Luminous Landscape Forum
Site & Board Matters => About This Site => Topic started by: bjornaagedk on March 27, 2006, 12:55:53 pm
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Michael,
very interesting article. I have an equipment ”almost” like yours, - P45 back, Cambo Ultima 23 and Schneider Apo-Digitars. The Cambo Wide DS 35mm also.
I was expecting to read about you having problems with lens cast, because that’s what I have, shooting with P45 both in studio and on location.
As soon as I use tilt/shift functions with Cambo Ultima I see magenta/green colors, making the picture almost unusable without being corrected i C1 Pro with the LCC function.
When I use ´my Cambo Wide DS the I see lens cast even with the lens centered.
It seems like I am not the only P45 owner who has problems with LC, according to several threads about this subject.
How about you? No problem??
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Not sure what you mean by "problem". It's the nature of the beast. With very wide lenses and when using movements a lens cast frame needs to be shot.
I use an Expodisk rather than the plastic card provided by Phase. Works much better and more quickly.
Michael
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Not sure what you mean by "problem". It's the nature of the beast. With very wide lenses and when using movements a lens cast frame needs to be shot.
I use an Expodisk rather than the plastic card provided by Phase. Works much better and more quickly.
Michael
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OK. Maybe it is me, but I don't like that I have to shoot an extra image every time I change camera movements. I do this 15-20 times every day in the studio, and is takes me a lot of time.
B
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OK. Maybe it is me, but I don't like that I have to shoot an extra image every time I change camera movements. I do this 15-20 times every day in the studio, and is takes me a lot of time.
B
[a href=\"index.php?act=findpost&pid=61149\"][{POST_SNAPBACK}][/a]
are there examples of the level of cast?
i do a lot of shift stitches. if you shift left, expose (once with the expo), middle then shift left, expose (once with the expo).. are the color cast between the three and exposures identical after the software gets through with them? or do you need curves to match them
jim
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What you can do is spend a couple of hours building a library of cast files. Just shoot a series with increments of about 3 degress of rise or shift on each axis, for each lens, and label them appropriately.
A lot of work, I know, but then you never have to do them again.
Michae
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i do a lot of shift stitches. if you shift left, expose (once with the expo), middle then shift left, expose (once with the expo).. are the color cast between the three and exposures identical after the software gets through with them? or do you need curves to match them
jim
[a href=\"index.php?act=findpost&pid=61151\"][{POST_SNAPBACK}][/a]
Do you have to use masks when you shift stitch with the Canon 1DsMk2 and the Canon Tilt-shift lenses ?
Alain
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Do you have to use masks when you shift stitch with the Canon 1DsMk2 and the Canon Tilt-shift lenses ?
Alain
[a href=\"index.php?act=findpost&pid=61154\"][{POST_SNAPBACK}][/a]
no.. they pretty much match exactly, exposure and cast (ensuring you use manual exposure)
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no.. they pretty much match exactly, exposure and cast (ensuring you use manual exposure)
[a href=\"index.php?act=findpost&pid=61155\"][{POST_SNAPBACK}][/a]
That's nice. I have to try it since I have the 1DsMk2 and the 24TS. I need to get the 45TS or 90TS as well. Do you use all 3 lenses or have a favorite?
Alain
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That's nice. I have to try it since I have the 1DsMk2 and the 24TS. I need to get the 45TS or 90TS as well. Do you use all 3 lenses or have a favorite?
Alain
[a href=\"index.php?act=findpost&pid=61156\"][{POST_SNAPBACK}][/a]
i do 90% of my work with the 90T/S. it's the sharpest as well. I used to use the 45 as well, but picked up a mamiya 50mm shift lens, which is much sharper than the Canon 45 T/S (also cheaper.. you can find them for $4-500)
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What you can do is spend a couple of hours building a library of cast files. Just shoot a series with increments of about 3 degress of rise or shift on each axis, for each lens, and label them appropriately.
A lot of work, I know, but then you never have to do them again.
Michae
[a href=\"index.php?act=findpost&pid=61153\"][{POST_SNAPBACK}][/a]
Michael: What about lens tilts -- do they impart a color-cast, or is it only lens shifts that cause it?
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Only shifts, unless the tilts are significant.
