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IQ4 150 help working out how to get to a reliable histogram please.

vieri

Well-known member
Thank you Vieri, that is helpful! After testing various scenarios yesterday and today, that seems to work best for me as well. Generally speaking if I expose just to the left of center on the exposure bar and reduce an additional 1/3 stop it seems to be my sweet spot, I then confirm in the zone system and tweak if needed.
You are welcome Greg! What you describe here is pretty much what I do as well, until the histograms will be more consistently reliable :) I am old enough to have used film, both MF and FF, and working with external meters / camera meters is something I am very much used to, so it's not a problem to use the IQ4's meter rather than the - admittedly much fancier - live view histograms :) In the end, what counts for me is to have a replicable way to manage exposure and to know how my images will look like, exposure wise.

Best regards,

Vieri
 

ThdeDude

New member
Is it known whether, and if, to what degree the sensor of the Q3 100 and IQ4 150 are ISO invariant?

Assuming that the sensor is ISO invariant, i.e. doesn't matter whether ISO (camera gain) is increased or the gain in the RAW editor, there should no real advantage to exposure right up to the right edge of the histogram with the danger of losing any critical highlight details.

I am going back to my transparency days using my Pentax spotmeter to make a careful assessment what I would like to be zone 7 (texture), zone 8 (hint of texture), and zone 9 (no texture) in my final print, and expose accordingly (using base ISO). This approach would not use the histogram and the "exposure to the right" concept for determining the final exposure.

Any thoughts or suggestions?
 

onasj

Active member
Is it known whether, and if, to what degree the sensor of the Q3 100 and IQ4 150 are ISO invariant?

Assuming that the sensor is ISO invariant, i.e. doesn't matter whether ISO (camera gain) is increased or the gain in the RAW editor, there should no real advantage to exposure right up to the right edge of the histogram with the danger of losing any critical highlight details.

I am going back to my transparency days using my Pentax spotmeter to make a careful assessment what I would like to be zone 7 (texture), zone 8 (hint of texture), and zone 9 (no texture) in my final print, and expose accordingly (using base ISO). This approach would not use the histogram and the "exposure to the right" concept for determining the final exposure.

Any thoughts or suggestions?
Look here:

The IQ4-150 is not ISO invariant across all ISO values, but it is ISO invariant across local ranges. This is why I've learned to shoot at ISO 10000, 5000, 2500, 1250, 640, etc.—you get the most bang for your buck at these values.
 
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Reactions: med

ThdeDude

New member
Onasj,
Thanks for the link.
With "ISO invariant across local ranges" you mean when the graph is horizontal and you recommend to photograph at each end point ISO when the graph is horizontal.
For the IQ3 100, level only at ISO 50, 75, and 100, and then again at 3200 and 12800.
MN
 

onasj

Active member
Onasj,
Thanks for the link.
With "ISO invariant across local ranges" you mean when the graph is horizontal and you recommend to photograph at each end point ISO when the graph is horizontal.
For the IQ3 100, level only at ISO 50, 75, and 100, and then again at 3200 and 12800.
MN
Yes, meaning if you need ISO 6000 you are probably better off in terms of preserving DR if you shoot at ISO 5000 and push slightly in post than if you shoot at 6400.
 

med

Active member
I have not done any testing that is even remotely scientific, but based on my cursory testing with my IQ4 I seem to be getting vastly different exposure results than I was used to with my IQ250... I just did a quick forest walk and placing the highlights in the same general vicinity I did on my IQ250 histogram led to results that look about 1-2 stops under exposed when opened in C1. Something definitely seems amiss, and I will definitely need to do more testing before shooting anything critical.
 

algrove

Well-known member
Greg
I just skimmed the responses, but I have always had concerns that one channel when using ETTR can be blown out. So I always dial it back from ETTR like you did with your second histogram. To be frank at this point I have not used my IQ4150 for over a year now and forget what the histogram options might be, but I never bother with a jpeg histogram if a RAW histogram is offered. I have a very basic, small meter I often use to dial in my first exposure. Sekonic Twinmate L-208.
My histograms are also way off when comparing in camera and C1.
 

Greg Haag

Well-known member
Thanks for you insights Lou! I think I have found a workable solution for my upcoming trip. I am not sure what to make of my RAW histogram, it is so far off I don’t know how to make use of it. Unfortunately there is so little available information regarding the Phase One RAW histogram, at least that I can find.
 
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