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Author Topic: Lens Cast on a shift lens  (Read 7673 times)

cjmonty

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Lens Cast on a shift lens
« on: April 08, 2009, 01:29:59 pm »

Hey all,  I recently tried out the old 50mm Mamiya shift on my Phase Body and P45.  I love the lens, love the sharpness, love the versatility.

I hate the Red-to-Yellow-to-Green lens cast.
My pictures look like they had a run-in with the Bolivian Flag-  http://en.wikipedia.org/wiki/Flag_of_Bolivia

I thought this only afflicted extreme shifts with LF lenses...  

Can I correct for this with a white plastic disk?  Does anyone know about how to make a DIY lens cast calibrating disk for using in the field?
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Jack Flesher

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« Reply #1 on: April 08, 2009, 01:39:03 pm »

Quote from: cjmonty
Can I correct for this with a white plastic disk?  Does anyone know about how to make a DIY lens cast calibrating disk for using in the field?

Seems to plague any shift at certain times --- but yes, you can correct it with the disk.   Basic procedure is: Set up your image and shoot it, then stop down 2 stops using the shutter (you want to keep the aperture constant), cover the lens with the disk and take the white frame.  If you are in a hurry, forget the stopping down and just shoot a second shot with the disk over the lens as it seems to work just fine in most cases.
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cjmonty

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Lens Cast on a shift lens
« Reply #2 on: April 08, 2009, 02:40:10 pm »

Thanks!
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davidpz

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Lens Cast on a shift lens
« Reply #3 on: April 13, 2009, 08:04:46 am »

hi  presumably when you bought your p45 your received the white piece of perspex with it?

Anyway, to correct the lens caste & set up a LCC through capture one.

Set up your shot, put in the relevant movements/shifts, take a frame through the perspex ( you'll need to open up about 1>2 stops)
& now carry on shooting -without the pespex in front of the lens.
Download to yer computer & launch C1. Set up your white balance & on the blank grey frame go to 'create LCC'. Ping the eye dropper on this & when the s/ware has done its thing save the calibration (call it what you want - preferably something meaningful). You then apply this LCC to every frame that was taken with those movements/shifts on. You WILL need to take a new calibration frame each time you make any shift or tilt adjustments.

As far as I know you cannot create a LCC for a phase one back in anything other than Capture One. If anyone knows how to in P/Shop or Adobe Camera Raw, please let me know.

regards

Dpz

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BJNY

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« Reply #4 on: April 13, 2009, 11:05:10 am »

Do not open up your f-stop
but instead, lengthen your shutter speed

different f-stops have different falloff
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Guillermo

Tgrain

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« Reply #5 on: April 13, 2009, 11:25:30 am »

according to my phase one rep you should open up as much as possible (F-Stop) to get a good correction.
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tom_l

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« Reply #6 on: April 13, 2009, 12:33:29 pm »

as far as i know it doesn't matter if you change the shutter or the aperture to overexpose.
In a studio setup with a view camera(where shutter speed doesn't matter)  it is a pain to change the intensity of the strobes, I just open the aperture instead and results seem ok.



Tom
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AgencyDigital_NYC

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« Reply #7 on: April 13, 2009, 01:29:17 pm »

Quote from: davidpz
hi  presumably when you bought your p45 your received the white piece of perspex with it?

Anyway, to correct the lens caste & set up a LCC through capture one.

Set up your shot, put in the relevant movements/shifts, take a frame through the perspex ( you'll need to open up about 1>2 stops)
& now carry on shooting -without the pespex in front of the lens.
Download to yer computer & launch C1. Set up your white balance & on the blank grey frame go to 'create LCC'. Ping the eye dropper on this & when the s/ware has done its thing save the calibration (call it what you want - preferably something meaningful). You then apply this LCC to every frame that was taken with those movements/shifts on. You WILL need to take a new calibration frame each time you make any shift or tilt adjustments.

As far as I know you cannot create a LCC for a phase one back in anything other than Capture One. If anyone knows how to in P/Shop or Adobe Camera Raw, please let me know.

regards

Dpz

This is how you correct lens color shift.

tho_mas

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« Reply #8 on: April 13, 2009, 02:26:33 pm »

Quote from: davidpz
If anyone knows how to in P/Shop (...) please let me know
Process capture. Process LCC shot with the same settings (white balance, icc profile). Open capture in PS, add the LCC shot on a second layer. Invert second layer with the LCC shot and set layer mode to "overlay".

edit: sorry, forgot about the 50% grey... so...
1st layer: capture
2nd layer: create new, mode "overlay", select "fill with 50% grey"
3rd layer: LCC shot, set mode to color
4th layer: merge 2 and 3, invert, set to "overlay" and delete or turn off layer 2 +3

Without the 50% grey vignetting is corrected as well.
With the 50% grey just the color cast is corrected.
« Last Edit: April 13, 2009, 03:31:55 pm by tho_mas »
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davidpz

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Lens Cast on a shift lens
« Reply #9 on: April 14, 2009, 03:03:40 am »

Quote from: tho_mas
Process capture. Process LCC shot with the same settings (white balance, icc profile). Open capture in PS, add the LCC shot on a second layer. Invert second layer with the LCC shot and set layer mode to "overlay".

edit: sorry, forgot about the 50% grey... so...
1st layer: capture
2nd layer: create new, mode "overlay", select "fill with 50% grey"
3rd layer: LCC shot, set mode to color
4th layer: merge 2 and 3, invert, set to "overlay" and delete or turn off layer 2 +3

Without the 50% grey vignetting is corrected as well.
With the 50% grey just the color cast is corrected.

