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P65+ High ISO Experience

Long-story short, I just purchased a used P65+ (doing the house flipping equivalent with Phase One backs, on my way to “IQ-something-full-frame”), and I would like to know where the “useable” ISO stops.

By “useable”, I mean low-light landscapes where I would need a 30-second to 1-minute exposure.

Thanks,

J.D.
 

dougpeterson

Workshop Member
Long-story short, I just purchased a used P65+ (doing the house flipping equivalent with Phase One backs, on my way to “IQ-something-full-frame”), and I would like to know where the “useable” ISO stops.

By “useable”, I mean low-light landscapes where I would need a 30-second to 1-minute exposure.

Thanks,

J.D.
That back features a Teledyne Dalsa sensor without Long Exposure mode.

It can do a reasonable mid-ISO exposure (ISO200)
It can do a reasonably mid-long exposure (e.g. 30 seconds)
It cannot do both simultaneously - at all.

That is you can do a 30-60 second exposure at ISO50. Or you can do a very short exposure (e.g. 1/250th) at ISO 200 or even ISO400 depending on your post processing and preferences. But you cannot do a 30-60 second exposure at ISO 200, or even anything close to it. Even a few seconds at mid ISO starts to push the limits of this back.

Hopefully your dealer shared some relevant raw files to you before you purchased so that this won't come as a disappointment.

One of the Dalsa sensors with Long Exposure mode (IQ2 60mp, IQ3 80mp) or one of the Kodak sensors would be a moderate improvement in this regard. One of the CMOS sensors (Credo 50, IQ1 50mp, IQ3 50mp, IQ1 100mp, IQ3 100mp) would be a large improvement in this regard.
 
Thanks Doug.

I did not buy the P65+ for long exposures in mind, my approach is ISO50 with typically nothing longer than 30-seconds. I asked mostly to "know" the limits, so as a result to know when to take my Nikon along where I know a "dark" scene will happen.

As always, you have the best info!

J.D.
 

dougpeterson

Workshop Member
I did not buy the P65+ for long exposures in mind.
Gotchya. It's a great back otherwise. I used it for weddings for a couple years; big sensor, great tonality, can even do ISO3200 in Sensor+ (I would generally convert files shot at that ISO to black and white and add contrast; grainy for sure, but pretty in their own right).

Best wishes with your new back. Welcome to Dante's.
 
CCD digital backs have highly inflated ISO numbers just like Fuji's cameras. Every now and then you would need to push the files in post-processing, which would make them look noisier.

Forget about the long exposure mode in the 60MP and 80MP Dalsa sensors (IQ260, IQ360 and IQ380) - they are very noisy and force you to shoot at ISO200 (while ISO140 is just an extended ISO for ISO 200).

For 30sec - 1min expousre, the 100MP CMOS and the 50MP CMOS are best (e.g. IQ3 100MP, IQ150 etc). For longer than 5min, the 50MP CMOS is the best because the 100MP would rely on darkframe NR to avoid red shadow issue (not sure about Hasselblad though).

If you shoot milky way landscape, then forget about medium format but instead get a Nikon D810A and a Sigma 14mm f/1.8 Art lens.
 

tcdeveau

Well-known member
"useable" ISO is pretty subjective and can vary depending on the intended use of the capture (web, print, etc) anyway, so I'd recommend doing some testing yourself when you get a chance. enjoy the new back!
 

Steve Hendrix

Well-known member
Thanks Doug.

I did not buy the P65+ for long exposures in mind, my approach is ISO50 with typically nothing longer than 30-seconds. I asked mostly to "know" the limits, so as a result to know when to take my Nikon along where I know a "dark" scene will happen.

As always, you have the best info!

J.D.

James

Keep in mind the ambient temperature will play a heavy role. I've recorded 90 second exposures with a P65+ that produced "usable" quality in 60º - 65º temps at ISO 50/100. Overexpose a bit if you can, it helps.

In my vernacular, usable means can the noise/grain be presented in such a way that if it is noticeable, it is not objectionable, and may even add some character, but also that details are still reasonably captured, rather than smudged or chunky. To this end, playing with the Noise reduction settings is a must in Capture One. With default settings, you may not see much noise at all, but you also will certainly be sacrificing detail, so I recommend sliding that luminance slider back to the left and see where your ratio preference of detail/noise is realized.

Motto: Don't give up detail without a fight!


Steve Hendrix/CI
 

Wayne Fox

Workshop Member
I would guess since the p65+ uses a CCD sensor, changing the ISO is mostly a metadata change, and basically affects the default processing of the image, but really doesn't change the data. That means noise characteristics are basically the same as underexposure. If you shoot at ISO 200, you could get the same results by shooting at ISO 50 and then pushing the exposure up 2 stops in Capture One. To me 3 stops underexpose gets pretty bordering on not acceptable, so 200 was the highest I would go when I was shooting that back.

Here's some links to a few images taken with an IQ180 at base ISO and at 200. It shows that pushing the exposure in post delivers pretty much an identical image.



This is a section of the two images at 100%, showing the noise really isn't any different ...



This image shows the histogram of the 35 iso shot before and after changing the exposure value in C1, notice how close it is to the image taken at ISO 200.

 
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Paul2660

Well-known member
Hi Wayne

I sincerely thank you for your post. It's still amazing to me how the general understanding of the CCD chip and iso settings. As you point out any setting beyond the base ISO is not handled the same way a CMOS chip where actual sensitivity can be stepped up on the chip. Basically the CCD is iso less. The only true way to push up iso is via sensor plus which bones make a huge difference albeit at loss of 3/4 resolution. Phase One also gave the P45+ an amazing long exposure capability but only at base ISO. I never felt that the IQ260 had anything near the same LE range as the P 45+

It's never been covered very well in any marketing literature from Phase One or Hasselblad both of whom seem to prefer to have the public continue to have the incorrect understanding that increasing the ISO on a CCD back is working the same as it does on a CMOS chip when instead it's only a metadata change.

Paul Caldwell
 
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