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01-15-2016, 06:59 AM   #1
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Is 200 the Native ISO for the 645D?

Is 200 the Native ISO for the 645D?
I had to go into the menu and pick extended sensitivity just to get the ISO setting below 400

01-15-2016, 09:24 AM   #2
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200-1000 native 100-1600 extended
01-15-2016, 09:35 AM   #3
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How do you set the ISO to 100 and is it a good idea to do so?
I have heard that cameras don't perform well below their native ISO, in other words, more is lost than gained
Thanks
01-15-2016, 09:51 AM   #4
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ISO 100 gives you more dynamic range, making it a bit easier to recover highlights and shadows.
I don't have a 645d but in my K-5 you can set extended sensitivity in the C menu.

01-15-2016, 11:32 AM   #5
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You expand the ISO range through the custom function menu, just like on the K-7 and K-5. There's really no reason not to, hence they've gotten rid of this setting in recent bodies.

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01-15-2016, 01:29 PM   #6
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I went into the custom menu and enabled Expanded Sensitivity and still cannot get a setting lower than ISO 200
01-15-2016, 01:46 PM   #7
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QuoteOriginally posted by D1N0 Quote
ISO 100 gives you more dynamic range, making it a bit easier to recover highlights and shadows.
I don't have a 645d but in my K-5 you can set extended sensitivity in the C menu.
What expanded Low ISO does is add +1 EV, so you aren't getting any real dynamic range over the Base ISO, you are just shifting it to the right. So you do get more shadow detail BUT at the expense of highlights. So you are at more risk of clipping.
01-15-2016, 03:10 PM   #8
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Here's the manual for it: http://www.ricoh-imaging.co.jp/english/support/man-pdf/645d.pdf

It says you can expand the sensitivity range in the C1 menu.

01-16-2016, 07:48 PM   #9
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cali92rs - I agree that extending the sensitivity below the base ISO does not lead to any gain in DR; indeed it would sacrifice highlights. However, I think the question here is what is the base ISO? Intuitively, one would think that the base ISO would be the bottom end of that which is normally made available (i.e. without using the extended ISO range). That would make sense! Except that I have seen conflicting reports about whether that is actually the case with the 645D. I can't remember where, but a few years back I remember reading that the firmware was heavily based on other cameras that did indeed have a base ISO of 200, which is why it worked that way, but that with the 645D the base is ISO100. Now, counterintuitive though that would be, it would make ISO100 the best to use from a DR and noise perspective.

So agree with your logic but not sure that the facts plugged into the logic are true :-)

Can anyone shed light on this, perhaps with a curve from test data?
01-16-2016, 07:58 PM   #10
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Ed:

FWIW, DxO indicates increased DR at ISO 100:

NB For some reason this link takes you to the wrong measurement, just scroll over to DR

Pentax 645D : Measurements - DxOMark

Last edited by Thomas; 01-16-2016 at 08:47 PM.
01-16-2016, 08:11 PM   #11
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Anybody out there know the 645D menus well enough to be able to hazard a guess as to why I cannot seem to get down to ISO 100 no matter what I try?
Obviously C,3 Expanded Sensitivity is where I have to go and I have that set to "ON"
But when I depress the ISO button and scroll the rear dial - the lowest setting that shows up in the top display is 200
I am open to any and all suggestions, this is a brand new camera from Adorama and I'm hoping this isn't some sort of malfunction
Thanks.
01-16-2016, 10:22 PM   #12
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QuoteOriginally posted by Thomas Quote
Ed:

FWIW, DxO indicates increased DR at ISO 100:

NB For some reason this link takes you to the wrong measurement, just scroll over to DR

Pentax 645D : Measurements - DxOMark
Thanks Thomas - that's the data I was referring to. It certainly seems to suggest that 100 is closer to base ISO than 200, otherwise it would lead to a reduction rather than an increase in DR.

---------- Post added 01-17-16 at 04:44 PM ----------

QuoteOriginally posted by uintaangler Quote
Anybody out there know the 645D menus well enough to be able to hazard a guess as to why I cannot seem to get down to ISO 100 no matter what I try?
Obviously C,3 Expanded Sensitivity is where I have to go and I have that set to "ON"
But when I depress the ISO button and scroll the rear dial - the lowest setting that shows up in the top display is 200
I am open to any and all suggestions, this is a brand new camera from Adorama and I'm hoping this isn't some sort of malfunction
Thanks.
Not sure (mine will go to ISO100) - have you got the latest firmware installed?

Latest 645D Firmware Update : Software Downloads | RICOH IMAGING

That should not explain it, as the function has worked since the first version of the firmware, but always good to exclude this possibility just in case something weird is going on.

Last edited by Ed Hurst; 01-16-2016 at 10:45 PM.
01-16-2016, 11:38 PM   #13
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QuoteOriginally posted by uintaangler Quote
Anybody out there know the 645D menus well enough to be able to hazard a guess as to why I cannot seem to get down to ISO 100 no matter what I try?
Obviously C,3 Expanded Sensitivity is where I have to go and I have that set to "ON"
But when I depress the ISO button and scroll the rear dial - the lowest setting that shows up in the top display is 200
I am open to any and all suggestions, this is a brand new camera from Adorama and I'm hoping this isn't some sort of malfunction
Thanks.
Turn off highlight recovery function? If that one is on, ISO 200 is the lowest you get.
01-17-2016, 01:26 AM   #14
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Something was niggling me; I knew there was a function that did that and couldn't think what it was. That is it precisely. I'll bet that fixes it :-)
01-17-2016, 01:13 PM   #15
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QuoteOriginally posted by Ed Hurst Quote
Something was niggling me; I knew there was a function that did that and couldn't think what it was. That is it precisely. I'll bet that fixes it :-)
Success!!!!

Thank you donesteban and Ed Hurst .

Bob
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