DPReview.com is closing April 10th - Find out more

What does ISO have to do with HDR PQ or C-Log?

Started 1 month ago | Questions thread
MarshallG
MarshallG Veteran Member • Posts: 8,951
Re: What does ISO have to do with HDR PQ or C-Log?

Brian Greenstone wrote:

I'm hoping someone can explain this to me, but I'm totally confused about the relationship between ISO and dynamic range. When shooting in CLog3 you're supposed to use ISO 800, and when shooting HDR PQ you're supposed to use ISO 400. I have no idea why, or why shooting at ISO 200 will reduce my dynamic range. Those things seem to be entirely unrelated to me as I've always assumed ISO to just be a signal amplifier to boost what's coming from the sensor. But I don't see how that has anything to do with the number of stops of dynamic range that can be captured in those various HDR/Log formats. If anything I'd think a higher ISO would give me *less* dynamic range since it might cause the signal from the sensor to clip. I don't get it.

Can someone please clarify this for me? Also, I read somewhere that the ISO needs to be in multiples of 4 for best results. Ergo, ISO 400 or ISO 1600. ISO 800 or ISO 3600. What's up with that too?

I think the reason is that CLOG 3 is an expanded dynamic range.  What that means is that, from a midpoint, there are more stops of gray above and below that mid-point. If you shoot ISO 100, you can’t get enough stops of gray on the high end, so you need a reduced exposure.

 MarshallG's gear list:MarshallG's gear list
Canon EOS R5 Canon EF 50mm F1.4 USM Canon EF 85mm F1.8 USM Canon EF 16-35mm F2.8L II USM Canon Extender EF 1.4x II +4 more
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow