crop factor

hitmanh · 07-08-2010

Can anyone tell what crop factors C mount and Oly Pen F lenses would have on a 4/3 camera?

Cheers

Matt

back alley · 07-08-2010

2x

.

ferider · 07-08-2010

Should be sqrt(2) = 1.4...

back alley · 07-08-2010

isn't the crop factor dependent on the cmaera and not the lens used?

the m4/3 have a crop factor of 2. a 20 mm lens is a 40 on the m/43, no?

rover · 07-08-2010

I would have voted for 2x too, but I have a feeling Roland is going to lay down some serious education on us.

In the end a 20 does have a 40 fov, so I am just laying back on this one to see how folks get to that answer.

hitmanh · 07-08-2010

Quote:

Originally Posted by back alley

isn't the crop factor dependent on the cmaera and not the lens used?

the m4/3 have a crop factor of 2. a 20 mm lens is a 40 on the m/43, no?

True for a lens designed to cover a 35mm film plane, which the C mount and Pen F lenses are not as far as I know. I'm wondering if they will have less of a crop factor as they're design to cover a smaller film plane.

Cheers

Matt

back alley · 07-08-2010

so, it was a trick question...

hitmanh · 07-08-2010

Quote:

Originally Posted by back alley

so, it was a trick question...

hehe, not really, I was just wondering if anyone had worked it out. I'm considering a 4/3 camera but the 2x crop put me off a little. If using Pen F or C mount can reduce that somewhat, I'd be happier.

ferider · 07-08-2010

Compared to full format, C mount and Oly Pen F are designed for a crop factor of 1.4. At least that's the image circle that they cover. For example, my 38mm Pen FT lens has roughly the FOV of a 50mm on full format (53 actually).

When using on u4/3 you reduce the image and decrease the FOV by another factor 1.4. So, in total, when compared to full frame, you have a factor 1.4 * 1.4 = 2.

So a Pen F 38mm lens on u4/3 will have the same FOV as a 76mm lens on full frame.

The advantage of C-mount lenses on u4/3 is that you can get very fast, relatively wide lenses.

Hope that makes sense,

Roland.

rover · 07-08-2010

38x2=76

Yup, same answer, different algebra

hitmanh · 07-08-2010

Quote:

Originally Posted by ferider

Compared to full format, C mount and Oly Pen F are designed for a crop factor of 1.4. At least that's the image circle that they cover. For example, my 38mm Pen FT lens has roughly the FOV of a 50mm on full format (53 actually).

When using on u4/3 you reduce the image and decrease the FOV by another factor 1.4. So, in total, when compared to full frame, you have a factor 1.4 * 1.4 = 2.

So a Pen F 38mm lens on u4/3 will have the same FOV as a 76mm lens on full frame.

The advantage of C-mount lenses on u4/3 is that you can get very fast, relatively wide lenses.

Hope that makes sense,

Roland.

Lovely, just what I wanted to know!

Thanks

Matt

back alley · 07-08-2010

headache....alert...

back alley · 07-08-2010

Quote:

Originally Posted by FrankS

Oh, measured with tactical lasers.

i have a piece of string...

ferider · 07-08-2010

Quote:

Originally Posted by back alley

i have a piece of string...

Can I use it as a garrote ?

hitmanh · 07-08-2010

Lol, sometimes I wish I kept my mouth shut ^^

Brian Sweeney · 07-08-2010

C-Mount lenses are made for different size sensors. The "closest" that you will find for u4/3rds camera are the lenses made for a 1" sensor. For that format, a 25mm lens is the normal for the C-Mount and is normal for the u4/3rds. I am waiting for a C-Mount adapter to try my Kowa 12.5mm F1.4 lens made for a 1" Vidicon.

As far as a lot of algebra and opinions, the term "close-enough" applies here.

You guys don't pronounce "LASERS" correctly, and do not have one that would have just melted the lens.

Brian Sweeney · 07-08-2010

This thread has gone off on a tangent that is far from the simple question asked by the OP.

A simple question was asked, and some simple answers were given.

If you want to get off on this overly-technical debate, take it to another thread.

This one is going to get turned into a simple answer to a simple question very soon.

gdi · 07-08-2010

Quote:

Originally Posted by Brian Sweeney

This thread has gone off on a tangent that is far from the simple question asked by the OP.

A simple question was asked, and some simple answers were given.

If you want to get off on this overly-technical debate, take it to another thread.

This one is going to get turned into a simple answer to a simple question very soon.

"the gad-fly cometh, it cometh from the"... Left Coast

Brian Sweeney · 07-08-2010

Okay. The OP asked a simple question, and had his thread Trolled.

Start this Tangential discussion elsewhere.

You made the OP wish he had not asked the question.

That is NOT what RFF is about.

This thread has been edited to filter out the tangential discussion, hopefully allow the answers to the question to come through, and not make anyone want to choke another RFF member with a garrote.