The new-ish Nikon Z series of cameras and lenses contain distortion and vignette correction in each raw file, the same as other manufacturers such as Sony and Fuji are doing.
The upside is that you don’t need to profile every lens for inclusion in lensfun anymore, it the downside is that we will need to reverse engineer what that metadata means and the formulas used, as like other manufacturers, Nikon hides this information behind an NDA. And NDAs and FOSS code do not go together. Actually I don’t know that the information is in the Nikon SDK because you have to agree to the NDA before you are considered for having access to the SDK. But I assume the information is in there.
I’ve emailed both Nikon USA and the corporate feedback for the SDK to express my displeasure at the NDA and the lack of freely available information for a camera that I just spent thousands of dollars on. This of course did absolutely no good.
So here I will begin collecting information and try and figure out what the metadata means so that eventually we can have support for Nikon Z lenses and cameras.
Please, Nikon Z users, join me!
20 Likes
As documented in the exiftool source code , the distortion and vignette correction is here:
# extra info found in IFD0 of NEF files (ref PH, Z6/Z7)
%Image::ExifTool::Nikon::NEFInfo = (
GROUPS => { 0 => 'MakerNotes', 2 => 'Camera' },
NOTES => q{
As-yet unknown information found in SubIFD1 tag 0xc7d5 of NEF images from
cameras such as the Z6 and Z7, and NRW images from some Coolpix cameras.
},
# 0x01 - undef[12]
# 0x02 - undef[148]
# 0x03 - undef[284]
# 0x04 - undef[148,212]
# 0x05 - undef[84] (barrel distortion params at offsets 0x14,0x1c,0x24, ref 28)
# 0x06 - undef[116] (vignette correction params at offsets 0x24,0x34,0x44, ref 28)
# 0x07 - undef[104]
# 0x08 - undef[24]
# 0x09 - undef[36]
);
Colin_Adams
April 19, 2023, 5:16pm
3
Can I do anything to help? I have a Nikkor 24-120 f/4 S Z lens.
Jade_NL
April 19, 2023, 5:18pm
4
I have the 35mm F/1.8 and 24mm F/1.8 S Z lenses.
As Colin, I’m not sure how I can help, though.
I have the following Z lenses:
50 mm f1.8s (this has lensfun correction data available)
24 mm f1.8s
100-400 f4.5-5.6 VR S
First thing to do is to dump the metadata that exiftool has listed.
I’ll put it into a spreadsheet as people start reporting numbers.
Second thing to do would be to try known formulas for correcting lens distortion and vignetting with the metadata dumped from the Nikon raw files.
ggbutcher
April 19, 2023, 7:30pm
7
I want to help, but I’ll not be with my primary computer for a few weeks.
It is likely the values line up with the parameters required for the Adobe DNG opcode3 distortion correction function. I took a Z 6 NEF and DNG converted it, that’s as far as I got…
2 Likes
Jade_NL
April 20, 2023, 6:05am
8
Here’s the 0xc7d5 specific datablock for the:
Nikkor Z 24mm f/1.8 (2.6 KB)Nikkor Z 35mm f/1.8 (2.6 KB) This one is also in the Lensfun database.
Probably not relevant but both shots used are from a Z6ii
kmilos
April 20, 2023, 8:30am
9
Please note that, once decoded, someone will also need to enable accessing these blocks from exiv2 (for dt and soon RT to benefit).
Colin_Adams
April 20, 2023, 1:00pm
10
What command do you use to produce this dump?
Jade_NL
April 20, 2023, 1:40pm
11
I used this:
exiftool -v4 image.nef
You do need v4, v3 will truncate some stuff. It will spit out about 1600 lines in a semi ordered fashion. For both my lenses and using my Z6ii the block of interest sits between lines 158 and 187.
1 Like
kmilos
April 20, 2023, 1:45pm
12
Or even -v5, depending on the size of the chunk (so this just keeps pushing the truncation threshold)…
Colin_Adams
April 20, 2023, 1:47pm
13
Here is the 0xc7d5 block for the Nikkor Z 24-120 f’4 S:
| | 17) NikonNEFInfo (SubDirectory) -->
| | - Tag 0xc7d5
Colin_Adams
April 20, 2023, 1:51pm
14
Hm. It seems to differ according to focal length. That one was for 24mm. Will I need to take photos at a range of focal lengths?
Jade_NL
April 20, 2023, 1:51pm
15
Good point!
I jumped the gun with -v4 based on my 2 lenses, with both have a block that is the same size.
The amount of data seems to be mentioned (undef[448] for both my lenses and as I see now, undef[976] for Colin’s lens.
EDIT
@Colin_Adams :
Zoom vs prime lens, I guess. Not sure what to advise you about this.
kmilos
April 20, 2023, 1:59pm
16
As this is just another TIFF IFD structure, exiftool smartly parses it further if you give it the -u option:
Nikon_NEFInfo_0x0005 : 0100..šY...y†.Wãþÿ.Ir..[...]
Nikon_NEFInfo_0x0006 : 0100..šY......v...)Ó.[...]
Nikon_NEFInfo_0x0007 : 0100..šY...œúÿÿ.r...Sÿÿÿ..[...]
Nikon_NEFInfo_0x0008 : 0100h...þÿÿ.±œ
Nikon_NEFInfo_0x0009 : l.........Õ6
Nikon_NEFInfo_0x000a : 0100ð.ð.ð.ð.@¬
Nikon_NEFInfo_0x000b : 0100..@ €.=.
Nikon_NEFInfo_0x000c : 0100lµ
Nikon_NEFInfo_0x000d : 0100.<;
Nikon_NEFInfo_0x000e : 0100F0...."·*ªàr^‘.õ.™e‚𯿠ÒÒ/ÆÁ.§†ÅZ!XئÊ6ìL
Nikon_NEFInfo_0x000f : 0100ž£
albeit w/ unknown tags (also seen in -v4/-v5 output).
Going by existing Nikon MakerNote fields, the 4 first bytes usually denote a version of some block/struct, so “0100” probably means “1.00”.
Colin_Adams
April 20, 2023, 2:05pm
17
Hm. That is more readable?
I see:
Nikon NEF Info 0x0005 : 0100…<9A>Y…V<99>…t.G@…[…]
.#.h+#ʚ ;{<84>%.ʚ;]tfʚ;<8F>.ʚ;?x>ʚ;.ʚ;<98>[…]
Colin_Adams
April 20, 2023, 2:09pm
18
BTW, lensfun has data for this lens.
Jade_NL
April 20, 2023, 2:10pm
19
Those are not the correct tags that are shown by -u. Or more specific the tags we are looking for.
The first one (0x0005), for example, is this one in the -v4/5 output:
| | | 2) WhiteBalance = AUTO1
kmilos
April 20, 2023, 2:13pm
20
The two bytes just after the “Nikon\0” header seem to also indicate some version number of this directory:
- Tag 0xc7d5 (976 bytes, undef[976]):
| | 3fa28: 4e 69 6b 6f 6e 00 01 03 00 00 49 49 2a 00 08 00 [Nikon.....II*...
So it would be “1.03” here. I’m e.g. seeing “1.02” on the Z 9 sample on RPU…
(For the traditional MakerNote way below it is 02 11 for “2.11”.)
