Ad
Ad
Ad
Pages: [1]   Bottom of Page
Print
Author Topic: colorcast and Alpa  (Read 1929 times)
alifatemi
Full Member
***
Offline Offline

Posts: 171



WWW
« on: October 12, 2013, 12:04:26 PM »
ReplyReply

Hi, I like to know about color cast problem on ALPA camera. I am considering buying Alpa TC with PhaseONe back but am worried about this problem. Thanks.
Logged

Ali
pixjohn
Sr. Member
****
Offline Offline

Posts: 671


« Reply #1 on: October 12, 2013, 12:31:33 PM »
ReplyReply

The camera body has nothing to do with color cast. It's created with the digital back and lens combination. The good news, it's very easy to fix with the phase 1 software. I shoot a lens calibration on every shot and apply it to the images.
Logged
alifatemi
Full Member
***
Offline Offline

Posts: 171



WWW
« Reply #2 on: October 12, 2013, 01:19:32 PM »
ReplyReply

The camera body has nothing to do with color cast. It's created with the digital back and lens combination. The good news, it's very easy to fix with the phase 1 software. I shoot a lens calibration on every shot and apply it to the images.

so for every shoot we need a shoot calibration!? is it for just wide angels or all lenses?
Logged

Ali
ErikKaffehr
Sr. Member
****
Offline Offline

Posts: 7333


WWW
« Reply #3 on: October 12, 2013, 02:37:03 PM »
ReplyReply

Hi,

You can reduce/eliminate the problem by using retrofocus designs. Symmetric, Biogon type, lenses have most problems and this is related to geometry. Wide angles, symmetric design and digital sensors is no great combination.

Hint, modern Rodenstock wideangles are often retrofocus designs, so are all Distagons.

Best regards
Erik


so for every shoot we need a shoot calibration!? is it for just wide angels or all lenses?
Logged

Paul2660
Sr. Member
****
Offline Offline

Posts: 1713


WWW
« Reply #4 on: October 12, 2013, 02:56:55 PM »
ReplyReply

It's vey dependent on your back.  40mp or less and colorcast issues will not be as bad, light fall will be the same.  LCC corrects for both light fall off and colorcast. 

With a 60MP or higher the retro focus designs from Rodenstock will help on light fall off and a bit on colorcast.  23HR 28HR 32HW and 40HW.  The Schneiders will be much harder to correct and will need a physical center filter even up to 60mm.  Rodenstock only makes center filters for the 23 28 and 32mm.

It has nothing to do with Alpa as Arca and Cambo will all have the same issues with various lenses. 

You will need to shoot several LCC shots throughout the day depending on the light available.  Shifts will also require a separate LCC.  LLCs are just part of the workflow. 

Paul Caldwell
Logged

Paul Caldwell
Little Rock, Arkansas U.S.
Photography > http://photosofarkansas.com
Blog> http://paulcaldwellphotography.com
alifatemi
Full Member
***
Offline Offline

Posts: 171



WWW
« Reply #5 on: October 12, 2013, 09:29:35 PM »
ReplyReply

Can I use also LR to correct colorcast by shooting LCC or only CaptureOne?
Logged

Ali
Wayne Fox
Sr. Member
****
Offline Offline

Posts: 2827



WWW
« Reply #6 on: October 12, 2013, 10:11:58 PM »
ReplyReply

Using a tech camera without any tilt or shift and retro focus lenses reduces apparent lens cast, even with my Rodenstock 40 it isn't too severe. (IQ180 back which I believe exhibits the most problems).  If you shoot a lens cast calibration shot with almost any lens you can see some LC and light falloff, even for reflex design cameras.  I have found that often with my rodenstock 40, 70, and 150 there is no obvious issue on the image, although with the 40 there is enough going on it's better to correct it (I also usually correct on the 70 as well).  The 150 I don't worry much about it since the problem really isn't color cast but just some light falloff (lunless I've shifted it).

You shoot the calibration shot each time you change anything (focus, shift/tilt, f/stop).  However, as an example the difference between one taken at f/11 and f/16 is pretty much imperceptible. I have a full set of pre shot calibrations that I can use when I forget, and even though they aren't perfect (focus may have been different, they are all shot at 11 and maybe the shot I'm correcting is not), they work fine.  I'm really bad about remembering to shoot one, but I manage pretty well, never really lost a shot because of it.

LR does not perform LCC corrections but handles vignetting pretty good for the 150 and even the 70.
Logged

alifatemi
Full Member
***
Offline Offline

Posts: 171



WWW
« Reply #7 on: October 13, 2013, 12:06:52 AM »
ReplyReply

Can we reach the same picture quality of Alpa combination but with own PhaseOne body using  mirror up? I am about to shift to MF but this colorcast, I am not happy with it although am so much fall in love with combination of Alpa TC and those small superb high quality lenses! It seems they are not practical for me. (and not to mention I hate phaseone body and those big auto focus lenses!)what a controversy: you love something but can't use it, you hate something but its more practical for you!
Logged

Ali
BartvanderWolf
Sr. Member
****
Offline Offline

Posts: 3585


« Reply #8 on: October 13, 2013, 05:34:41 AM »
ReplyReply

Can I use also LR to correct colorcast by shooting LCC or only CaptureOne?