Michael
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The "problem" is that you just bought a camera that unpredictably casts unwanted color in different parts of your images. You then have to figure out a way to take this color out, either in C1, or Photoshop, or both. This does not only happen with wide angles or movement, but in my experience, it happens with all lenses and in all conditions.
How effective is C1 in dealing with this? Reasonably, but only if you take a LCC shot for every set of captures with a particular lens and in a particular setting. Changes in lighting conditions or elevation in my experience will lead to partial removal of the cast by C1. A standardized library of LCC shots will not, in my view, satisfy a stickler for image quality.
I ran the following test with my 250SA CFE: I took a shot of snow at 1000m. I then went down to 450m and took another shot of snow in the same lighting conditions and an LCC reference shot. When I applied the reading to the shot taken at 1000m, it only partially removed the cast. And this is a telephoto lens on a Hassy 503 -- no wide anlge on an LF camera!
The "problem" is that Phase One does not prepare you for this. The issue of lens cast is treated under the heading "large format photography" in their manual. It is given thin treatment. The manual states that lens cast is "very rare" in lenses longer than 60mm. It also does not state with any clarity at all that lens cast correction would require an LCC reading for every set of captures.
Would you buy a camera knowing in advance that it degrades your images, no matter how well you could reverse the degradation through added workflow steps? The answer would perhaps differ for every customer, but the manufacturer needs to acknowledge that this is a problem and be completely forthright with its customers about it.
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What specifically is causing the color shift?
I was under the impression it was the aperture-grille IR filter (pinkish metallic looking that rainbows as you turn it at an angle). I also understand the color IR filter (blue-cyan) does not cause this?
IF my assumption above is correct, then it would seem a relatively simple fix for Phase to deal with... So I suppose there is more to it?
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The "problem" is that you just bought a camera that unpredictably casts unwanted color in different parts of your images. You then have to figure out a way to take this color out, either in C1, or Photoshop, or both. This does not only happen with wide angles or movement, but in my experience, it happens with all lenses and in all conditions.
How effective is C1 in dealing with this? Reasonably, but only if you take a LCC shot for every set of captures with a particular lens and in a particular setting. Changes in lighting conditions or elevation in my experience will lead to partial removal of the cast by C1. A standardized library of LCC shots will not, in my view, satisfy a stickler for image quality.
I ran the following test with my 250SA CFE: I took a shot of snow at 1000m. I then went down to 450m and took another shot of snow in the same lighting conditions and an LCC reference shot. When I applied the reading to the shot taken at 1000m, it only partially removed the cast. And this is a telephoto lens on a Hassy 503 -- no wide anlge on an LF camera!
The "problem" is that Phase One does not prepare you for this. The issue of lens cast is treated under the heading "large format photography" in their manual. It is given thin treatment. The manual states that lens cast is "very rare" in lenses longer than 60mm. It also does not state with any clarity at all that lens cast correction would require an LCC reading for every set of captures.
Would you buy a camera knowing in advance that it degrades your images, no matter how well you could reverse the degradation through added workflow steps? The answer would perhaps differ for every customer, but the manufacturer needs to acknowledge that this is a problem and be completely forthright with its customers about it.
[a href=\"index.php?act=findpost&pid=61199\"][{POST_SNAPBACK}][/a]
Just my words. I think it is a big problem. If it is the "nature of the beast" I think it is a very bad nature of a 30.000$ back.
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Just my words. I think it is a big problem. If it is the "nature of the beast" I think it is a very bad nature of a 30.000$ back.
[a href=\"index.php?act=findpost&pid=61207\"][{POST_SNAPBACK}][/a]
any chance someone can post a full jpg of one of the discolored shots from off axis?
jim
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any chance someone can post a full jpg of one of the discolored shots from off axis?
jim
[a href=\"index.php?act=findpost&pid=61215\"][{POST_SNAPBACK}][/a]
And while we're at it, how about the corresponding white frame image? ...
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I for one would just like to see more shots from the trip! Especially the forest shots...
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Having never heard of lens cast before coming across this thread, I find the subject quite fascinating. I too would like to see examples of the phenomena and learn more about it.
If anyone could elaborate on the cause of lens cast and the process of dealing with it or point me to more information on it I'd be appreciative.
