I get it now. Sorry for the stupidity on my part. I just had to visualize it as a sensor passing through the middle of the image circles of a 35mm and 645 format camera, respectively. The portion of the 645 circle will certainly be magnified. Indeed, my ratios apply for determining format equivalence, but not when mixing the formats. Often the simplest things escape us and confuse. Well, I suppose I have a pretty nice normal perspective piece of glass with my 35mm mamiya lens! I was hoping I could save money on a wide angle...damnit.
karl shah-jenner <shahjen@xxxxxxxxxxxx> wrote:
karl shah-jenner <shahjen@xxxxxxxxxxxx> wrote:
Trevor
: not trying to argue here, i'm just a little confused:
: the 1.5 factor comes into play because the size of the sensor is
different than the film plane on a 35mm camera, as the film plane on a
mamiya is different than a 35mm format camera.
the 1.5 is the multiplier applied to the *actual* focal length - in this
case 80mm - to give a 35mm equivalent.
what this means is that a 35mm lens (format unspecified) x 1.8 = 63mm
it's not actually a 63mm lens, but it will have the same field of view (NOT
anything to do with the imae circle size) as a 63mm would. ..on a 35mm
camera :)
now lets pretend we have three lenses of 35mm and these lenses came from a
16mm camera, a 35mm camera and a 645 camera. they all have different image
circle sizes and they all have different angles of view when shot using the
format they were designed for
35mm x 1.8 63mm
hmmm
that's pretty close to the 'normal' focal length for 35mm AND no surprise,
the real focal length (35mm) is close to the 'normal' focal length for the
16mm camera, to use the example above ;)
Essentially, the coverage and angle of view on a 80mm mamiya lens is vastly
different than the angle of view and coverage of an 80mm lens for a 35mm
format camera. On the 645 format, an 80mm lens is a normal perspective
lens, on a 35mm format an 80mm lens is a telephoto. Are you saying that
the 80mm mamiya lens on a dslr sensor is going to be 120mm?
yes! :)
My math is coming from frame diagonal ratios Further, how invalidated
would the focusing ring indicators be?
that depends on the film registration distance and this is different for
each camera/brand/format. Chances are if it's a well designed adapter then
they've taken that into account and you should maintain infinity focus..
t's OK Trevor - *equivalent focal lengths* are deceptive and confusing.
Best thing to do is to get used to the *actual* focal lengths and how they
relate to the various formats.
80mm =extreme wide angle (on 5x7 / 4x5)
80mm = moderae wide (on 6x9)
80mm ='normal (on 66)
80mm =moderate tele (on 35mm)
80mm =tele (on 16mm)
80mm = long tele (on 110)
it's all relative but the focal length remains the same ;)
k
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