Hi,

You can use the Adobe DNG Flat Field plug-in for Lightroom for the correction of light fall-off and color cast.

Cheers,
Bart
Logged
Paul2660
Sr. Member
****
Offline Offline

Posts: 1713


WWW
« Reply #9 on: October 13, 2013, 08:18:37 AM »
ReplyReply

Personally i feel , if you are going to look at 60-80mm and beyond then you will have excellent results with a Phase One DF+ body and Phase One LS or Mamiya lenses.  I like the DF and had hoped to see a more aggressive upgrade price to the DF+ from Phase One, as they did on the AFDIII  to DF, but it did not happen this round. 

I switched to the tech camera solution for the wides, 28, to 60mm.  I don't think that there is a good solution with either Phase One lenses or Mamiya that gets the same sharpness corner to corner.  Plus the addition of tilt with the wides gives an impressive increase in DOF in many shooting situations. 

Alpa, Cambo and Arca are all using the same lenses, so if you have picked the Alpa platform, I would try to find a dealer that will let you shoot both, a DF+ with wides and the Alpa. 

The Phase One body will not have any color cast issues on a 60MP 80MP sensor and you won't need to shoot the LCC, but once you get used to the workflow the results are worth it.  Actually weight of body and lenses is about the same the tech camera taking up a bit more bulk.

Wayne makes a great point about creating a library of LCC's for future use as in the thick of it I also sometimes forget to shoot them.   I find you need to have an LCC from a similar lighting situation to get it to work but so far I not found a limit to how many LCC's that Capture One allows you to keep.

Bart's point about the plug in for LR is a good one also.  I tired this briefly when it first came out and did not like the work flow, preferring the way Capture One handles it. 

Paul Caldwell
Logged

Paul Caldwell
Little Rock, Arkansas U.S.
Photography > http://photosofarkansas.com
Blog> http://paulcaldwellphotography.com
MikeJackson
Newbie
*
Offline Offline

Posts: 8


« Reply #10 on: October 29, 2013, 06:38:39 PM »
ReplyReply

Hi,
Having recently purchased a used Alpa 12 SWA/Leaf Aptus 22 back, complete with Schneider 47mm XL Apo-Digitar, I would like to add a lens in the region of 70-90mm.  Ideally, I would prefer not to mess around with profiling and won't usually be using any shift movement.  I have my eye on a Schneider Alpa Apo-Helvetar 75mm f/5.6 or standard Apo-Digitar 72mm f/5.6 and would appreciate any comments, and/or sensible alternatives,(again without profiling).
Many thanks in anticipation.
Logged
dchew
Sr. Member
****
Offline Offline

Posts: 563



WWW
« Reply #11 on: October 29, 2013, 07:31:55 PM »
ReplyReply

Hi,
Having recently purchased a used Alpa 12 SWA/Leaf Aptus 22 back, complete with Schneider 47mm XL Apo-Digitar, I would like to add a lens in the region of 70-90mm.  Ideally, I would prefer not to mess around with profiling and won't usually be using any shift movement.  I have my eye on a Schneider Alpa Apo-Helvetar 75mm f/5.6 or standard Apo-Digitar 72mm f/5.6 and would appreciate any comments, and/or sensible alternatives,(again without profiling).
Many thanks in anticipation.

The Alpa AH 75 and AD 72 are the same lens.  Schneider calls it a 72, but if you check out the spec sheet the focal length is 74.9mm.  Alpa calls it a 75mm, yet lists the spec as 73mm.  Confused yet?  Smiley

You really can't go wrong with any of the three lenses available in that range:
Rodi 70 hr
Schneider 72/73/75 - whatever
Rodi 90 hr

The 90mm is new and supposed to be very good and would have the least amount of color cast because it is the longest focal length.  Frankly I would choose based on preferred focal length.  On the 70-ish end the Rodi will have a little less cast, but the Schneider will be a bit smaller which is nice.  On the 90-ish end the Rodi would probably be the way to go.  The only one of these I own is the Rodi 70hr.  Fantastic lens, but they all are in this range!

Dave
Logged

weinlamm
Jr. Member
**
Offline Offline

Posts: 74


« Reply #12 on: October 30, 2013, 05:25:07 AM »
ReplyReply

Hi,

You can use the Adobe DNG Flat Field plug-in for Lightroom for the correction of light fall-off and color cast.

Cheers,
Bart

Thanks a lot for this link!

For MF I use Capture One DB-Version - but for some Leica-lenses there wasn't a good way; Cornerfix didn't work very well - I needed to work much more. I had thought about buying C1-Pro... But now - it's perfect!

So thanks a lot!  Smiley
Logged
Paul2660
Sr. Member
****
Offline Offline

Posts: 1713


WWW
« Reply #13 on: October 30, 2013, 08:00:32 AM »
ReplyReply

If you are using a Phase One back Capture One is free.  The. Pro version works with other camera files than Phase One.  You can download the Pro version for a 60 day trial.  The DB version is free and works only with Phase One digital back files.

The LCC process with Capture One is an excellent process and I prefer it to the LR plugin. 

Paul Caldwell
Logged

Paul Caldwell
Little Rock, Arkansas U.S.
Photography > http://photosofarkansas.com
Blog> http://paulcaldwellphotography.com
Pages: [1]   Top of Page
Print
Jump to:  

Ad
Ad
Ad