Angle of view with adapted lenses

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OzRay

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I know a 150mm focal length lens is always a 150mm focal length lens, but if the image circle of a Hasselblad 150mm is designed to cover a film area of 6cm x 6cm, then the field of view must be narrower than that of a 300mm in m4/3s terms.

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Ray
 

DavidB

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No, the field of view is determined by the combination of the sensor size and the focal length. The fact that this lens is projecting a huge image circle has no effect on the fact that the μ4/3 sensor is only looking at a tiny spot in the middle of it.

Incidentally, on a 6cmx6cm "sensor" the 150mm lens has a (diagonal) field of view equivalent to that of a 76mm lens on a "135 format" sensor, and thus for a Hasselblad it is a "short telephoto" lens. But put that glass over a tiny 4/3 sensor and the field of view is equivalent to that of a 300mm lens on a "135 format" sensor.
 

OzRay

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No, the field of view is determined by the combination of the sensor size and the focal length. The fact that this lens is projecting a huge image circle has no effect on the fact that the μ4/3 sensor is only looking at a tiny spot in the middle of it.
I understand this.

Incidentally, on a 6cmx6cm "sensor" the 150mm lens has a (diagonal) field of view equivalent to that of a 76mm lens on a "135 format" sensor, and thus for a Hasselblad it is a "short telephoto" lens. But put that glass over a tiny 4/3 sensor and the field of view is equivalent to that of a 300mm lens on a "135 format" sensor.
So, the Hasselblad 150mm is the like a 300mm on a 35mm camera, as a 150mm lens designed for 35mm is like a 300mm on m4/3s?

Cheers

Ray
 

RonSmith

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So, the Hasselblad 150mm is the like a 300mm on a 35mm camera, as a 150mm lens designed for 35mm is like a 300mm on m4/3s?


No, a 150mm lens is a 150mm lens, irrespective of the format it's designed for. Any 150mm lens attached to a :43: would have the field of view of a 300mm lens on a 35mm camera.
 

igi

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I think we really need to get used to using Angle of View instead of focal length when referring to the... err... the angle of view...

all these talks about focal length conversion could get people dizzy!:rofl:
 

OzRay

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No, a 150mm lens is a 150mm lens, irrespective of the format it's designed for.
It's insanely anal to always quote this when we all know that technically this is the case. We really need to chill out here. :horse:What we are talking about is the actual field of view/angle of view effect that a lens, made for a larger format, has on a smaller format. It's easier to talk in focal lengths (effective or otherwise) than writing out field of view/angle of view all the time, when we all know that's exactly what we mean. :dash2:

Looking at those photos of the Hasselblad lenses, it doesn't look like the adapters are much longer than for 35mm lenses, so that made me wonder whether the medium format lenses act as even longer focal length lenses than the usual 2x.:confused:

Cheers

Ray
 

RonSmith

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It's insanely anal to always quote this when we all know that technically this is the case. We really need to chill out here.

"Insanely anal?" Sorry. It's an occupational hazard. I'm a trial lawyer.

I guess it's better than being Anally Insane though.

I do agree, however, that we should speak only in terms of focal length, which is the one property that is constant.
 

arpoador

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Ray, Ron,

I think the key thing to remember here is that the focal length number (150mm) is a constant, but its effect will vary. Since we mostly think in terms of the 35mm full-frame film size as our reference, we've gotten used to multiplying by a factor of 2 (or 1.5 or 1.6 for CaNikon users) to get a sense of the field of view of the lens. For us, a 25mm lens is a normal lens (or, more relevantly, 20mm is barely wider than normal), where for a 35mm user 50mm is normal.

But Hasselblad and medium format users in general have long had the -opposite- problem. They've had to apply a factor (I don't recall the exact number) to understand their lenses in terms of the 35mm legacy standard. A 50mm lens (which is standard to 35mm and a telephoto lens to us) is actually a moderate wide angle lens on a Hasselblad. But if you're using it on µ43, however, that doesn't matter - it will still be a factor of 2 with respect to our baseline reference of the 35mm cameras.

That's why a 150mm 35-mm lens is 300mm equivalent to us (a longer telefoto than on 35mm). A 150mm Hasselblad lens is 300mm equivalent to us (a -much- longer telephoto than on the Hasselblad), and a 150mm PEN half-frame lens is a 300mm equivalent to us (exactly the same effect it had on the PEN).
 

cosinaphile

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there are 2 issues and 2 issues only ..... one is focal length, the other is the size of the image circle

when you speak of a 150mm lens,... be that for micro 4\3 ....35mm... medium format... or large format, the major and significant difference in those lenses is not angle of view it is the size of the image circle ,

the angle of view is what you end up with when a given image circle and a given sensor collide....

when you use a 150mm from another format camera on a micro 4\3 machine the image circle will either be too large, or less frequently, too small but the actual look the lens will produce as a 150 will be mostly the same , it may vignertte in the case c mount [at times] , or waste most of the image circle of a med format lens but it gonna look pretty close to what a micro 4\3 lens at 150 will look like

and a 150mm lens on an ep1 "acts" like a 300 on a 35mm this has to do with the sensor size relative to the image circle and nothing else

saying its a technicality does not change the fact that its a physical visual reality, people arent saying it to be cute
or beat a dead horse , if its a 150mm its gonna look like a 300 on micro 4\3 no matter where it came from
 

OzRay

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That's part of what I don't understand. For example, C mount lenses are designed so that the image circle covers the format and thus one would assume that all C mount lenses will not fully cover the m4/3s format, but this is not the case. I guess I'll remain perpetually confused.