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A pretty comprehensive overview can be found at:
http://support.phaseone.com/KBFiles/1557/1/LCCMac.pdf (http://support.phaseone.com/KBFiles/1557/1/LCCMac.pdf)
Mark
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Here is a typical example using a Hasselblad ArcBody with Rodenstock Apo-Grandagon 45mm
The degree and position of the green/magenta shift varies from lens to lens
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Here is an LCC exposure for this lens
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Just to clarify,the test images above were captured using a P25 and not the P45
and,FWIW,I am not an owner of either back,yet
Mark
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This alone (not to mention the cost) would ruin a P back for me. Never saw this on my Kodak Pro Back.
4x5 film doesn't have these issues.
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Here's a before/after example of LCC being applied to a P25 file
The Before
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And After
Apart from shooting the exposure in the field the application of the LCC correction from
within Capture One takes only a couple of seconds per image
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Doug,
The color cast also gives me a knot in the stomach but,in practice,the correction routine
takes a mere seconds.
What also makes me cautious is that the corrections can only be applied from within CaptureOne
and as a result one is then tied to that software to process images the could be seen
as color cast challenged.
Workflow aside,I find i like the results I've been getting processing P25 files through ACR
better than what I get in CapOne and i'm certain i'm in the VAST minority with that view.
I still find that CapOne files apply a little too much smoothing for my taste for some images
that results in a subtle 'watercolor' effect in some areas of fine detail-like distant trees and
foliage,etc. ACR results might be ever so slightly 'grainier' is sky areas but the clarity of
fine details at a distance are more in line with what I expect from a 'large format' capture.
Mark
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Only shifts, unless the tilts are significant.
Michael
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In my work with 4x5 I just about use tilts only, and most of the time movements are relatively minor. The only instance I use shifts is when I want to keep a vertical... vertical, which is rare. Totem Pole in Mt Valley is one of the very few instances I recall where shifts were necessary. Very tall and very close, if you shoot from within the Sand Dunes at the base of the Totem Pole. I don't even use tilts with Spiderock since it is quite a ways from the rim of Canyon de Chelly and down below the horizon.
In many instances with landscapes minor distortions due to tilting the camera upwards are unnoticeable because there are no straight vertical lines. However, trees are one notable exception. So, when I want to shoot trees and keep them perfectly vertical, I use a telephoto because it allows me to stand further back and shoot level.
All this to say that the color cast would'nt be a problem for me if I used the P45 (which I may...). Seems like all this is a lot of ado about nothing, unless you use shifts regularly (when photographing architecture for example).
Alain
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Only shifts, unless the tilts are significant.
Michael
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All this to say that the color cast would'nt be a problem for me if I used the P45 (which I may...). Seems like all this is a lot of ado about nothing, unless you use shifts regularly (when photographing architecture for example).
Alain
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yes.. for normal landscapes, i pretty much just use tilts as well... but i also do urban and industrial landscapes, and this is the area i'm concerned with.
jim
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Mark:
Thanks for posting these examples and the link!
A couple of questions:
1) Approximately how much rise or shift was being used in the posted images? It appears as though it may have been very little in both images, unless it was an extreme shift and not rise/fall.
2) Have you noticed this effect with tilts? In the Phase link you provided they indicated it is also a problem with tilts in some lenses.
3) Lastly, how effective is the software at completely removing the shift, and does it destruct the image or image detail in any other way? (I ask because on my monitor it appears the "corrected" image still has some residual color issues in the affected central area. Is this just a function of the web jpeg-ing or can you see it in the original file?)
Thanks!
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Alain
The two images I posted were unshifted,untilted captures and clearly show the cast.
I have only very limited experience with the P45 but I would assume it behaves in
a very similar way with wide angle lenses as does the P25
I have also gotten colorcast on P25 files using Hasselblad V series lenses 50 (obvious)
and 80mm (subtle) and the SWC-M with 38 biogon (severe) so camera movement is not
the only criteria one needs to be aware of.
Leaf Aptus22 files using the identical lenses shows no colorcast whatsoever.
Unfortunately, Leaf has traditionally had noise issues with long exposure times where
Phase excels.
Eight to ten seconds seems to be the cutoff point for Leaf files in my tests but newer back
files (A75) seem to be significantly improved.
