If you see -o- symbol on your camera, that's focal plane mark of the camera.kcuf2 said:yes u are right in a sense, the physical length of the lens is roughly equal to the focal length..
but the focal length should be measure from the tip of the lens to the "focal plane" of ur camera. To know where's the focal plane, it is inside ur manual if u are using nikon camera like D50 and D70s.
student said:Not talking about 35 mm, but whether a lens's physical length is nearly its focal length.
Pardon the quality of the picture. Here are two lenses.
The longer one is a 210 mm lens for the Contax 645.
The shorter one is a 229 mm lens for a 4x5 camera.
Let us say that there is "no difference" between the 229 and 210. The image characteristic (such as depth of field for a given aperture) of these two lenses should be the same.
But it is clear that lenses with the "same" focal length do not have to have the same physical length.
student said:Not talking about 35 mm, but whether a lens's physical length is nearly its focal length.
Pardon the quality of the picture. Here are two lenses.
The longer one is a 210 mm lens for the Contax 645.
The shorter one is a 229 mm lens for a 4x5 camera.
Let us say that there is "no difference" between the 229 and 210. The image characteristic (such as depth of field for a given aperture) of these two lenses should be the same.
But it is clear that lenses with the "same" focal length do not have to have the same physical length.
Hi,student said:Not talking about 35 mm, but whether a lens's physical length is nearly its focal length.
Pardon the quality of the picture. Here are two lenses.
The longer one is a 210 mm lens for the Contax 645.
The shorter one is a 229 mm lens for a 4x5 camera.
Let us say that there is "no difference" between the 229 and 210. The image characteristic (such as depth of field for a given aperture) of these two lenses should be the same.
But it is clear that lenses with the "same" focal length do not have to have the same physical length.
weixing said:Hi,
I think that may be because the 4x5 camera got a focal plane far more behind compare to a SLR camera.
Anyway, it'll only a useful and valid comparison when you compare only between SLR lenses and not compare a SLR lenses and a 4x5 lenses.... it like compare between apple and watermelon to see which one got more juices.
By the way, those mirror lenses will have a much shorter physical length than it focal length.
Have a nice day.
No. Not necessarily so. Nowadays, lenses are so complex. One good counter example is the use of a teleconverter. Just a short section but it can turn a 200mm lens into 400mm.Splutter said:From what I know, the physical length has to be at least equal to the focal length. The diameter is also at least equal to the (focal length) / (min aperture size).
I never use a 4x5 camera before... (I'm still a newbie in photography). But just wonder does the distance between the lens and the focal plane of different focal length lens differ by much when focus on a same object at same distance. My guess is that part of the camera body itself may act as an extension of the lens, so althought the phyiscal length is similar, the distance between the lens and focal plance may be different... and of course I may be wrong also, since there are various ways of increasing focal length without increase the physical length.student said:Your point that we should not compare 35 mm to 4x5 is valid.
I may do some studies on 35 mm lenses. It may take some time, but meanwhile I had taken more images of different 4x5 lenses.
Left: Nikkor 300mm
Right: Nikkor 150mm
Left: Nikkor 150mm
Rght: Linhof 135mm
Hi Is,lsisaxon said:No. Not necessarily so. Nowadays, lenses are so complex. One good counter example is the use of a teleconverter. Just a short section but it can turn a 200mm lens into 400mm.
Depend... ha ha ha Should be same length if from same manufacturer, but 300mm f2.8 should be bigger in diameter than 300mm f4.+evenstar said:300mm 2.8 vs 300 f4...which one is longer?