The same distant object becomes brighter as you bring it closer. Light decreases with distance (inversely to its square i.e.
Here's my "reverse-engineering" of Sirius formula: It can be trialed with watermarked output.ĭng output makes big difference for editing in Lightroom. If you're not using RAW dng scanning through Vuescan, I would recommend trying out Vuescan for this. They you can adjust gradient to get the same RGB values in corners. To adjust gradient to your liking when mouse is hoovered over white area in the center, RGB values will show bellow histogram in develop mode. If you find any images that need further correction, every single one can be fine tuned for that masked area only. Settings or mask itself can be copied to any images you have. Import in lightroom and add gradient maskģ. Acquire LCC image of white background (at multiple f stops if needed).Ģ. Masking is basically separate layer just like in Photoshop and isn't destructive.ġ. I find Lightroom way faster to work with images and only get them to Photoshop if I really have to. Masking option in Lightroom can be also set to gradient. It can be just held in front of the lens. That differential gets smaller at smaller apertures and corner density and colour casts will have different strength.įastest solution would be testing that filter on digital camera preferably on equivalent focal length for the format and lens with similar filter diameter. All this assuming that your center filters don't have colour casts.īoth of these center filters are fixed 1.5 stops and wide open there is probably more than 3 stops of fall-off. Shutters would have to be linear between f-stops and development would have to be perfect to get consistent results. Obviously there are quite few things that could go wrong when trying to do this with film.
#LENS TO REMOVE RED COLORCAST HOW TO#
There was a long procedure on how to do that and how to make calibration targets.
Correction lens profiles can be created for Lightroom. Not sure if this is nitpicking or related to properties of their digital sensors in different light but film could certainly respond differently since it's not linear. Phase One is recommending to create LCC profile during every shooting session and for every aperture. I didn't test it myself but making LCC profiles on film might not be feasible. there is still possibility of light polarization across image that manifests differently in far corners So there is differential in F stops and if center filter has a colour cast due to aging or inherent cast, 1.5 stops is just enough to cause visible colour cast.Ģ. both center filters for these two lenses are 1.5 stops. Since it's visible in corners only there are 3 possibilities:ġ. I still think that suggestion from my previous post about colour cast coming from filter is a further possibility to check.Įven Schneider's center filters could potentially produce colour casts compared to colour reproduction of the lens itself. If you used any filters, that might be potential culprit. Some filters are advertised to minimize color cast.
Polarizers will make it worse.Īlso if some other filters are used, for example UV or ND, edges could show any slight color cast in those filters. I did see something similar in certain situations with some Hasselblad and large format lenses.ĭoes this happen on all images taken with these or just in certain situations / similar light?įrom what I read there is natural polarization of light and it can be seen on images with wide lenses. I have some similar lenses but haven't used them extensively. Equivalent to LCC profile could be made but it's only effective on digital since you need to get it for each aperture and light could also change the color cast. Adjustment layer needs to be added and selections added as desired. Color temperature and other color controls are available to neutralize the cast. When selection is made mask is created and adjustments can be performed selectively only on this mask. Next step is to select brush and size and feathering can be adjusted. In develop module, under Histogram there is Masking tool (dotted circle on right).Įach corner can be masked separately if color cast is different due to light angle and it probably is. Latest lightroom has quite easy fix for this.
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