Focal Length in Photo Info

Allen

Can we drop the parenthesis with bad info. Hasn't been working for some time.
Canon 500 lens with zoom extension

Focal Length 500.0 mm (500.0 mm in 35mm)
Focal Length 700.0 mm (700.0 mm in 35mm)
Focal Length 1000.0 mm (1000.0 mm in 35mm)

Can this be really correct for iPhone 8+?
Focal Length 4.0 mm (28.0 mm in 35mm)

Jtring

A quick web search tells me a crop factor of 7 is about right for the Iphone. SmugMug correctly folds in the crop factor of 2 for my micro four-thirds camera. All bets are probably off if you are using an extension tube or digital cropping (or cropping in post for that matter) since it may not be possible to pull those out of the EXIF.

kurzvorzwoelf

@Jtring said:
A quick web search tells me a crop factor of 7 is about right for the Iphone. SmugMug correctly folds in the crop factor of 2 for my micro four-thirds camera. All bets are probably off if you are using an extension tube or digital cropping (or cropping in post for that matter) since it may not be possible to pull those out of the EXIF.

Hm, for what it's worth - SmugMug doesn't recognize the crop factor of my Oly OM-D EM-10II correctly, i.e. as Focal Length: 40.0 mm (40.0 mm in 35mm), so I found this information quite pointless so far as well.

Jtring

I do wonder what is going on. I can see the incorrect information on your site. Yet my wife also uses an EM-10Mark2, and SmugMug reports the crop factor correctly for her. (She mostly uses the 14-42 F3.5-5.6 lens.) LIkewise, all is correct with my current Panasonic G85 and with the Oly EM-5 Mark1 I used a few years back. There may be a difference in post-processing. We both use Lightroom to post-process and upload. Clearly there's a bug here somewhere, but it's not universal.

leftquark

If you see any errors, feel free to pass them along. We use a tool called "Exif Tool" to pull metadata out of a photo, so it's the gold standard for extracting information -- if anything is amiss we're constantly working with them to iron out anything.

Allen

I would think all you need is the camera and focal length. Camera defines crop factor. CF x FL = mm in 35mm
Both are defined in the EXIF.

leftquark

That’s essentially what ExifTools does

kurzvorzwoelf

@Jtring said:
I do wonder what is going on. I can see the incorrect information on your site. Yet my wife also uses an EM-10Mark2, and SmugMug reports the crop factor correctly for her. (She mostly uses the 14-42 F3.5-5.6 lens.) LIkewise, all is correct with my current Panasonic G85 and with the Oly EM-5 Mark1 I used a few years back. There may be a difference in post-processing. We both use Lightroom to post-process and upload. Clearly there's a bug here somewhere, but it's not universal.

Hm yes, I just conducted a quick test on two (different) pictures, taken with same camera, lens & even same FL, exported from RAW, using two different post processing tools. While one certainly has the data in the EXIF retained, the other does somehow not:

First
$ exiftool.exe 2018-08-10\ 19-40-21\ -\ P8100002_DxO.jpg | grep -i 'focal length'
Focal Length : 40.0 mm
Min Focal Length : 12
Max Focal Length : 40
Focal Length : 40.0 mm (35 mm equivalent: 80.1 mm)

Second
$ exiftool.exe Dike\ Minimalism/2019-01-02\ 15-25-50\ -\ 0182.jpg | grep -i 'focal length'
Focal Length : 40.0 mm
Focal Length : 40.0 mm

First was processed using DxO (version I cannot remember), second one was processed using combination of ACDSee 2019 & ON1 PhotoRaw (which I process basically 99% of my images with). So indeed, it seems to be a problem with one of the tools fiddling too much with the Exif data embedded in the pictures, not a SmugMug issue. Will have to find out which program is responsible for that, and possibly file a bug report (I also had issues with one of the tools replacing the Lens Exif data with what it deemed correct in the past, that was very annoying at times).

Ferguson

Why is smugmug buying into the camera manufacturer's BS that focal length changes with crop factor. It doesn't. 24mm is 24mm no matter the camera. Field of view changes, but not focal length.

leftquark

@Ferguson said:
Why is smugmug buying into the camera manufacturer's BS that focal length changes with crop factor. It doesn't. 24mm is 24mm no matter the camera. Field of view changes, but not focal length.

I'm confused -- we display both the focal length as reported by the camera, plus the focal length converted to 35mm since the 35mm equivalent is what most people use as a frame of reference. One is the original ... the other is what everyone wants to read it as. Both are displayed. Everyone can be happy.

Ferguson

It's only a mild chiding... focal length is focal length. There is no "equivalent" focal length. There is a "focal length which on a 35mm size sensor will yield the same diagonal angle of view".

I just think that generally speaking serious photography sites might consider educating their users instead of buying into the whole false "equivalency" thing. Otherwise when they start trying to understand things like DOF they will remain baffled with crop conversion factors misplaced.

I do realize it is widely accepted, even part of some standards... it's just misleading. And every once in a while I feel like playing Don Quixote and taking on a few windmills. Like when people use say a kilogram is 2.2 pounds.

We now return control of your set to the regularly scheduled program.....