GH2 has an oversized MFT sensor, so 1.86 is the right number. BTW, this turns a 28mm closer to "normal focal length" than a 25mm (52.08mm vs. 46.5mm). Anyhow I doubt one will really recognize the difference in a blindtest. ;-) And yes, its confusing if people doing motion pictures refer to a fullframe sensor. But thats the way it is, at least in my place. I doubt adding more parameters to the equation would make it easier. All I really need to know is the crop factor of the cam and the focal lenght printed on the lens. (If diameter of projection is to small you will recognize first time you plug this lens on you cam... hello C-Mount...)

As rule of thumb just take original focal lenght by 2 and substract 1/10 of the focal lenght printed on your lens from your result. (f.e. 25mm * 2 - 2.5 = 47.5mm). This should be close enough. If you need to know more exact just half the last value in your equation and again substract it from your result (25mm * 2 - 2.5 - 1.25 = 46.25mm). As you can see we are only 0.25 mm away from the result the calculator spits out. I can do this in my head pretty quick unless its 6 in the morning and catering forgot about the coffee. ;)

@artiswar

35mm on a 135mm exposure area

You mean 135 film? No millimeters in it's name. Just 135 (or 120 for medium format etc). Just to prevent adding more mm's to the confusion :)

@Riker

I think of 35mm eq of 25mm

It would be 25/2=12.5mm. So you need a 12mm prime lens, or wide zoom.

I would agree wholeheartedly with @vicharris on this one and thank god I've found this thread, I thought I was the only one confused about the whole "full frame" calculations. Out of 270000 feature films listed on IMDB, 50 of them are shot full frame. 50. So this makes perfect sense.

vic's logic makes perfect sense, at least on a forum like this one, which is really 99% about GH2's video mode.

Just one thing, about going wide. When I say "wide" I think of 35mm eq of 25mm. That AOV is something I would consider wide. What lens would get that similar AOV in video mode on the GH2?

And to think at 5am every Monday morning after having a coffee with the loader and seeing which lens he'd popped on and guessing where I'd not be in shot, I should've got me calculator out ;p

I think it is also important to mention that FF sensors don't have any crop at all, right? So in my opinion those comparisons do make sense, since the FF equivalent tells us what field of view a particular lens produces if it isn't cropped at all. To me it seems like a nice standard to compare with.

@Sangye

Any cinematographer worth her salt should be familiar with the ratio of focal length to angle of view for the camera being used.

Well, cinematographers working with one camera format do - but the rest of us only carry around a few benchmarks in our heads. When teaching media, if I told students to "set your zooms to a 50mm equivalent" we got lots of different FOVs, with people dashing around to squint into each other's viewfinders, gasp and come to me to ask which one's right.

The reason why a change in jargon would be a wise thing now is that there isn't going to be a standardisation of sensor-size anytime soon.

@vicharris

This might be a dumb question but why the hell does everyone on all these boards compare every damn lens' focal length to full frame cameras?

The reasons for this industry practice are largely historical. We're currently in a transition period marked by two major developments:

1. The advent of digital still cameras: In the first generation of digital still cameras, the technology could not yet produce affordable digital sensors as large as the standard 35mm (full-frame) film cameras they were replacing. As a result, it was necessary for digital manufacturers to explain the lens FOV crop factors to ease the transition for still photographers. For example, Panasonic cites both inherent and "35mm equivalent" focal lengths in marketing its line of MFT lenses. Since a wide variety of photographic lenses are currently used to shoot DSLR video, the industry's full-frame comparisons are frequently used in video lens discussions.

2. The advent of DSLR video: The first video DSLR to achieve widespread prominence was the Canon 5D MkII, which has a full-frame sensor. One of its most notable features was its ability to produce narrow DOF using relatively slow photographic lenses. Many in the industry associate this effect with DSLR video in general, and regard the 5D MkII as the default reference for DSLR video. As a result, full-frame comparisons are frequently used in video lens discussions.

@artiswar+11111111111111 Yes, the first one who understands what the hell I'm saying and does not flame me off topic! And yep, you've probably opened a larger can of worms. Good luck with all these pro's with 40+ years of experience cutting you down! :)

@vicharris

Check your language.

@oscillian

Great remark! Let's calculate crop factors for the 5D vs. Linhof Tecnica…

Or do larger sensors have an enlargement factor? ;-)

BTW, when is RED's Monstro coming? After all, Sony is not delivering:

F23: 2/3 sensor, F35 35mm sensor, F65 35mm sensor ;-)

Didn't Canon invent the "Full frame" expression for upping their sales? Since medium format sensors are even larger ;)

How about expressing angles of view as angles? 35-mm equivalent focal lengths are for people who spent a long time using nothing but 35-mm photographic cameras.

@vicharris

Who's missing what point here?

In 40 years of film making I've never heard of a 5D equivalent. We say, "Gimme a 50" or more like "Let's try the Angie 50."

I'm saying that if you want us all to use some other lingo, then you may be right. Give us your ideas. They might just catch on.

(Does anybody else misunderstand me, or have we all been drinking, browsing other websites and watching TV simultaneously?)