IQ180 with Phase One DF camera-colour issue

[cunim]

Jack, I still think there is something for Phase to investigate in the proportional red rise with underexposure. Certainly, all sats rise under those conditions but red rises more than green or blue. I see similar effects with low sun angles of course (different in Los Altos and Melbourne?). Not much to be done as flux dependent balance of the primaries is a fundamental sensor property. However, a red-reduce C1 style might be handy.

I don't have a quantum efficiency chart of the Dalsa chip but I would suspect its red response is extended relative to green/blue and to our eyes. So when all primary fluxes are low or when red light is prevalent (low sun eg), the camera sees more of it than we do visually. Wonder who has the chip response data?

 

[Dan Santoso]

Forgive me for off topic but

does your IQ comes with the plastic thingie that cover the cable release etc (below IQ180 sign). Mine does not and my dealer told me that Phase One sent the back without it.

Thanks

 

[Terry]

Forgive me for off topic but

does your IQ comes with the plastic thingie that cover the cable release etc (below IQ180 sign). Mine does not and my dealer told me that Phase One sent the back without it.

Thanks

Mine came with the rubber piece that covers it. My dealer is going to order replacements (as I know mine will be lost in short order) but the extras aren't available yet.

 

[kdphotography]

Forgive me for off topic but

does your IQ comes with the plastic thingie that cover the cable release etc (below IQ180 sign). Mine does not and my dealer told me that Phase One sent the back without it.

Thanks

Small self-sealing plastic door (lack of a better term) is on the front of the back below the lcd; A rectangular rubber gasket covers the side ports next to the CF card door. It's included. You should be able to get a replacement from your dealer...

ken

 

[Dan Santoso]

For some reason all IQ sent to my dealer does not have the rubber gasket.

what in the world!!!!

 

[tashley]

Like Terry says, you'll lose it in moments. Whenever I peel the top half off to stick the tech cam shutter sync thingie in, it is a bugger to get back in afterwards. I anticipate getting through a few of these.

 

[Guy Mancuso]

Geoff i got your file but what lens are you using here . Its marked 75mm. Phase does not have a 75mm lens unless it is the zoom

 

[Guy Mancuso]

Okay Geoff sent me a file but first you need to understand where the light is coming from which is directly overhead. Here is the problem the brick in the front is really in the shadows and you really can only go by the top of the bricks. Plus the color chart is on the shadow side. Plus you are .5 underexposed right out of the gate. So I boosted the exposure and only go by the top bricks as far as color because the bottom bricks are underexposed and in the next frame I boosted the shadow side.

Now going in and boosting the shadow side the bottom bricks are still under but not as bad. Honestly this is not a great file . Really the sun should be hitting the whole scene directly not from the top plus it is overcast which causes more saturation. I'm just not convinced given this file.

Boosted shadow

 

[Wayne Fox]

I see where you are coming from, but after shooting in red rock country all weekend, I'm seeing some red saturation issues, and I know it's not underexposure or shadows. Still seeing if I've got something in my workflow that might explain it. but if I want saturation to all colors, I'm having to pull the reds back down sometimes.

I'll work on in more and get back with you.

BTW, I understand about it being underexposed maybe contributing to this, but isn't this "new"? I don't recall issues like this with the p65+, and I know reichmann and dubovoy both mentioned some red issues.

 

[GeoffRoss]

Guy,

Sorry about the delay in responding, but I haven't had much time lately.

I can send to you an identically positioned Canon image of the same subject matter, and I can assure you the Canon doesn't have the same reds saturation problem, also being opened in Capture One using a generic Canon profile.

Anyway, I know there is a problem, and I have taken steps to solve it, by utilizing a modified camera profile. So as far as I am concerned I have done my best to alert others to it, and each person can make their own judgement. If you are happy with what you are seeing for your own images, then that's great, but I wasn't.

It is interesting that it appears that Wayne has also identified the same thing.

One other thing that occurred to me was that maybe others aren't viewing on a full gamut monitor. I use a top of the range Eizo, which pretty well covers the full Adobe RGB gamut. So it is possible that the issue isn't so obvious for others who have monitors with a more restricted colour gamut. It would explain it.