Mark
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Alain
The notion that color cast is present only with extreme wides and/or movements is simply incorrect. It is present in all of my images, regardless of the lighting situation or which lens I use. My second worst lens in this regard (after the 24mm digitar) is the 250 SA CFE. I have now changed 3 backs and the problem persists.
In light of this, would you still say this is much ado about nothing?
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The two images I posted were unshifted,untilted captures and clearly show the cast.
[a href=\"index.php?act=findpost&pid=61289\"][{POST_SNAPBACK}][/a]
OUCH!!! That does not sound good at all... Perhaps the new Aptus 75 is worth consideration...
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On the subject of rise/shift in landscape images: I often use rise/fall in landscapes instead of tilting the entire camera, but then it's easy to impart rise and shifts on my camera... Each to their own method...
FWIW, I do agree that the perspective distortions are not detectable with most landscape images due to no regular parallel lines (forests full of trees excepted), but the resulting image taken both ways will often look different. Not that one is worse than the other, just that the difference can be seen
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It is present in all of my images, regardless of the lighting situation or which lens I use. [a href=\"index.php?act=findpost&pid=61290\"][{POST_SNAPBACK}][/a]
Boghb: Was yours with a P25 or P45?
Michael: Did you see any color shift in un-shifted images with your P45?
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Jack,
In my experience (and again i want to state that I am not a phase back owner and am
basing my observations on only a few hundred files) Capture One has eliminated the
color cast to my COMPLETE satisfaction and any residual color shift that might be seen
on the reference images i posted is not present in the original 16bit file.
Mark
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Wouldn't the Aptus 75 have the same problem? I am slso curious why the 1Ds2 doesn't have this same problem.
Leaf has some nice sample raw files. Mostly of pretty feathered birds though if you know what I mean. Apart from the subject matter I found them to be pretty amazing and requiring very little post processing.
http://www.leafamerica.com/products/products_aptus75.asp (http://www.leafamerica.com/products/products_aptus75.asp)
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Jack,
Capture One has eliminated the
color cast to my COMPLETE satisfaction
[a href=\"index.php?act=findpost&pid=61294\"][{POST_SNAPBACK}][/a]
Thanks for the clarification Mark!
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Wouldn't the Aptus 75 have the same problem? I am slso curious why the 1Ds2 doesn't have this same problem.
Leaf has some nice sample raw files. Mostly of pretty feathered birds though if you know what I mean. Apart from the subject matter I found them to be pretty amazing and requiring very little post processing.
http://www.leafamerica.com/products/products_aptus75.asp (http://www.leafamerica.com/products/products_aptus75.asp)
[a href=\"index.php?act=findpost&pid=61295\"][{POST_SNAPBACK}][/a]
I have seen and worked with Aptus 22mp files created with a Hasselblad H2 and they are free of any color shifts whatsoever. No more post-processing needed than with a 1DsMk2 file. Very sharp images too.
Alain
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Jack, I have the p45. I had the p25 before that, but I never noticed lens cast with it.
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Jack, I have the p45. I had the p25 before that, but I never noticed lens cast with it.
[a href=\"index.php?act=findpost&pid=61312\"][{POST_SNAPBACK}][/a]
Thanks for that clarification Boghb, but I really did not want to hear this...
FWIW I recently saw some files from a friend's P45/Hassy H lenses and have to say I was extremely impressed! But for my uses I really need to be able to use whatever back I get on a view camera with movements and I don't like the idea of doing the white frame for every image, shifted, tilted or not... It sounds like I'll need to take a harder look at the Aptus 75.
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The Hassy 39 backs might also be worth checking out, although the Phase problem appears to be a Kodak problem...
I have been considering a DB for some time as well, but there is no way I would be getting into individual image calibration... certainly not after spending this kind of money!
I am looking forward to MR's analysis of this.
Regards,
Bernard
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Thanks for posting the images and info.
Another question: Are the images able to be calibrated in any version of the C1 software or only in the DB specific version?
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The problem is called "vigneting" and is a product of the cosine 4th law. Certainly not new and it does happen with film. Has anyone tried a center filter?
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Daniel
As far as I know the LCC calibration option is available in all versions of C1 pro
I don't have C1 lite so someone else will have to confirm that it is available.
