The final sensor crop thread

-Tom-

-Tom-

Active member
After being told that 11mm lens on GH2 would act like an 11mm lens, I realized I still havent figured out the math behind the glass and sensors.

First of all, whats up with GH2 sensor size? Some places online claim 18.89 x 14.48 mm (source), others claim 17.3 x 13.0 mm. How is it unknown, is it a Panasonic's best kept secret?

Comparing the GH2 for "movie looks" mandates that we take Super 35 film size into account. OK - whats the size of that? Wiki says "If using 4-perf, the Super 35 camera aperture is 24.89 mm × 18.66 mm" - whats a 4-perf? Are these sizes final, super 35 = 24,89x18,66 or are there more confused exceptions to those numbers also? And what about the 2 reported GH2 sensor sizes? Which one is correct?

Finally, calculating field (some say "angle" is the correct term) of view for GH2 and 3rd party lenses is something I cant understand. Apparently it differs from film and pics (I guess this statement is valid if we presume that the GH2 video is always shot in 1080p and the pics are taken in 4:3 or 3:2...I take mine in 16:9 aspect but thats just me) - so GH2 photographers would need to use another equations - which ones?

From what sensor size should they start?

Lumix 7-14 offers crazy wide angles for the GH2 and similar m43 friends. Lets say we put those lenses via some kind of adapter on to 5DMK2...what kind of "35mm numbers" FOV are we talking about at the wide end?

Also, how can some 3rd party 11mm lens screwed on GH2 be claimed as 11mm? The sensor will get the light from the center of the lens (so to speak) and will crop the lens (ok no vignetting, I guess thats a plus) - so why even bother getting that glass when you already have that (or very very similar) FOV with stock GH2 lens, 42's or 140.

Please help and sorry for bringing up these beaten up subjects :D
 
-Tom- said:
They claim 15mm lens equals 180 degree angle of view...
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A 15mm lens does not equal 180 degree angle of view. A 15mm lens equals = a 15mm lens. The angle of view is determined by how big the sensor is that the lens is in front of. On a huge sensor, a 15mm lens will be a wide angle lens. On a tiny sensor, a 15mm lens will be a telephoto.


So what kind of image would 7mm lens produce?
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Depends on what kind of sensor it's pointed towards. On a GH2, it will provide a very wide field of view, wider than a 15mm lens on a "full frame" camera.

Or even my 14-140 lens on wide end?
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Again, depends on how big the sensor is behind it. Presuming that it's matched to the same sensor as you used the 7mm lens, then a 14mm lens will be twice as telephoto. In terms of "full frame" equivalent, it'll be about the same as a 28mm lens on a "full frame" camera.

As for sensor size, the m43 standard is 17.3 x 13.0. However, not every camera uses that. An AF100 is 17.8 x 10mm. The GH2 is 18.9 x 10.6. The GH3 is 17.3 x 13.

And why does Tamron's tool say that 10mm lens will be good for 106 degree AOV?
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Again, depends on what sensor it's connected to.

If you put that Tamron on a GH2, and set it to 10mm, you would get the identical same field of view as if you took the Lumix 7-14 and zoomed it to 10mm. 10mm = 10mm = 10mm = 10mm.

If you put a 50mm lens from a 5D onto a GH2, and you took your 14-140 and zoomed it to 50mm, both of them will deliver an identical field of view. 50mm = 50mm.

If you put a 50mm on a 5D, and zoomed your 14-140 into 50mm and put that on a GH2, NOW is when you'll have a different field of view, because the sensor size is different. The field of view is not different because the lens was designed for a different sensor, the field of view on the same sensor will always be the same regardless of what size the lens was designed for. But when you have two different sensor sizes, they will see different areas of the image that the lens projects.
 
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