Phocus LCC

[epines]

A few questions about creating LCC / "scene calibration" shots for Phocus (FYI -- I'm shooting with a Schneider 35mm Digitar XL on an Arca Swiss 69 FC; back is an H3D-39 II):

- Do I actually need to create LCC shots for every image I want to correct, on location, under the same lighting, conditions, etc.? If the LCC shots are only for correcting the aberrations created by the lens -- rather than unevenness in the lighting of the scene -- why not just have a library of LCC shots saved for each lens at varying degrees of shift?

- If I use Phocus's "equalize intensity" setting, will it ONLY equalize vignetting caused by the lens, or will it also remove any unevenness in the scene itself? Meaning, let's say I'm shooting a scene whose left side is (deliberately) much brighter than its right. When I create the LCC shot through my opaque white plastic, will Phocus see the darker area on the right and try to correct it? This is why it seems wiser to create a library of LCC images against an evenly lit background, rather than in the actual location.

- I'm using the opaque white plastic card sold by Capture Integration. Can I use it for white balancing as well? Once I've applied the scene calibration, is my shot white-balanced? Or should I be doing a separate grey-card shot?

thanks
ethan

[Douglas Fairbank]

Here is a link to a Hasselblad help guide that I think will answer your questions. Seems to be to big to upload even though it is inside the limit for attachments.

https://www.dropbox.com/s/3366z5zoys8plir/Scene%20calibration%20tutorial.pdf

[epines]

Thanks, Douglas. It answers some of the questions. Much appreciated.

ethan

[jonathan.lipkin]

Ethan, have been using an HTS for about two years now. I've found that the images need correction more when shift is used than if tilt. In fact, I see very little change when doing small (<2degree) tilts.

Observations below are based on my experience and a few conversations I've had with Hasselblad reps.

A few questions about creating LCC / "scene calibration" shots for Phocus (FYI -- I'm shooting with a Schneider 35mm Digitar XL on an Arca Swiss 69 FC; back is an H3D-39 II):

- Do I actually need to create LCC shots for every image I want to correct, on location, under the same lighting, conditions, etc.? If the LCC shots are only for correcting the aberrations created by the lens -- rather than unevenness in the lighting of the scene -- why not just have a library of LCC shots saved for each lens at varying degrees of shift?

Yes. Why? Dunno. Seems to work better that way. Sometimes when I forget to shoot one in the field, I shoot in the studio using daylight fluorescents and it comes out ok.

- If I use Phocus's "equalize intensity" setting, will it ONLY equalize vignetting caused by the lens, or will it also remove any unevenness in the scene itself? Meaning, let's say I'm shooting a scene whose left side is (deliberately) much brighter than its right. When I create the LCC shot through my opaque white plastic, will Phocus see the darker area on the right and try to correct it? This is why it seems wiser to create a library of LCC images against an evenly lit background, rather than in the actual location.

I've never found that the equalize intensity does much of anything at all. It sometimes tries to correct for vignetting, but over-corrects, so I usually leave the box unchecked

- I'm using the opaque white plastic card sold by Capture Integration. Can I use it for white balancing as well? Once I've applied the scene calibration, is my shot white-balanced? Or should I be doing a separate grey-card shot?

I use a piece of opaque plexi I bought at a plastic shop for $7. I probably should buy another one as a backup.

The images I shoot are outdoors, so I don't do an enormous amount of white balancing. I have shot a gray card as well. I don't think the plexi/card white balances, it just provides a reference to how the colors are getting changed by the geometry of the HTS. Not 100% sure about this though.

One last thing - you'll have to over-expose the calibration images by about 1.5-2 stops for best results. If they are shot at the same exposure as your scene, you may get a message saying that the image is too dark. You could try adjusting the brightness in Phocus, but I'm not sure how that would affect the results.

[Steve Hendrix]

A few questions about creating LCC / "scene calibration" shots for Phocus (FYI -- I'm shooting with a Schneider 35mm Digitar XL on an Arca Swiss 69 FC; back is an H3D-39 II):

- Do I actually need to create LCC shots for every image I want to correct, on location, under the same lighting, conditions, etc.? If the LCC shots are only for correcting the aberrations created by the lens -- rather than unevenness in the lighting of the scene -- why not just have a library of LCC shots saved for each lens at varying degrees of shift?

- If I use Phocus's "equalize intensity" setting, will it ONLY equalize vignetting caused by the lens, or will it also remove any unevenness in the scene itself? Meaning, let's say I'm shooting a scene whose left side is (deliberately) much brighter than its right. When I create the LCC shot through my opaque white plastic, will Phocus see the darker area on the right and try to correct it? This is why it seems wiser to create a library of LCC images against an evenly lit background, rather than in the actual location.

- I'm using the opaque white plastic card sold by Capture Integration. Can I use it for white balancing as well? Once I've applied the scene calibration, is my shot white-balanced? Or should I be doing a separate grey-card shot?

thanks
ethan

Phase One refers to their cast correction process as LCC. You cannot use this same name for Phocus. The Scene Calibration tool in Phocus is the equivalent, so you just refer to the Phocus version as SceneCal.

Ok, just kidding. Let's use LCC. You could have a library of LCC's, but generally this would not eliminate the need to perform LCC's as there are so many variations, the library would go on for quite some time. However, you could have some standard iterations. Example, ideally, an LCC would be created at least for any change in aperture or change in the position of the lens relative to the sensor. So you could potentially have LCC's that range from f8 - f16, and then combined with movements (which could be many, such as 5mm shift right, 4 degree tilt). You could have 40 - 60 combined left/right shift/rise/fall movements just with the 4 degree tilt alone. And then times the number of different apertures. But I'm with you - you could certainly have at least some common situational movements at some base apertures, say f8, f11, f16 and 5mm shift right, 10mm shift right, 5mm shift left, 5mm shift left. Etc.

If the Scene Calibration for Equalizing Intensity in Phocus works similarly to Capture One's LCC, then you would actually cover the scene itself with white something (foam core, etc), rather than hold a plexi against the lens. And the purpose of this would be yes, to equalize the illumination in the scene (like for copy work). That is why it is recommended to un-check the Vignetting tool in the DAC Toolbox.

Thank you for using our Capture Integration LCC card. It may work ok as a white balance tool. However, it is not a spectrally neutral element, so it will not be as effective in neutralizing white balance as, say, an Xrite Color Checker, Passport, etc.


Steve Hendrix