That having been said any purchased back will come with the appropriate software.
Mark
P.S. Anon E. ,the color cast does not manifest itself in a geometric fashion (i.e. it doesn't appear
equidistant from the center) so a center filter should not be effective.
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The problem is called "vigneting" and is a product of the cosine 4th law. Certainly not new and it does happen with film. Has anyone tried a center filter?
[a href=\"index.php?act=findpost&pid=61327\"][{POST_SNAPBACK}][/a]
As far as I know light fall off doesn't introduce any color casts on film, it results in a mere darkening of the frame as one comes closer to the corners.
On view cameras I typically don't bother using a center filter for lenses 110 mm or longer.
Vignetting is different from light fall off in that it is provoked by a mechanical obstruction preventing the entry of the light (possible causes being a filter that is too thick or a lens shade for instance).
Regards,
Bernard
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As far as I know light fall off doesn't introduce any color casts on film, it results in a mere darkening of the frame as one comes closer to the corners.
On view cameras I typically don't bother using a center filter for lenses 110 mm or longer.
Vignetting is different from light fall off in that it is provoked by a mechanical obstruction preventing the entry of the light (possible causes being a filter that is too thick or a lens shade for instance).
Regards,
Bernard
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Vignetting and light fall off are one and the same thing. Vignetting can be a natual condition of light as in the case of the cosine 4th law or it can be caused by a menchanical obstruction of the lens barrel. And this does shift color. I would try a 55mm lens with 4x5 film if you want to see the effect clearly.
Digital camera can be programmed to a certain degree to counter this effect as it is predictable. Or, as others have done, it can be fixed later.
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P.S. Anon E. ,the color cast does not manifest itself in a geometric fashion (i.e. it doesn't appear
equidistant from the center) so a center filter should not be effective.
[a href=\"index.php?act=findpost&pid=61330\"][{POST_SNAPBACK}][/a]
The examples you give show a classic case of vignetting so I don't see why a center filter will not help. Have you tried a center filter?
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The examples you give show a classic case of vignetting so I don't see why a center filter will not help. Have you tried a center filter?
Both examples were shot with the Hasselblad ArcBody using the Apo Grandagon 45mm
There is a dedicated center filter for this lens and it was used in both cases.
Sorry. Theory and practice don't always intersect
Mark
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Both examples were shot with the Hasselblad ArcBody using the Apo Grandagon 45mm
There is a dedicated center filter for this lens and it was used in both cases.
Sorry. Theory and practice don't always intersect
Mark
[a href=\"index.php?act=findpost&pid=61343\"][{POST_SNAPBACK}][/a]
What does it look like without the center filter?
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Vignetting and light fall off are one and the same thing. Vignetting can be a natual condition of light as in the case of the cosine 4th law or it can be caused by a menchanical obstruction of the lens barrel. And this does shift color. I would try a 55mm lens with 4x5 film if you want to see the effect clearly.
[a href=\"index.php?act=findpost&pid=61340\"][{POST_SNAPBACK}][/a]
Interesting, I haven't noticed any color shift when using my Schneider 58 mm XL on 4*5. But I do indeed typically use a dedicated center filter with that lens.
Would mind sharing with us the physics underlying the appearance of a color shift?
Regards,
Bernard
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Interesting, I haven't noticed any color shift when using my Schneider 58 mm XL on 4*5. But I do indeed typically use a dedicated center filter with that lens.
Would mind sharing with us the physics underlying the appearance of a color shift?
Regards,
Bernard
[a href=\"index.php?act=findpost&pid=61349\"][{POST_SNAPBACK}][/a]
I use a 55m Grandagon on a 6x12 camera and when I don't use a center filter there is a color shift - usually to blue. I am not sure there is a whole lot of research on this, but my educated guess says it seems to be because of underexposure - variations in exposure cause color shifts. There is most likey a transmission problem with the film because the incoming light is at such an oblique angle and the blue layer for color film is at the top. Film is also most sensitive to blue. The underexposure emphasizes this problem. (I use a 1.5 stop neutral density center filter and it almost completely eliminates the problem.)
