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10-16-2018, 07:55 PM   #1
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645D ISO range

I received my 645D yesterday, and messing around with the settings, I noticed that the native range is 400-1000, and with the custom function on, I can access 200-1600. This doesn't seem to align with the spec sheet low of 100. I'm on the firmware v1.33.

Is this normal? Are there any benefits besides reducing light between the expanded 100 and native 200?


Last edited by asamimasa; 10-16-2018 at 08:06 PM.
10-16-2018, 08:12 PM   #2
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You probably have highlight correction on- this will double the effective minimum ISO. Disabling it should enable access to ISO 100, as long as you also have the expanded ISO range custom function enabled.

If you ask me, gating ISO ranges behind an "expanded" setting is a bad idea. There's a reason this was discontinued in favor of allowing the full range by default on newer cameras

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10-16-2018, 08:21 PM   #3
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Never mind, figured it out. Highlight corrections were on, putting me at 200 base. It's been a while since I used anything CCD

Question still stands, is ISO 100 desirable over 200 on this camera? Is 100 pulled or the actual native low ISO?

oops, didn't refresh. Thanks for the quick reply Adam.

Last edited by asamimasa; 10-16-2018 at 08:29 PM.
10-18-2018, 11:35 PM   #4
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QuoteOriginally posted by asamimasa Quote
Never mind, figured it out. Highlight corrections were on, putting me at 200 base. It's been a while since I used anything CCD

Question still stands, is ISO 100 desirable over 200 on this camera? Is 100 pulled or the actual native low ISO?

oops, didn't refresh. Thanks for the quick reply Adam.
I'll gladly read some opinions about the bolded text, although the most missed thing from my old K-5 was their 80 ISO (I'm a full-open-shooter).

10-19-2018, 04:24 AM   #5
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I don't know the specifics about the 645D sensor, but there were reviews for the K-5 suggesting highlight compensation gave a bit more dynamic range - I set it on the camera and haven't switched it off so my lowest ISO is 160.

For the 645D, I shoot it at ISO 200 (expanded ISO & highlight compensation set for a similar reason - although I haven't tested the difference. I've seen some discussions as to what the 645D base ISO really is (100 or 200), however there's a reason why Pentax set the default minimum ISO to 200. Pentax are better judges than I to explore the advantages or otherwise (at least until I have time/inclination to test it).
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