Vincent, if you read the brief interaction between me and Alkibiades, you'll see where the confusion around colour casts arose. Alkibiades is saying you will get the colour cast with the Rodenstock 55 (as I did), but it's correctible. We all have different thresholds it seems. My threshold for colour cast is "Not visible -- nothing to correct". In contrast, Alkibiades' threshold seems to be "Can be corrected without damaging the image". It comes down to whether you think making LCC frames is a normal and unavoidable part of the workflow. If you're coming from the medium format back world, you'd consider it normal. I've only ever used mirrorless bodies, so for me it's normal -- which is why my threshold is where it is.Nice shots Steve! and thank you for the info.
This solution works good for you. But after looking a bit more into it, it looks like the movement will be quite limited with a 33x44mm sensor : about 7mm rise/fall, which is not much...
So I might give the Rodi 55mm a try in the end, hoping that I do not get the obvious color cast of Rob...
Anyway, one reason I like participating in these forums is I'm always learning things. Alkibiades suggest that one should use an LCC frame all the time with symmetrical lenses. I didn't think that was necessary, but I always like to check things empirically for myself rather than clinging to my assumptions. So yesterday I went for a little shoot in the snow with my Mamiya G 50/4, which is a symmetrical lens.
I made an LCC frame for every image, and in Lightroom I made with/without versions of each scene. Here's an image that used 9mm of rise at f/16. This is the correction frame. Note the light fall-off. I really can't see any colour shifts (which doesn't mean there aren't any!)
Here's the full image. On the left is the uncorrected version, and on the right is the version processed with Lightroom's Flat Field Correction tool using the LCC frame. Both are as imported, so no corrections for tone, temperature, etc.
Here's a 100% view of the top -- the region where I'd expect to see colour shifts. Again, on the left is uncorrected, and on the right is corrected using Flat Field Correction and the LCC frame. To my eye, there was no obvious magenta colour shift to correct (like what I saw on the Rodenstock 55). The Flat Field Correction tool also takes care of light falloff -- which it did here.
Here a 100% view of the top of the frame, this time using a gradient on both images where I brought highlights down considerably, and lowered exposure. Which blue sky is correct? That I cannot say. I find the blue of the sky in the uncorrected (left) version more pleasing, but it's not necessarily more accurate.
I should also mention that I shoot for black and white, and work almost exclusively in black and white, so you can see why I'm less fussed about colour faithfulness than other people! For this picture, I used the uncorrected RAF and darkened down the sky with a gradient (so any benefits from the Flat Field Correction fixing the light falloff would have been undone anyway).
So for what it's worth, I offer two conclusions:
1. The Mamiya G 50/4 is a very good lens. My current mounting approach only allows around 9mm of shift at this focus distance, but once I complete the conversion it should provide up to 15mm. Very preliminary testing suggests that the image quality will be plenty good at 15mm of shift, but that's to be confirmed.
2. I will not bother making LCC frames with this lens unless it's light falloff I want to correct. I'm simply not seeing any colour changes that need correction.