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Friday, March 10, 2006

A Modest Terminology Proposal

The Online Photographer would like to propose a modest but sensible change to the common terminology of digital imaging. I would propose that measured focal lengths of lenses continue to be referred to in "mm" (millimeters) for their actual focal lengths, but that, henceforth, we use the term "mm-e" to mean "millimeter equivalent," with the understanding that the equivalent intended is 35mm.

Thus, a 24mm lens on an APS-C sensor would be 24mm, but 36mm-e.

This seems an easy and unabiguous way to denote something we all already do anyway.

If this proposal makes any sense to you, please forward it to anyone appropriate you might know, including webmasters of photo sites, editors of photo magazines, forums you frequent, and so forth, to see what others think.

Posted by: MIKE JOHNSTON

17 Comments:

Anonymous Josiah Davidson said...

KUDOS!
Great idea!

7:00 PM  
Blogger carpeicthus said...

Workable, maybe, but it doesn't mean all that much, since "mme" would not be an actual quality of the lens, whereas mm very much is. I'd prefer a term not so easily confused or mis-typed with mm.

7:17 PM  
Anonymous rennie12 said...

I have for some time used this:

35mE - which is sufficiently self-evident to use without explanation.

I am NOT suggesting it's better - I don't think it matters WHAT we use, but we DO need a generally accepted abbreviation for what has become a defacto standard.

8:37 PM  
Blogger Dan said...

A solid idea but I agree that "mme" is too similar to "mm" that it can get confused. A simple way to further differentiate it more would be "35mmE."

I would have no problem adding that to my site's glossary.

8:44 PM  
Anonymous Peter said...

Too bad we don't use angle of view. We wouldn't need mme, but could use the angle instead.

10:38 PM  
Anonymous Anonymous said...

I would also like to see the angle of view, it would make the comparasion of lenses so much easyer, one coud even easyly compare compact digicams to SLR-s whitout calculating. And it would make it much easyer to explain things to nonphotographer...

1:42 AM  
Anonymous John said...

Many years ago, when I worked at BBC television in London, we had a variety of different cameras with different sized sensors. All had to use different focal length lenses to achieve similar image coverage across camera types. So we referrred to them by their horizontal angle of view: 35 degrees, 25 degrees, 12 degrees and 8 degrees. Simple but meaningful. The terms 'mm', 'mme' and 'mmE' only mean anything to those brought up the full-frame 35mm film camera way. Think to the future - to those not yet into photography - and let's not increase confusion any longer for those who are. Start a campaign for lenses to be marked in horizontal angles of view and you can definitely count me in.

2:08 AM  
Anonymous Dierk said...

Well, since the actual physical characteristic denoted by, say, '50 mm' isn't changed at all - the focal length of a lens stays the same regardless of the area of the image circle used by the light-sensitive recording device - I don't think 'mme' or any similarly confusing term is practical.

Since only the angle of view is changing (in-camera crop) I find John's idea much better.

It will be difficult enough since the originally problem - lot's of different in-cam-crop factors - doesn't go away; you still need to list a table for third-party lenses like Sigma's.

3:10 AM  
Anonymous Anonymous said...

It'll never catch on, I tell you. Just like "bokeh".

6:01 AM  
Anonymous John said...

Gotta agree that it's a bad idea.

In another 5 years (if this isn't true already) most SLR users will have never used a 35mm (or digital FF) SLR. It would then likely make more sense to refer to a 35mm lens on a FF sensor as a 24mmE, because that's the frame of reference for most photographers.

7:48 AM  
Anonymous Andy Farrell said...

Not sure I agree. Having never really used a 35mm film camera almost my entire experience with SLRs is digital, thus to me a 30mm lens is normal, 18mm is moderate wideangle and 50mm is a mild telephoto.

135-equivalence doesn't really mean much to me.

9:19 AM  
Anonymous Anonymous said...

I like it - the Sony R1's lens is actually marked in 35mm equiv - I'm glad it's like that. The EXIF reports the actual FL.

Steve H.

10:56 AM  
Blogger Mike Johnston said...

The reason angle of view won't work is that it's only a property of a lens in one format. The same lens can be put on several different cameras, and might have a different angle of view on each. Then you're stuck with the original problem, which is that you'd have to specify at length what you meant, rather than just being able to give a quick shorthand label.

--Mike

11:33 AM  
Anonymous Anonymous said...

David Cardinal of nikondigital.org said it could catch on.....

8:40 PM  
Blogger bokeh said...

I prefer VAV - vertical angle of view. For instance: how tall would a standard doorway be if I use this lens on this format or which VAV is best for portraits? You could use the same lens on a 3:4 format or a 2:3 format or a 16:9 format, it would still have the same meaning. Only Canon users with their FF, 1.3 crop, 1.6 crop sensors all using the same lenses would have a problem. Of course who says it has to be engraved on the lens, put it in software and let the camera do the math.

11:37 AM  
Anonymous Jordi Bunster said...

Too 35mm centric. Better to drop 35mm as the reference, and learn to deal with different formats, such as APS-C, DX, 4/3, etc. No different than 135, 120, 8x10 ...

11:11 PM  
Anonymous G Kramer said...

I'm dubious. A 50mm image on an APS-S sensor is just a fullframe image, cropped 2/3 (linearly); similarly, one in the D2X's High Speed Crop mode is just one cropped somewhat more (about 1/2 linearly). And if one applies a subsequent "artistic" crop to improve the composition, it's something still different--are we to invent new names for each possible crop?

10:30 PM  

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