In mark's case, he seems to be getting a green/magenta shift. The bayer pattern is mostly green. If the pixels are not physically flat, this may be giving the green shift toward the edge. The white balance may be trying to compensate so there is a magenta shift toward the center. The reason his dedicated center filter may not be working is the surface of the CCD causes a greater fall-off effect (this is why I asked him the difference with the filter off). Phase One in their instruction recognize the problems of the cosine 4th law (that is the reason for natural vignetting), but have decided to invent a new term called "lens cast."
But why not the Canon DSLR? Short focal length lenses are a reverse telephoto design so they can be far enough away from the CCD to allow the mirror to rise. So at a comparable angle of view, you are not actually getting light hitting the CCD at a similar angle of incidence as you would from a veiw camera. Also since the effect is predictable, DSLR manufacturers can compensate electronically to a certain degree - most DSLRs know what lens is attached. In fact lens data is stored in the exif file. Not something that can be done with the view cameras or Hasselblad Arc Bodies.
So it appears the cosine 4th law works. When using wide angle lenses, the term "vignetting" is applied. So far in this thread I have not seen anything new that would suggest another cause, but I am game if someone can come up with another explination.
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Have a look:
Image Data:
Phase One P45 back on a Cambo Ultima 23 with slide back
Lens: Schneider ApoDigitar 120mm/5,6 Macro
Light: 1 Lightbox placed apx. 1m above object.
Images taken at 1/125 sec. f/11
JPG's: (4 posts)
Straight: All camera levels in center position / no shift/tilt.
Shift20mm: Lens shifted 20mm down
Tilt10: Lens tilted 10 dgr.
Lcc: Lens Cast Correction added, based on Shift20
This is what I call "the problem".
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Shift 20mm
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Tilt10
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Shift20 w. LCC added in Capture1 Pro
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Never shot the ArcBody and 45mm combo WITHOUT the center filter so I can't offer
any images under that scenario to act as a sort of 'control'.
Mark
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Daniel
As far as I know the LCC calibration option is available in all versions of C1 pro
I don't have C1 lite so someone else will have to confirm that it is available.
That having been said any purchased back will come with the appropriate software.
Mark
[a href=\"index.php?act=findpost&pid=61330\"][{POST_SNAPBACK}][/a]
True, but I do post production work and I was just curious if the correction was available to standard versions of C1 in case I ever get a client sending me color-casted images. It wouldn't be very cost-effective to buy a P25 just to process a few raw files!
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Daniel
I've had C1 pro for Mac installed for close to two years now and have installed the
incremental upgrades along the way at no cost. I've been using it for an assortment of
Canon digital cameras
Without owning a Phase back I am able to process P25 and P45 files and apply LCC
corrections where needed so it seems pretty clear that one doesn't have to buy a back
to access the proper C1 software.
Assuming you have a version of C1 go to the White/Color Balance tab and in the upper
left hand corner under ICC profile info you will see the Lens CC window.
It will be greyed out for files other than Phase files but at least you can see if you have
access to it should you need it.When C1 detects a phase file there will be,in this window,a
list of any LCC calibration files you have saved and can apply where neccessary
Mark
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I've used various Leaf Valeo backs for the last few years on a Cambo 5x4 with Digitar lenses out to 28mm and I've never seen anything like that either.
I know you're all saying it's easy enough to correct but it would still really anoy me. Explaining to clients on location or art directors in the studio why the images they are seeing raw out of the camera look so lousey is not something I would expect from kit of this sort of cost.
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I've used various Leaf Valeo backs for the last few years on a Cambo 5x4 with Digitar lenses out to 28mm and I've never seen anything like that either.
I know you're all saying it's easy enough to correct but it would still really anoy me. Explaining to clients on location or art directors in the studio why the images they are seeing raw out of the camera look so lousey is not something I would expect from kit of this sort of cost.
[a href=\"index.php?act=findpost&pid=61419\"][{POST_SNAPBACK}][/a]
I have now a Leaf Aptus 75 here in my studio for testing, comparing to my PhaseOne P45 back.
These images are exactly the same camera position, just switched from P45 back to Leaf back.
The P45 image is in a version with LCC applied also.
What do you say?
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Bjorn,
Being on a slow connection now I couldn't get the samples.
What do you see?
Cheers,
Bernard
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There is definitely a cast in the P45 image not present in the Leaf image.
