How to apply lens correction without lens metadata
When using a DSLR camera or a Phase One camera, lens metadata information will automatically be added to the RAW file. From the lens metadata, Capture One Pro 9 will know if it is a supported lens and, in case it is, automatically apply lens corrections to the image.
When using an older manual lens, for instance via a simple adapter, or perhaps using a technical camera, there will be no metadata describing the lens.
Other data like the aperture used for the exposure of the image is also missed, so lens correction will not automatically take place.
Using a technical camera with lens movements makes it even more challenging when lens corrections need to be applied. Despite not having proper lens metadata in the RAW file, the Lens Tool in Capture One Pro 9 still has some options for applying lens corrections.
Using a 100% mechanical lens
In the first example, I have been using a 100% mechanical and manual lens on a Phase One Camera and the raw file does not contain any information on lens name, focal length or aperture. Therefore, I have to make some notes or simply use my smartphone to document the shoot.
When you load the image into Capture One Pro 9 and look at the Lens Tool, it will just show a Generic lens profile without any default corrections.
Image will show up with a generic lens profile as no lens metadata has been savned into the RAW file
The lens used for this image shows a bit of barrel distortion, as well as some chromatic aberration, so I want to correct these artifacts.
For this image, I was using an older Phase One 45mm TS f/3.5 lens, which is a lens supported by Capture One Pro 9. To select the lens profile, I will have to pick it from the ‘lens profile list’ under ‘Phase One lenses’:
After the right lens has been selected, the image will automatically be corrected for Chromatic Aberration and distortion. If I had been using a lens that was not supported in Capture One pro 9, I would still have the possibility to do a chromatic aberration correction. If you would like more details on how to do this, read the following blog post:
When fixing distortion on a non-supported lens, you will have to try if either the Generic or the Generic pincushion lens model can fix it. For many lenses, you can actually bring down the distortion to a level where it is not noticeable any more, by using these generic lens profiles.
Furthermore, I will correct the keystone. Since this image has a dominant rectangle, I will use the Keystone’s cursor tool:
Next, I carefully place the four alignment circles on the corners of what I would like to be shown as a keystone free rectangle in the image.
To finish the image, I did a minor color adjustment on the blue sky with the Color editor.
Using a technical camera with lens movements
In the second example, I have been using a technical camera to create a keystone free image of a building by shifting the lens 5 mm up. I was using the Rodenstock ALPA HR Alpar 4.0 35mm lens; a lens that is supported in Capture One’s Lens Correction Tool.
Even though the image was taken with lens movements, it is still possible to correct for light fall off, chromatic aberration and distortion, as long as Capture One Pro has the information about the lens movements and the aperture. The raw file does not contain any metadata information on the lens, the aperture or the movements of the lens, so I have to record this information, as mentioned previously.
In the lens correction tool, I do the following:
- Select the lens used for the shot in the drop down menu
- Enter the movements and aperture in the movements tab of the Lens Correction Tool
- Apply LCC correction as explained in an earlier blogpost https://blog.phaseone.com/3-easy-steps-fixing-sky-skin-tone-tool/
In this case, the movement is 5 mm up so I enter +5mm for Y shift.
Final image after LCC-, lens correction and a bot of Color Editor work
It can be a little more challenging to decide the sign for the movements when doing horizontal movements. Here, the rule is that if you stand in front of the camera, the lens movement to the left is “-“ and movement to the right is “+” – like on a classic XY coordinate system. But, if you mount the camera in portrait mode, you may lose track of the directions of the movements, as up and down shifts now should be interred as shifts in the Y direction.
A simple trick
Actually, there is a trick to determine the right sign (+ / -) when entering the movements:
- Clone a variant of the LCC image and desaturate the image to get rid of any color variation
- In the Lens Correction Tool, select the lens used for the image
- Set the Light Fall-off compensation to 120%. The light fall-off compensation use the shift values to determine the right compensation
- Use the Levels tool to increase the contrast by dragging the shadow slider. This is only to make it easier to see the effect of Light Fall-off compensation
- Enter the Shift amount used for the image. If the image now appears with more even light distribution, you have entered the shift value in the right sign (+ / -)
- Try the opposite just to verify that you actually did it correctly
In the above example, I am testing according to the description above, whether to use + or – in my movements. In this case, shift Y at = +8 leads to a much more even LCC file than if I entered -8, indicating that +8 is right.
May 27 2016
By The Image Quality ProfessorCategory: Professor Tips Tags: Lens correction Capture One Pro 9 RAW files Lens movements Lens Metadata