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Author Topic: Lenscast with T/S lenses and Phase backs  (Read 3349 times)
pss
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« on: October 11, 2006, 02:03:39 PM »
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i am thinking of getting a T/S lens (55mmPQ) for my rollei 6008...i have a Phase back P20...i have never had to correct any of my pics for lens cast...will i have to shoot a plastic card before every shot? i want to use this hand held, shooting people, so i don't think the plastic card is a realistic solution for this kind of shooting...i also want to use it for stitching, so i guess i would have to shoot 2 different cards (one for each exposure)?
i have read through several threads here about lenscast and extreme wide angle lenses with alpas,...obviously the 55 won't allow these extreme movements and the 55 is also not really wide...
does anyone who uses the hartblei have problems?
this issue seems a little random, some people see it in every shot, some never....i have never seen any shift oof any kind with the 40mm (my widest lens)...any input welcome...thanks
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ericstaud
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« Reply #1 on: October 11, 2006, 03:29:18 PM »
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You need to understand what the term "retrofocus" means.  The alpa lenses (non-retrofocus) are a large format design.  A 35mm large format lens actually sits 35mm from the film plane when focused at infinity (the rear element is even closer than that).  On your camera all the lenses sit 80-100mm from the film plane.  They only achieve focus because of their retrofocus design.  The retrofocus design allows you to have a mirror box between the film and lens so that you can look through the camera between shots.  As a general rule you will not have LCC issues with retrofocus lenses (i.e.: cameras with mirror boxes), because the light it hitting the sensor more or less straight on.

That said, I use a Fuji GX680 with a H25.  When using swings, tilts, and shifts there are subtle lens casts.  Most often very subtle.  It is usually magenta.  If I miss the cast in the shot and don't shoot a calibration card, then a quick trip to photoshop to reduce magenta in the Hue/Sat tool does the trick.  This only works if there is nothing else magenta in my shot of course.  In many pictures you might never notice the cast.  If you shoot your model on a white cove, the cast would show up more easily.  If you're out in a forest it would likely be too subtle to tell.

Of course the best thing would be to test out your back/camera with the lens you are considering.  I have no experience with the P20 or the Rollei.

I am working with the Fuji right now.  180mm lens.  The lens is about 7" from the sensor of the H25.  The lens is tilted forward slightly and shifted down 10mm.  The uncalibrated shot has about 4 points of magenta in the upper right hand corner.  It does not show up on the yellow fabric I am shooting on.  This is pretty typical of the H25 GX680 combo I use.

[attachment=1033:attachment]
« Last Edit: October 11, 2006, 03:32:19 PM by ericstaud » Logged
pss
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« Reply #2 on: October 11, 2006, 05:02:24 PM »
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thanks for the reply...i actually saw the magenta on the right hand side (all along the side)...i am assuming you have some movements with this shot? i guess the only way to find out is to get the lens on the camera and see how bad it is....i have read that some people make LCC profiles for several positions (some 100s) and apply them accordingly...so a setting for a often used movement could be applied even if the actual movement was 1mm less/more? the effect would be a lot less noticeable?
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ericstaud
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« Reply #3 on: October 11, 2006, 05:53:20 PM »
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We're all Beta testers now.

If you want to to create a new look, you could also try applying the correction to shots that don't need it.  You could also make a correction off a shot of a tie-dye shirt.  Or defocus a shot and use that as the correction capture.

Good luck with the tesing.  Let us know what comes of it.

-Eric
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mkravit
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« Reply #4 on: October 11, 2006, 06:54:56 PM »
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Quote
i am thinking of getting a T/S lens (55mmPQ) for my rollei 6008...i have a Phase back P20...i have never had to correct any of my pics for lens cast...will i have to shoot a plastic card before every shot? i want to use this hand held, shooting people, so i don't think the plastic card is a realistic solution for this kind of shooting...i also want to use it for stitching, so i guess i would have to shoot 2 different cards (one for each exposure)?
i have read through several threads here about lenscast and extreme wide angle lenses with alpas,...obviously the 55 won't allow these extreme movements and the 55 is also not really wide...
does anyone who uses the hartblei have problems?
this issue seems a little random, some people see it in every shot, some never....i have never seen any shift oof any kind with the 40mm (my widest lens)...any input welcome...thanks
[a href=\"index.php?act=findpost&pid=79975\"][{POST_SNAPBACK}][/a]

I have used the P20 on a Rollei 6008AF using the Schnider 40 I had color cast issues.