I brought the images into PS so the effect can be more easily seen. I set a neutral point in Levels for each back by selecting a point to the left of the "EF" text. Than I matched the luminosity between the two backs using curves (again sampling the same point) and cranked up the saturation.
Attached is the result for anyone is interested (resized for web viewing).
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When C1 detects a phase file there will be,in this window,a
list of any LCC calibration files you have saved and can apply where neccessary
Mark
[a href=\"index.php?act=findpost&pid=61390\"][{POST_SNAPBACK}][/a]
LCC files are specific to the lens, back and the shift/tilt settings. Without the lens and the back it is not possible for anyone else to correct the colour shifts unless the back owner supplied a set of LLC files with the P45 captures. Better to correct the files before delivery methinks...
It is my understanding that the colour shifts are a trade off between colour fidelity and resolution in the lens design. The Schneider Digitars exhibit this shift as reported, but are way sharper that normal glass such as Hasselblad. The P45 surpasses the res of most other lenses and thus on a 'normal' camera only generates more pixels, not more detail. MR alludes to this in his write-up and I have seen it for myself.
However, I have not used normal LF lenses (my Schneiders, Fujinons and Rodenstocks) on the P45 since the Horseman camera, that I used for my own article a few weeks ago on LL, needs dedicated lens mounts. I cannot say if the back is the culprit or the lenses, I am just passing on what I was told by the Phase One guys.
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Nick
This is a good point. It is probably why I get more cast with my 250SA CFE than my wider MF lenses. The Superachromats are highly color corrected and sharper than most other MF lenses. They are also uncoated.
With the Superachromats and the 24mm Digitar on the Horseman, I feel I need to take a LCC reference shot every time I move the camera. Otherwise I am not satisfied that the cast is completely removed. Do you agree (at least with respect to the Digitar)?
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The Dalsa chip is supposed to be better at avoiding colour shifts. Something to do with the depth of the wells in which the photosites sit.
Quentin
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This color shift effect is not the same as vignetting. It is a real and annoying problem. I had it with my Kodak SLR/c. It is to do with the sensor design.
Experience seems to point to this being a bigger problem with the larger resolution chips. The problem is usually worse with wide angle lenses where the light rays are at a steeper angle of incidence to the sensor plane.
From various sources I have assembled the following summary.
Aptus 22 - No problems of this kind
Phase One P25 - Some problems of this kind compensated with Capture 1 and LCC shots
Phase One P45 - More extreme version of P25
Aptus 75 - Some problems reported with Wide angle lenses (eg: Schneider 35XL) but only at shifts of 20mm +
People differ about whether this is a problem for them or not. For me it is a potential problem.
I would like to go down the Aptus 75 route. My worry is that there may be subtle issues with wides with non extreme shift angles. These issues might only emerge when photographing, say, a minimalist white interior... but then it would necessitate more work in post.
I notice that the Rodenstock Sironar Digital 35 has a wider image circle, and longer flange focal length than the Schneider 35XL. Perhaps it will suffer less than the Schneider 35XL when used with the Aptus 75 as the angle of incidence of the light rays will be lesser than with the Schneider. However... all this is making me quite concerned as it is virtually impossible to test all the options prior to purchase. I have no information about the distortion or other characteristics of the Rodenstock lens and dealers do not typically stock them. In addition, the exotic platform I would need to mount the 35 on means that the lens I would like to test needs a weird and wonderful mount!
My gut feel is that we are still at the bleeding edge, where purchasing decisions might need to be reversed at significant cost if errors are made.
The lack of standardisation in the camera platform area is a real minefield. For example. I can buy a sliding adapter for my Cambo Ultima. But it only allows switching between portrait and landscape format if I buy an H1 fitting digital back...
However, I already posess a full suite of Mamiya lenses, and do not want to have to replace the Mamiya with Hassleblad gear.
So far I can't find a way of using MFDB for my work without buying at least one (and possible two) new camera platforms. (I already possess two view camera, one MF and Canon SLR platforms, so I am running out of glass cabinet space!)
Add this to issues like this color cast... and I am finding the process of getting into MF digital extremely complicated and error prone.
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I recently had the opportunity to test a Phase p45 back side by side with a Leaf Aptus 75 in my studio.
