Grid pattern roblem with IQ180

[atwort]

Hi
I wanted to see if anyone else has the same problem with their IQ180.
I was testing the new back with my Linhof 679cs, 120mm schneider Apo Digitar and playing around with scheimpflug.
When the angle between the lens and 'film' plane was around 40 degrees I noticed some lines appearing on the image.
I did a Lens correction with the opal perspex, and I had a central cross pattern of 1 central vertical and another central horizontal line plus the expected color shifting. The lens correction software removed the color cast, but crucially not the defined grid pattern and I was left with what can roughly be described as 4 different mono tone rectangles placed together defined by the junction of the tonal differences at their edges.
Looking at the chip one can see identically shaped sensor panels, as if it is constructed from 4 pieces, and my guess is that the effect is caused by sensor pits adjacent to each other at these junction lines giving different readings that are not corrected by the algorithms.
I removed the IQ180 and did a test with my P45+ under identical conditions, no problem.
I have past all this on to my dealer in London and all relevant raw files.
Whilst this problem only became apparent to me under relatively high camera movements, it was not with a wide angle lens, and I am now waiting for my Linhof to come back from a small service, so I can test with either my 72mm or 47mm schneider Apo Digitars.
I suspect the problem my reoccur with these lenses at lower levels of camera movement.

Has anyone else noticed this.... Michael ?

[Doug Peterson]

Yes this is expected with an IQ180 with extreme movements or extreme angle lens designs (e.g. Schneider 28mm XL).

I'm somewhat surprised to hear of this with a Schneider 120mm. But a 40 degree tilt is a very large movement.

You can see this in our 28mm XL file in our publicly downloadable tests section:
  Phase One Digital Back Test Files

Lenses at the wide angle end like the Rodenstock 32mm HR which use a retrofocus design are preferable for this reason. At the macro end, again I'm a bit surprised to hear you ran into it, and I can only recommend you try slightly less extreme movements to get a sense for what your usable range will be.

Some improvements will likely be made over time with software/firmware to reduce this effect, or more to the point to extend the range of movements possible before this effect becomes detrimental. However it cannot be eliminated (i.e. at some extreme movement this effect will always be seen).

This is, simply put, one of the downsides of such a high resolution sensor. If your style of photography calls for frequent use of 40 degrees of tilt on a macro lens then this is likely not the right back for you. However, for most users we've found the benefits of the IQ180 far outweigh it's few downsides.

Just as reference this effect is also possible to produce on a P65+ and in theory on a P45+, but the movements/lens needed to do it are even more extreme. The P45+ I have never seen it in practical use and the 65+ only in some extreme ranges of movement combined with the widest lenses available.

One other quick point: the math done to produce the preview on the IQ display itself (the LCD on the back) does not include the same sophistication of math as the processing in Capture One (while it has a four-core processor in the back along with auxiliary processors it can't compare to a desktop processor so the math is simplified to keep the interface snappy fast). Therefore occasionally you will see this effect on the LCD but not in Capture One.

Doug Peterson (e-mail Me)
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[atwort]

Granted the camera movements were at the extreme to see the effect VERY clearly, but I think it is important to know at what point on which lenses this phenomena appears when doing work which does involve adjustment of the the plane of focus/ shift/ tilt/ and with unforgiving subjects like flat tone or gentle graduation.
I had no luck seeing your 28mm lens shot, can you send me direct link ?

[Mr. Rib]

I guess a P45+ is still the best back for architecture / for usage with a tech camera. What a good investment it was..

[Doug Peterson]

Granted the camera movements were at the extreme to see the effect VERY clearly, but I think it is important to know at what point on which lenses this phenomena appears when doing work which does involve adjustment of the the plane of focus/ shift/ tilt/ and with unforgiving subjects like flat tone or gentle graduation.
I had no luck seeing your 28mm lens shot, can you send me direct link ?

If you completed the form an email was also sent to your email address in case you somehow missed the link in the browser itself.

[EricWHiss]

I use a 90mm apo rodagon lens on a tilt device fit to my Rollei AFi-ii 12 quite a bit.   I am able to tilt the lens up to about 25-30 degrees.  The Aptus 12 is not the exact same thing as the IQ180 but share a very similar sensor or the same sensor.  So far this amount of tilt has not introduced the artifacts you describe at all and it seems it should be even less likely with the 120mm lens you are using.     Are you seeing the seams between the 4 quadrants or something else?  There's been a lot of discussion about these new 80mp backs that showed the seams under lens movements and it appears from some of the thread that a few IQ180 owners got their cameras serviced and had the problem go away.   I believe the sensor readout is done electronically by quadrant and each quadrant has its own electronics package to make things go faster but they then need to be calibrated to each other.   An easy way to test this out yourself is to shoot a very even toned surface such as a painted wall, 2 stops under exposed and then pull up the exposure in capture one.  Do this without any tilt or movements but using your 120.  Do you still see the pattern?

[atwort]

I am seeing visibly different results from each sensor quadrant, as if 4 different graduated tone rectangles were placed in a grid. Where they meet the tone change shows the join line.
I'm getting my Linhof back from service soon and will do some wide angle tests to repeat the effect under more critical neutral background test conditions.

I hope a service will sort this out, but I suspect it may be more complex.

[MNG]

Hi Atwort,

If you are using Capture 1 Pro V6 try updating to the latest software?

[Doug Peterson]

If you are using Capture 1 Pro V6 try updating to the latest software?

And with the latest firmware for the IQ.

[atwort]

I have done another test, this time with my 47mm apo-digitar,  virtually no lens movement but left and right horizontal stitching.
Wow, really heavy grid pattern with only 16mm shift to left or right. All the individual sensor sections clearly visible on the LCC opal exposure and the sensor basically useless for any meaningful professional work without having always to look and see if I'm getting 'gridding'. Hanging onto my P45+ thanks.
Phaseone have seen the requested RAW files and the back has been recalled.
It's a shame as the back gets such great reviews, but for this kind of money I don't see why one should have to now forget camera movements and stitching for fear of unusable results.
My conclusion is that this back is designed primarily for the Phaseone camera, field and technical cameras were not part of the design process.
If I get to test it's replacement and the problem is resolved I will gladly repost. I have always used Phaseone backs and they have been my professional work horses since going digital circa 2002.

[dchew]

That definitely does not sound right.  I have the 43xl with the IQ180 and it shifts 18mm without lines.  There are other image issues out at the edges when shifted beyond 15mm with the 43, but grid patterns is not one of them.  The 47 should be better.

Dave

[atwort]

I received a replacement IQ180 and ran the same tests and worse, I am glad to say the grid problem was not visible at all until an un useable amount of camera movement was applied.
So what I experienced before must have been a rogue back, still for the money you would think a thorough test before leaving the factory would be a good idea.

The biggest problem I now have is affording it !!!!