Does lens focal length refer to full frame sensors in common parlance?

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  • #169615

      Perhaps a no brainer question but as someone growing up using DSLR cameras with smaller sensors than full frame I was wondering what’s the “standard” when referring to focal lengths. In the podcast and even interviews Roger refers to different focal lengths and how they might affect the experience of the viewer. This is always referring to the focal length as experienced on a full frame sensor?

      On DSLR’s and even the Alexa Mini the sensors are Super 35 or smaller which comes with a crop factor so it doesn’t really translate. A 35mm lens on a Full Frame camera is around 27,5mm on a Super 35. So basically when you hear Roger or other cinematographers talking about lens choice, is it always referring to the lens in relation to a full frame camera?

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    • #169621

        Usually when a cinematographer names a focal length by number, it’s the actual focal length regardless of the format.


          I had that same question. So in general, are the cameras of most current films Roger has worked on been Super35 or Full frame Cinema cameras? That would give an idea of what field of view he’s referring to.


            @dmullenasc: Well, surely that depends on context. If a cinematographer says they prefer a 35mm for mid shots then that will look very differently on a Super 35 sensor as opposed to a Full Frame sensor.

            My assumption was that because crop factors are used to calculate what the comparative focal length would be on a Full Frame sensor that would be the standard. But I was unsure, that is why I was wondering.

            : Yeah. Empire of Light and 1917 was filmed on the Alexa Mini LF (Full frame). Blade Runner 2049 on the Alexa Mini (Super 35).


              This is a really good question!

              I would guess as the standard in cinema is still s35mm and stills’ “full frame” is more often thant not called “large format”, the standard would still be regarding s35 size.

              I guess the answer to this will differ much between stablished dp’s who’ve working since long before digital sensors and young dp’s that have been raised on the dslr revolution. The latter ones may use as reference more often than not to full frame the others not. Let’s take into account “full frame” only existed in cinema before the Canon 5d mkii as VistaVision, together with other large format standards such as 65mm, 70mm…


                “A 35mm lens on a Full Frame camera is around 27,5mm on a Super 35.”

                No, a 35mm lens on a Full Frame camera is 35mm on Super 35. The format doesn’t change the focal length of the lens.


                  The majority of cinema has been shot on standard 35mm for a century, not Full Frame. So there is no reason for filmmakers to always convert the focal lengths they are using to Full Frame equivalents in terms of field of view when discussing their movie. When we talk about Orson Welles’ use of the 24mm on “Citizen Kane” or the 18.5mm on “Touch of Evil”, we don’t convert those numbers to Full Frame equivalents.


                    To add another layer of interest I would suggest you stop thinking about focal lengths and Lenses, in my opinion it doesn’t help to understand how images are created. Here is an idea: Think more about distances, the distance camera to subject, the distance subject to background, the distance between subjects.

                    Al Duffield

                      Ah yes, this comes up rather frequently and poor David keeps getting stuck answering it.

                      I think what’s being confused here is field of view and focal length. focal length is an absolute and fixed attribute of a lens (assuming we’re talking about primes). Field of view is derived from focal length and sensor/film/gate dimensions.

                      From a practical standpoint, we could imagine using FOV instead of focal length during a shoot, but that would necessitate the AC’s determining and labelling each lens during prep based on the camera being used, and then the Cinematographer would then need to memorise the particular FOVs in order to get the right lens… all rather convoluted.

                      We could talk in full frame equivalents, but that too would require the AC’s to determine that, label up all the lenses and then refer to them as that equivalent focal length for the duration of the shoot.. again, a bit convoluted.

                      Instead, we are responsible for asking for the correct lens based on our knowledge of the resulting field of view for the camera we’re using. Sure Cinematographers are required to know the camera they’re using enough to know what a 35mm looks like on it, but that’s not much of a burden and it removes complications for the rest of the crew.

                      The Byre

                        A member of this forum put this very useful website together so that you can see how each lens works on each movie camera – there are even some of the more useful DSLRs in there!



                          Very interesting post.

                          Nice to see you back, we missed you!

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