P: Normalize focal lengths to 35mm equivalent field of view (instead of "literal" EXIF values)

[Carlos_Oliveras]

[I have rewrited this since the original post, since my original text was not as clear as it should be]

I think we all photographers refer to focal lengths in 35mm equivalent value (angle of view). But since there are a myriad of sensor sizes (and so, a myriad of crop factors), most of the time the Focal Length metadata (the "real" value) is not very useful, unless you only shoot full frame.

There is another metadata field called "Focal Length 35mm", but unfortunately, this field is only populated for some cameras (it never shows for any of my Canon cameras, for instance).

I understand this is not Lightroom Classic's fault, but some camera makers' (who, for some reason, are not filling in this field). But still, I reckon that some kind of fix is needed, since I think most of us think in terms of 35mm angle of view equivalent, and just seeing the "real" focal length is hardly informative. For instance, how many of us would like to base their lens-buying decisions on their most used focal lengths? Me, for instance, but I can't because of this.

But here comes another problem: even when this "Focal Length 35mm" field is populated, it is not available everywhere - unless I am missing something, I can't display this 35mm equivalent:

• As part of the info in Loupe Overlay
• As part of the info in Grid Extras overlay
• As a Metadata column filter (there's a plugin by Jeffrey Friedl that fixes this specific issue)
• Under the histogram (only "real" focal length is shown)
• In the Map module, in the small thumbnail pop up that appears when clicking the photo's orange pin in the map (only "real" focal length is shown)

I guess there could be at least 2 approaches to fix this:

- Force-populate the "Focal Length 35mm" when it is empty, and make small modifications where necessary to allow us to display it everywhere where we can also see "real" focal length

- Keep things as they are but provide a preference so that "Focal length" is always converted and displayed as its 35mm equivalent

There could be other options of course, but whatever the solution, I think something should be done, since the current situation doesn't make much sense - the "real" focal length, which like I said only makes sense for full frame cameras, is being featured everywhere, while the 35mm equivalent angle of view, which is what most of us (if not all of us) use and care for, takes a back seat or isn't there at all.

Maybe this wasn't such an issue when Lightroom Classic first came out, but nowadays, like I said, we have a ton of sensor sizes (both cameras and smartphones), and "real" focal lengths by themselves have come to mean very little.

Thank you so much for considering this idea!

[DdeGannes]

I you an Olympus camera and all my lenses are 2x equivalent, so it's not an issue for me, however I believe it would be useful to other who my be using multiple cameras. Have ticked upvote.

[Jim Wilde]

The frustrating thing is that there already is a Metadata field called "Focal Length 35mm", and which does appear in the LR Metadata Panel when displaying EXIF or EXIF+IPTC. The problem is that it only displays the 35mm equivalent value for certain cameras....e.g. it displays it with images from my old Olympus E-M1 and my even older Panasonic DMC-FZ1000, but stubbornly refuses to display it for any of my old APS-C Canon cameras. I assume it requires the camera/lens manufacturer to include the information in the lens data which eventually gets passed to LrC, so I guess that Canon for one don't do that.

[DdeGannes]

Ok, thanks Jim I am using a Olympus OM-D E-M1 also but do not have the option selected for display in the metadata panel. Good to know it's available.

[Carlos_Oliveras]

Hey Jim: I was under the impression that this field ("Focal Length 35mm") was always empty, but since you mentioned the Panasonic DMC FZ1000, which I also own, I've checked it, and surprise, this field does work for that camera. But it does not work for any of my Canon APS-C captures (neither for smaller sensor Canons like the PowerShots, G series, etc.).

[I have edited the original post to reflect that this field does exist, but it's not reliable since it may or may not work depending on the camera]

Maybe it would be possible to automatically populate this field when it is empty, but also, make it available everywhere, since even for cameras like the FZ1000, I still see no way to show it in the grid/loupe overlay, much less under the histogram. 😔

Thanks DdGannes for your suggestion about multiplying 4/3 focal length by 2, but I have never had a 4/3 or micro 4/3 camera. Still, even if I had one, I'd still like to see the equivalent focal length everywhere and spare myself of mental calculations 😅 (But it's true that finding the 35mm equivalent is easier when it's just a matter of doing such a simple calculation)

Thanks for your comments! 👍

[GoldingD]

I imagine that the  metadata Focal Length 35mm is populated by the camera, and not all camera manufactures feel the need to input that bit if data. Would not be surprised if some manufacturers have their own field not per standards that they fill in, but not read by LrC.

[Carlos_Oliveras]

Note: I have entirely rewritten my original text. I have realized my original explanation was a bit confusing, sorry about that.

Please upvote if you agree! Or provide your ideas about how to implement changes to correct this situation, because even if this "35mm Focal Length" field was force-populated somehow, it still wouldn't appear everywhere where it is needed (e.g. under the histogram, etc.).

