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Bug #10121

lens correction behaviour when shooting in cropped mode

Added by Jozef Sivek about 4 years ago. Updated over 3 years ago.

Status:
New
Priority:
Low
Assignee:
-
Category:
Darkroom
Target version:
Start date:
09/24/2014
Due date:
% Done:

0%

Affected Version:
1.4.2
System:
Mac OS X
bitness:
64-bit
hardware architecture:
amd64/x86

Description

The lens correction seems to not take into account the (actual) crop factor of the camera. The full frame cameras can shoot in the cropped DX mode and programs like Hugin recognize the change of the field of view. It may be a lack of indication but the lens correction module should produce identical results, when full frame camera model shoots in cropped mode or cropped camera model is manually selected.

The least thing that can be done, is to actually indicate if the given picture was taken in the cropped mode. Then, if applicable, the information can be used to properly adjust lens corrections.

History

#1 Updated by Torsten Bronger about 4 years ago

One possibility is to detect the crop factor from EXIF data, and pass this crop factor to lf_modifier_new() instead of the camera's crop factor as returned by Lensfun. This crop factor needs to be stored in the database/XMP file.

#2 Updated by Pascal de Bruijn about 4 years ago

  • Target version set to Future

Considering this is a fairly obscure feature, only supported by a few pricey Nikons, so I'm not surprised we don't have this covered yet.

Apparently rawsamples.ch has some samples, and it seems Nikon stores it fairly nicely in EXIF:

RAW_NIKON_D800_14bit_1.2x-30x20_UNCOMPRESSED.NEF Exif.Photo.DigitalZoomRatio Rational 1 1.2
RAW_NIKON_D800_14bit_5x4-30x24_UNCOMPRESSED.NEF Exif.Photo.DigitalZoomRatio Rational 1 1.1
RAW_NIKON_D800_14bit_DX-24x16_UNCOMPRESSED.NEF Exif.Photo.DigitalZoomRatio Rational 1 1.5
RAW_NIKON_D800_14bit_FX_LOSSLESS.NEF Exif.Photo.DigitalZoomRatio Rational 1 1.0

#3 Updated by Torsten Bronger about 4 years ago

I suspect the Sony A7 has a crop mode, too.

The FinePix F810 has a "widescreen" mode.

The Panasonic DMC-LX{1,3,5} cameras have a 3:2, 4:3, and 16:9 mode.

#4 Updated by Pascal de Bruijn about 4 years ago

At least in Panasonics case, at least one dimension stays full size in each mode (if I recall correctly).

#5 Updated by Torsten Bronger about 4 years ago

You probably mean the "multi format sensor" of the DMC-GH1. This has very similar crop factors for all three aspect ratios. But for the DMC-LX3, the crop factors are 5.1, 4.7, and 5.75.

#6 Updated by Pascal de Bruijn about 4 years ago

IIRC all (panasonic) (m)4/3's cameras have this "multi format sensor" thing... It's merely the LX series that deviates in this regard (presumably because of lens design compromises?)...

#7 Updated by Malte Cornils almost 4 years ago

Torstens suspicion is correct, all of Sony's A7 series cameras have the crop feature (and if I recall correctly, also Sony's A-Mount full format cameras). I can verify that lens correction is not available on pictures shot with my A7s with a lens supported on APS-C Sony E-mounts.

In addition, it is possible to use those lenses without crop, since some APS-C lenses have a fairly large (almost FF) image circle. However, this corner case is probably not as important to support as the crop mode (which I use almost all the time now, effectively disabling lens correction).

#8 Updated by Torsten Bronger over 3 years ago

For the time being, one can select a NEX-7 although one shoots with an A7. But a clean fix is more complex and will take a long time. So far, we just add fake camera models (like "Sony A7 (crop)" or "Lumix XY (16:9)", however, this doesn't work with autodetection and is ugly in general.

#9 Updated by Malte Cornils over 3 years ago

OK, I feared as much, however the given workaround should satisfy my immediate needs - thank you! Please tell me if/when you need cropped example ARW files.

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