter and other camera manufacturers why they didn't exploit the ISO 80 capabilities of the Sony sensor. Perhaps they didn't think the marginal increase in DR would be worth the effort of adapting the firmware.

QuoteOriginally posted by Anvh Quote
The best explaination i can come up with is that pentax change the response curve maybe?
The ISO 80 effect exists in RAW data as well, so special JPG tone curves cannot be responsible (they are used for the extended highlights mode).

DxOMark measured true ISO 80 performance. If Pentax had done some trickery, DxOMark would have exposed it.

QuoteOriginally posted by Anvh Quote
With test we see that Pentax DR is often starts lower and also ends lower then other brands so it seems pentax can influence that.
You can extend the highest ISO setting to your heart's content. For the Sony sensor in the K-5, ISO 1600 is the maximum value supported by the chip and Pentax just decided to allow more digital pushing than Nikon did with the D7000.

However, you cannot do the same at the low end. If you use tricks at the low end, they will not increase dynamic range and hence your trickery will be exposed.

To summarize, the Sony sensor must support ISO 80 natively. Why it is an "extended" ISO setting on the K-5 was the question by monk and I know that some explanations are wrong, but can only speculate about the true answer (see my earlier post).
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