Cheers

Ray
 

cosinaphile

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you are correct

many c mounts vignette badly , but think of it this way, if you would print a c mount transparency of say a 80 mm c mount lens with severe vignetting , print it vignetting and all
now put on 80mm hassy lens on , no vignetting , produce a hypothetical transparency
again
now the same for an 80 mm, 35 full frame lens another hypothetical transparencey

hypothetically you lay all the transparencies on top of each other and the objects are all the same size... figures and objects in the 3 shots would be about the same size

but the c mount vignettes !...but the part you see is the same as for the other lenses
the image circle was never meant for other formats .[some c mounts have larger image circles than others due to formula and design differences and work pretty well]

what about the hassy 80 mm well the micro 43 crop is using just what the other lenses use so the "angle of view on an ep1 is about the same
but consider the hassy again for a moment had you actually used it an a nedium format camera you would have seem most of the image circle thats alot of picture to the left and right of the m4\3 sensor ! its wider on a hassy because the huge image circle is used to it full benefit
 

jesse

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Lots of discussion !
Just imagine, 150mm on a 6x6 format film size, then crop the film size to the size of m4/3, finally you will get what you see in m4/3.
Focal length is never changed.
 

Brian S

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Maybe magnification would be a good descriptor to start using. A normal lens, magnification 1x, is 25mm on a 4/3rds camera. A 50mm lens is 2x on it. (Focal Length lens)/(Focal Length Normal) gives the magnification.

Anyway, I'm trying to decide what adapters to get. I have the M8 for the RF lenses. Have a Nikon DSLR for the F-Mount. Konica, Olympus OM, Retina S, M-42, Canon FL/FD, and some odds and ends, hmmm. Probably go with the Konica and Olympus for the EP-2.
 

Akashi

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Maybe magnification would be a good descriptor to start using. A normal lens, magnification 1x, is 25mm on a 4/3rds camera. A 50mm lens is 2x on it. (Focal Length lens)/(Focal Length Normal) gives the magnification.
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I am sorry that I need to revive this discussion again, but I dont get it. If I have a 50 mm full format lens and use it on my mu-4/3 I don´t get a 100 mm lens? I will only see what a 100 mm would see on a full format, which would be a lot less that the 50 mm. What about magnification? I thought that a 50 mm lens on a mu-4/3 would give me a 100 mm in magnification also..
 

OzRay

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I am sorry that I need to revive this discussion again, but I dont get it. If I have a 50 mm full format lens and use it on my mu-4/3 I don´t get a 100 mm lens? I will only see what a 100 mm would see on a full format, which would be a lot less that the 50 mm. What about magnification? I thought that a 50 mm lens on a mu-4/3 would give me a 100 mm in magnification also..
Technically, the focal length doesn't change. Because the m4/3s sensor is only taking the centre portion of the image circle formed by the lens, it gives the appearance of being a lens of twice the focal length. It would be the same as if you took the centre crop from a lens designed for 35mm, the apparent focal length has lengthened, because the field of view has narrowed.

The problem arises that when people say that the a 50mm lens on m4/3s is equivalent to a 100mm, the strictly technically minded people say no, that's not true. It's not true, but it makes it much easier for the non-technically minded to see in their minds eye what's happening. And because for all intents and purposes the visual results confirm that non-technical person's impression, we should accept that thinking about it this way is possibly the easiest way to avoid confusion and conflict.

Cheers

Ray
 

photoSmart42

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I am sorry that I need to revive this discussion again, but I dont get it. If I have a 50 mm full format lens and use it on my mu-4/3 I don´t get a 100 mm lens? I will only see what a 100 mm would see on a full format, which would be a lot less that the 50 mm. What about magnification? I thought that a 50 mm lens on a mu-4/3 would give me a 100 mm in magnification also..
Magnification is very different than field-of-view (FOV) and cropping! If you use a 50mm lens on your m4/3 camera you still have a 50mm lens (that's a lens attribute - has nothing to do with the camera you put it on), but you only see the center section of the image formed - thus a crop. You get the equivalent FOV of a 100mm lens on a FF sensor/film, but that's where the comparisons stop. It's still a 50mm lens, with the perspective of a 50mm lens.

Magnification is a relative measurement of the size of the image you see with respect to the size of your sensor. Same rules of cropping apply to magnification. Just because you see more or less of an object doesn't change its magnification. That only comes into play when you zoom in or out and change the relative size of the object.
 

Brian S

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Magnification is typically accepted as focal length of the lens in use divided by focal length of the "normal" lens for the format in use. The normal lens of the format in use is traditionally the diagonal of the image being collected. So on a 24x36 negative of a 35mm camera, the "normal" is typically considered to be a 45mm lens. Most cameras adopted 50mm as the normal for 35mm full-frame, a little easier for back-focus.

So if a 50mm lens is the norm, a 100mm lens gives 2x the magnification compared to a 50mm lens. Normal for u4/3rds is considered to be a 25mm lens. So a 100mm lens is a 4x magnification for a u4/3rds camera.
 
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