So, while I think this is a very simple matter (it's just a multiplication, assuming that LR knows the crop factors for each camera), I think it requires some redesign in the way Lightroom Classic handles focal length values.

Thank you so much!

[DdeGannes]

For Canon and Nikon I believe the situation is a bit more complex for the original DSLR models, as opposed to newer Mirrorless models, since the lens mount allowed the use of earlier lenses which did not have electronic contacts so the lens info could not be transmitted.
I am referring to lenses pre digital these lenses are full frame but can be used on ACP model cameras.

Just a thought.

[GoldingD]

Perhaps:

http://regex.info/blog/lightroom-goodies/focal-length-sort

or:

https://www.lenstagger.com/documentation/how-to-use-lenstagger/

[Carlos_Oliveras]

Hey GoldingD,

Yes, the "Focal Lenght plugin" is already mentioned in my post.

As for lenstagger, not sure how it would help with this issue 🤔

Have a good one.

[JohanElzenga]

"For instance, how many of us would like to base their lens-buying decisions on their most used focal lengths? Me, for instance, but I can't because of this."

Why not? Your most used focal length is your most used focal length, regardless of whether you used it on a full frame camera or an APS-C camera. And if you specificly want to know what your most used focal length on your APS-C camera(s) is, then it is easy to set up a filter or create a smart collection for that.

[John R Ellis]

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To build on previous discussion, not all cameras record the EXIF field Focal Length 35mm. My test catalog includes sample photos from 111 distinct camera models, and only 78 of them recorded the EXIF field Focal Length 35mm:

(It may be that some of those other 33 camera models may record Focal Length 35mm with other lenses than used in the catalog's sample photos -- I haven't investigated.)

It's a straightforward calculation to use other EXIF fields usually included by cameras to compute the effective 35mm focal length.  The Exiftool utility will do that calculation for you,  and its tag Composite:FocalLength35efl displays EXIF:FocalLength35mm if it was recorded by the camera, otherwise it will display the calculated value.  However, if the pixels in the photo have been cropped or resized, the calculated value will be wrong. (LR cropping won't affect the calculation, since it doesn't affect the pixels in the master photo.)

You can use the Any Filter plugin's Filter command to see the computed FocalLength35efl:

Unfortunately, it sorts the column by the actual focal length, not the effective 35mm focal length, due to the way Exiftool displays those values.

[Carlos_Oliveras]

Hi Johan:

"Why not? Your most used focal length is your most used focal length, regardless of whether you used it on a full frame camera or an APS-C camera."

Sorry if I wasn't clear enough. I meant my most used focal length in 35mm. If we speak about "real" focal length (nominal, literal, whatever we may want to call it)... then maybe my most used focal length is 10mm. But:

- A few of them were shot with my Sony RX100 (1" sensor) at 10mm (which is aprox. 28mm in 35mm)

- Many of them, with my Canon 5D Mk II at 10mm (=10 mm since it's a full frame camera)

- The rest of them, with a micro 4/3 camera at 10mm (which I think equals 20mm in 35mm)

Then, say I want to buy a lens for my APS-C camera - would it be a good idea to buy a 10mm lens, based on this data? (15mm or 16mm equivalent in 35mm, depending on the APS-C camera maker). It's the same focal length? Yes. But it will render a different angle of view if compared to any of the images I based my decision upon, which is what matters to most of us. Well, at least to me! 😅 Therefore my suggestion about being able to always work with 35mm equivalent values.

As for building a smart collection or filtering by Metadata, of course, that would be ideal. But again, if we are speaking in 35mm terms, I can't filter or make a Smart Collection if the 35mm equivalent data isn't there in the first place 😟 - like I said, this field isn't populated for all cameras. And even when it is there, I can't use the Metadata filter and filter by "Focal Length 35mm" unless I use a plugin (still, I can make a Smart Collection, but then again, the "Focal Length 35mm" data must be there already).

Hope I made myself clear, excuse me otherwise, since english is not my native language.

Have a great day!

[Antoine HLMN]

Let me add my voice to this request 🙂

1. Yes, we all know the difference between physical focal length and 35 mm (or full frame) equivalent focal length, which is used as an indication for the field of view.
2. As mentioned previously (Jim Wilde), the equivalent focal lenght is already available in the metada fields.
3. Many photographers use various cameras, ranging from phones, drones, ... up to full frame or even bigger. Having the ability to filter through all of these would be great. Not to mention (much) older cameras which used to have smaller sensors. I'm not an expericed photohrapher nor am I a pro. And yet, my library contains a zoo of cameras and lenses:
4. Comparing field of fiew is usually more important or makes more sense than real focal length. Especially when shopping for a lens.
5. Could even make sense on full frame bodies when the crop mode is enabled. Images from the same body+lens combo would then be discernated, whereas they're not when you filter based on the focal length only.
6. Since the data is already available, adding this to the filter feature should be pretty easy

And if we want to enter that rabbit hole, we could also have the same for the aperture 🙂