My setup: Camera: Cambo Ultima 23 view camera, Lens: Schneider Apo-Digitar 120mm/5,6 Macro, Light: 1 strobe softbox apx. 1m above subject.
See the test images with 20mm shift and make your own conclusion!
http://homepage.mac.com/reklamefoto/FileSharing19.html (http://homepage.mac.com/reklamefoto/FileSharing19.html)
The P45 images are processed in C1Pro software without LCC.
The Leaf images are processed in Leaf Capture 10.
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I recently had the opportunity to test a Phase p45 back side by side with a Leaf Aptus 75 in my studio.
My setup: Camera: Cambo Ultima 23 view camera, Lens: Schneider Apo-Digitar 120mm/5,6 Macro, Light: 1 strobe softbox apx. 1m above subject.
See the test images with 20mm shift and make your own conclusion!
http://homepage.mac.com/reklamefoto/FileSharing19.html (http://homepage.mac.com/reklamefoto/FileSharing19.html)
The P45 images are processed in C1Pro software without LCC.
The Leaf images are processed in Leaf Capture 10.
[a href=\"index.php?act=findpost&pid=62796\"][{POST_SNAPBACK}][/a]
Great test! Pretty well sums up the issue on color-cast!
I do however have a question on ultimate resolution -- How does ultra-fine detail compare between the two backs? I ask because dealing with the color-cast may be worth the hassel if the P45 delivers significantly better resolution.
Thanks!
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Is there any reason why the test frame >P45_shift20mm+LCC.tif< appears
overall green AFTER the LCC correction has been applied ?
I'm not a fan of the LCC routine and,as such,will more likely consider the A75,but from
my experience using a properly done LCC file results in an almost perfectly corrected image
which this frame clearly is not.
Mark
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Is there any reason why the test frame >P45_shift20mm+LCC.tif< appears
overall green AFTER the LCC correction has been applied ?
I'm not a fan of the LCC routine and,as such,will more likely consider the A75,but from
my experience using a properly done LCC file results in an almost perfectly corrected image
which this frame clearly is not.
Mark
[a href=\"index.php?act=findpost&pid=62850\"][{POST_SNAPBACK}][/a]
Mark: I don't think he actually applied the correction to image shown, but rather just posted the correction file so folks could see what it looked like.
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The Leaf backs have other problems that the Phase backs do not have. Lousy software for one and it's Mac only for now.
Dave Gallagher at Capture Integration in Atlanta told me they have decided to no longer sell Leaf due to problems with the software, overheating and crashing problems.
So beware if you are considering a Leaf. The lens cast issue may be minor in perspective.
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I've not had any problems with the leaf software at all. I know it's not the best capture/process software package available but it's always worked well within its spec for me.
As for overheating, that may be an issue that exists with integrated screens but my Valeo is often on for very long periods of time and I've never had any problems with it.
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Mark: I don't think he actually applied the correction to image shown, but rather just posted the correction file so folks could see what it looked like.
Jack
I'm not so sure. The frame that I mentioned (P45_Shift20mm+LCC.tif) is accompanied
be a line of red text that states "Lens Cast Correction added in C1 Pro". Seems to indicate that
this frame has had the correction applied.
Mark
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The Leaf backs have other problems that the Phase backs do not have. Lousy software for one and it's Mac only for now.
Doug,
Have you used the Leaf software to arrive at this conclusion?
By almost all accounts,firsthand by me and secondhand by others, v10 from Leaf is as
problem free as anyone elses.
Previous versions were problematic,admittedly,but a lot of bad press that now circulates is based
on references in old postings sourced from different forums.
v10 is certainly not as all encompassing as C1 but,then again,it's free and while the native
software is Mac only Leaf files are supported by a host of other Raw converters including
Adobe Camera Raw and Raw Developer.
Mark
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Jack
I'm not so sure. The frame that I mentioned (P45_Shift20mm+LCC.tif) is accompanied
be a line of red text that states "Lens Cast Correction added in C1 Pro". Seems to indicate that
this frame has had the correction applied.
Mark
[a href=\"index.php?act=findpost&pid=62931\"][{POST_SNAPBACK}][/a]
I have just processed the images in C1Pro again to clear things up.
1) Gray balance set in "center" - file, WhiBal card. The settings transfered to the other images.
2) 4 new RGB images processed.
B