Regards,
Geoff Ross

 

[Dan Santoso]

I did a quick test via IQ LCD, did some bracket with red clothes, and I found the color in the LCD is darker/more saturated than the actual clothes even when I overexposed it.

I will check more in my PC later. This may be because of inaccurate LCD coloring.

During my last studio shoot, I notice that overexpose image gives washout color in the skin (LCD), while tethered the color looks nice in my monitor. I suspect the LCD's color is inaccurate.


Best,
Dan

 

[Shashin]

One other thing that occurred to me was that maybe others aren't viewing on a full gamut monitor. I use a top of the range Eizo, which pretty well covers the full Adobe RGB gamut. So it is possible that the issue isn't so obvious for others who have monitors with a more restricted colour gamut. It would explain it.

Regards,
Geoff Ross

Actually, it wouldn't. The relative difference would still be preserved in the conversion. As others have pointed out, there is certainly a contrast problem impacting your saturation.

 

[Guy Mancuso]

I'm on a Nec wide gamut monitor as well as Jack is

 

[Shashin]

Does anyone with this back have the facilities to do a proper color check? The testing here is too subjective to pin point the problem. At least a controlled environment would help.

 

[Jack]

Does anyone with this back have the facilities to do a proper color check? The testing here is too subjective to pin point the problem. At least a controlled environment would help.

Shooting a color checker and getting exact values is very difficult. That said, I have droppered the direct Sun crop of my Passport I showed earlier in this thread. If in C1 I use a linear response curve and flash profile, then adjust my grays to balanced by making slight adjustments to the levels slider and with saturation at 0, I am actually showing a slight R channel UNDER saturation in the reds and magentas, and a slight over saturation of R in the blues and cyans, with skin-tones being very close. But, we are talking really small amounts to begin with, so for my uses I have to say it is quite excellent as-is.

YMMV,

 

[goesbang]

Geoff, I shot some bricks with my IQ/C1 on the PC. Appears to me that there is no trace of red oversaturation at normal exposure, but that the proportion of red becomes nonlinearly higher with underexposure. The left image is slightly overexposed and looks very like the real thing. Slightly undersaturated if anything. The right image is underexposed by 2 stops and then raised in LR. Note the proportional increase in the red component. I would guess the QE of the chip is higher in the red and this is not being well compensated in C1. Just a guess.

What happens when you "raise" the exposure is that you steepen the curve. This raises contrast but also significantly increases saturation - in all colour channels. Just look what has happenned to your foliage.

 

[goesbang]

Just a thought.....
You guys who are having this red problem, what firmware version are you running?
The reason I ask is that the first time I shot with an IQ180 was when I did the demo for the global dealer launch here in Dubai. Those backs we used were pre-prod prototypes and weren't fully profiled. They had a terrible over saturation problem in the mid to three-quarter tone part of the red channel. The shadows were also slightly green.
My production back does not have this problem at all. We have had a firmware update since we received our backs, so I am curious to know if you are running older firmware. At the very least it would be good to remove that as one of the variables in this discussion. I am running version 1.19 from May26 2011.
For the record, my IQ180 is not showing any sign of this red over-saturation. Nor is my Aptus 12.
The accuracy in the Khaki/green area is also better than my P65+.
Cheers,

 

[GeoffRoss]

Hello all,

I am attaching two images taken a short time ago, and both within a couple of minutes of each other. Unfortunately it is still raining here, which affects the real colour judgement of things, but in this instance it is more a comparison of colourv rendering between a Canon image, and the Phase One image. Unless people have difficulty distinguishing colours, then I think this example will clearly show what I have been referring to. The images were both processed in Capture One and the only change has been the standard sharpening. The Phase One rendering of the bricks is certainly over-saturated. Even the Canon is more saturated than the actual bricks are.

I will leave it for you to make your own judgement.

Regards,
Geoff Ross

 

[GeoffRoss]

Try again! I Forgot to covert to SRGB, sorry.

Regards,
Geoff

 

[GeoffRoss]

and the Canon image