Thanks for this. I'll give it a try out as I'm getting more & more disillusioned with Capture 4 as each update is released & I'm not the only one reading the forum . My retoucher won't process through C4 & if we can get a workflow going through bridge/acr/pshop .... brilliant.
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CBarrett

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Lens Cast on a shift lens
« Reply #10 on: April 15, 2009, 07:19:35 pm »

Quote from: davidpz
Thanks for this. I'll give it a try out as I'm getting more & more disillusioned with Capture 4 as each update is released & I'm not the only one reading the forum . My retoucher won't process through C4 & if we can get a workflow going through bridge/acr/pshop .... brilliant.


FYI, if you're capturing in C1 Pro 4 but want to process in LR or PS... after you apply the LCC you can save as a DNG and have a Raw file that retains the LCC.  Might make things a little more efficient for the alternative workflow.

Personally, I have no probs with C1 4 now that I'm used to it...

-CB
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tho_mas

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« Reply #11 on: April 15, 2009, 07:37:18 pm »

Quote from: CBarrett
FYI, if you're capturing in C1 Pro 4 but want to process in LR or PS... after you apply the LCC you can save as a DNG and have a Raw file that retains the LCC.
Not here. DNG is created without any setting/adjustment. Am I missing something?
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ericstaud

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« Reply #12 on: April 15, 2009, 08:00:37 pm »

Quote from: tho_mas
Not here. DNG is created without any setting/adjustment. Am I missing something?

C1 Pro 4.7 writes the DNG with the color casts removed if you've used the LCC tool.  It's not a setting/adjustment that ends up as a processing instruction in the DNG, the color cast are removed altogether from the image.  There have been some bugs along the way where it was difficult to get the LCC to stick, but that was a few versions ago (and it could turn up when making DNG or RGB files.
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tho_mas

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« Reply #13 on: April 15, 2009, 08:11:25 pm »

Quote from: ericstaud
C1 Pro 4.7 writes the DNG with the color casts removed if you've used the LCC tool.  It's not a setting/adjustment that ends up as a processing instruction in the DNG, the color cast are removed altogether from the image.  There have been some bugs along the way where it was difficult to get the LCC to stick, but that was a few versions ago (and it could turn up when making DNG or RGB files.
Thanks, Eric! But I think I don't get it.
I use the LCC tool go to output and set output to DNG. Right?
But opening the DNG in ACR the color cast is back again...
« Last Edit: April 15, 2009, 08:22:07 pm by tho_mas »
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CBarrett

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Lens Cast on a shift lens
« Reply #14 on: April 15, 2009, 08:30:51 pm »

Quote from: tho_mas
Thanks, Eric! But I think I don't get it.
I use the LCC tool go to output and set output to DNG. Right?
But opening the DNG in ACR the color cast is back again...

Weird.  I haven't played with it in a while, but a while back the DNG would retain the LCC, though no other settings....
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tho_mas

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« Reply #15 on: April 15, 2009, 08:43:01 pm »

Quote from: CBarrett
Weird.  I haven't played with it in a while, but a while back the DNG would retain the LCC, though no other settings....
So maybe a bug. Maybe just here...?
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ericstaud

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« Reply #16 on: April 15, 2009, 10:27:53 pm »

Quote from: tho_mas
Thanks, Eric! But I think I don't get it.
I use the LCC tool go to output and set output to DNG. Right?
But opening the DNG in ACR the color cast is back again...


O.K., nevermind, I'm full of it.  Sorry to mislead you.  This worked on an earlier version of 4 just fine.  It's now NOT working on 4.7 for me on my intel laptop running 10.5.6.

Time to send an email to my dealer or to create a support case on the Phase One site.
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ericstaud

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« Reply #17 on: April 15, 2009, 10:32:44 pm »

Quote from: CBarrett
Weird.  I haven't played with it in a while, but a while back the DNG would retain the LCC, though no other settings....

Since the DNG is a RAW file, other converters won't read those settings anyway (except for maybe the "as shot" white balance from the camera).
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tho_mas

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« Reply #18 on: April 16, 2009, 04:38:55 am »

Quote from: ericstaud
Sorry to mislead you.  This worked on an earlier version of 4 just fine.
It's okay, no problem. I asked just out of curiosity as I don't need DNG at all.

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Mark_Tuttle

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« Reply #19 on: April 21, 2009, 12:43:05 pm »

Quote from: ericstaud
O.K., nevermind, I'm full of it.  Sorry to mislead you.  This worked on an earlier version of 4 just fine.  It's now NOT working on 4.7 for me on my intel laptop running 10.5.6.

Time to send an email to my dealer or to create a support case on the Phase One site.


You had me jumping for joy that one moment, but ....

Previous discussion on LCC and DNG
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Mark Tuttle
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