I also tested a P25 on a Hasselblad Flexbody with a Zeiss 40 CF and also got color cast issues.

Shoot a white seamless and see if you have it or not.
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pss
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« Reply #5 on: October 11, 2006, 06:58:04 PM »
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thanks eric, not trying to create a look....only the clean look....
and since my 14n days, magenta and cyan are not my favorite colors....
only camera i wish i had never sold is the 680....i used to shoot that handheld....do you have the 65? do you have any LCC problems with that one? when using movements?
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pss
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« Reply #6 on: October 11, 2006, 07:10:40 PM »
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Quote
I have used the P20 on a Rollei 6008AF using the Schnider 40 I had color cast issues.

I also tested a P25 on a Hasselblad Flexbody with a Zeiss 40 CF and also got color cast issues.

Shoot a white seamless and see if you have it or not.
[a href=\"index.php?act=findpost&pid=80015\"][{POST_SNAPBACK}][/a]

i have the zeiss 40mm...no colorcast at all!
on a fixed (non T/S) lens it should not be a problem anyway....shoot the plexi at different f-stops and apply accordingly later on (if needed)...
when shooting people it is just not really possible to hold the card out before every shot....
i really can't believe that there seems to be no logic to this problem...some people get it, others don't, some lenses have it, some don't...i understand that there are circumstances where it is more likely to happen or even unavoidable, but a P20 with a 40 should either have it or not...not some have it, some don't...does not make any sense, the manufacturing standards should be to high for that....
i have shot with the 40 in the studio on white or light grey background many times and never saw anything...
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pss
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« Reply #7 on: October 14, 2006, 11:06:49 AM »
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ok..i had a chance to put the 55 T/S on my camera yesterday....i have absolutely 0 colorcast, nothing at all....did some shots of a white wall tethered with max movements...nothing at all...just wanted to let everybody know....
probably won't go with it because of the limited movements and the fact that there is no swing (unless you rotate the camera of course)...all in all i think the X-ActII is the better way to go (a lot more options for about the same money)...
i am starting to wonder if lenscast is also back dependend (meaning variations between a P25 and a P25)...considering that some people get lenscast without movements on fixed lenses and i don't even get them with movements....i guess i will know more when i see a digitar on the X-Act!
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ericstaud
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« Reply #8 on: October 14, 2006, 03:53:11 PM »
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That sounds like a positive test regarding your P25.  

The X-Act II looks like a very cool camera.  Like almost all camera gear I have interest in these days, I wish there was more information published on the net.  I saw an X-Act II adapter for Alpa a few months ago on ebay.  I could not find any info on what it was.  Maybe you could put Alpa lenses on the act II???  Who knows.  Are you using the X-Act II for the people shooting?

I tend to use the longer lenses on the GX680 so I can't remember/comment on if there was LCC with the 65 on this particular P25.  My sense is that with this particular combo of 680 and P25 there is no relationship between the focal length of the lenses and the ammount of LCC.  It doesn't happen without tilt/shift though.

Let us know what you end up with.

-Eric
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pss
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« Reply #9 on: October 14, 2006, 04:16:39 PM »
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eric, i am planning to use the X-ActII for people shooting as well as fun/private landscape stuff and maybe some architectural...like i said i used to shoot with the 680 handheld using movements and that was a wild affair...sweaty and with mostly unpredictable results...but definitley worth it...shooting with the 55 on the rollei would be similar, but i find the movements a little limiting (especially for stitching) and because of the digital crop it is really hard to focus when the movements are in place....so i think if i am tripod bound anyway, might as well go with the X-Act...it uses all 6000 lenses, backs, finders along with all 4x5 lenses...because i have the P20, there is plenty of coverage left on my lenses for movements and obviously the digitars would give me even more room....
the other reason to go with the X-Act is to let me use my longer lenses with it....it will probably be a while before i get one, but i will keep you updated...
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