Need Help From Someone Smarter Than Me- M4/3 Crop Factor: I recently purchased a Olympus em5 mkll because I can't carry around my FF equipment anymore. I want to use my Nikon lenses...

mflowe Loc: Port Deposit, MD

I recently purchased a Olympus em5 mkll because I can't carry around my FF equipment anymore. I want to use my Nikon lenses until I can afford the M Zuiko goodies. I want to use one of the 0.71x focal Reducer Speed Booster. I have the FF math figured out. My 80-200 would be 114-284. I'm stumped trying to figure out the equivalent focal length of my 12-24 aps-c dx lens.
Any help would be greatly appreciated.

bleirer

Should be the same if I understand the question. The focal length doesn't change just because it is a dx

robertjerl Loc: Corona, California

mflowe wrote:

I recently purchased a Olympus em5 mkll because I can't carry around my FF equipment anymore. I want to use my Nikon lenses until I can afford the M Zuiko goodies. I want to use one of the 0.71x focal Reducer Speed Booster. I have the FF math figured out. My 80-200 would be 114-284. I'm stumped trying to figure out the equivalent focal length of my 12-24 aps-c dx lens.
Any help would be greatly appreciated.

Same math, focal length is the lens, nothing to do with the sensor it puts the image on. The image circle to cover the sensor is determined by the mount and distance of the sensor from the rear element of the lens. So with the reducer your are getting an angle of view of a 17-34.

TriX Loc: Raleigh, NC

If you mean that the DX lens is actually a 12-24mm lens (not 12-24 EQUIVALENT), then it would have an field of view equivalent to 24-48mm on a M43, and adding a .71x speed booster would yield 17-34mm equivalent.

mflowe Loc: Port Deposit, MD

TriX wrote:

If you mean that the DX lens is actually a 12-24mm lens (not 12-24 EQUIVALENT), then it would have an field of view equivalent to 24-48mm on a M43, and adding a .71x speed booster would yield 17-34mm equivalent.

Yes a 12-24 lens is always a 12-24 lens, but since it's made for a dx camera it projects a smaller image circle so is equivalent to a 18-24 on the dx camera. So I'm not understanding how it could be 24-48 on the micro 4/3. That would be the crop factor for a full frame lens.

mflowe Loc: Port Deposit, MD

robertjerl wrote:

Same math, focal length is the lens, nothing to do with the sensor it puts the image on. The image circle to cover the sensor is determined by the mount and distance of the sensor from the rear element of the lens. So with the reducer your are getting an angle of view of a 17-34.

Thanks for your response. I would appreciate if you could take the time to show me the math.

mflowe Loc: Port Deposit, MD

bleirer wrote:

Should be the same if I understand the question. The focal length doesn't change just because it is a dx

Thanks I understand the actual focal length doesn't change but the equivalent focallength does.

TriX Loc: Raleigh, NC

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mflowe wrote:

Yes a 12-24 lens is always a 12-24 lens, but since it's made for a dx camera it projects a smaller image circle so is equivalent to a 18-24 on the dx camera. So I'm not understanding how it could be 24-48 on the micro 4/3. That would be the crop factor for a full frame lens.

It doesn’t matter if it’s a FX, DX or M43, as you say it’s still a 12-24. It will have the field of view (or equivalent FL if you prefer) of 18-36 on a DX (1.5x for Nikon) and 24-48 on an M43. Then you multiply by the .71x of the speed booster and you get the EQUIVALENT FL of 17-34 on an M43. I get that it may seem counterintuitive or hard to wrap your head around

photogeneralist Loc: Lopez Island Washington State

Bier's statement is correct. The angle of included view changes but the focal length of the lens does not. For convenience we characterize the included angle of view as equivalent to that captured on a 35 mm negative by a lens of x mm focal length. The angle of view changes with sensor size but the focal length of the lens itself is not dependent on the sensor size behind it. DOF and f/stop are the same as they would be on a 35 mm format sensor/film frame.. Only the angle of view changes with sensor size. We need something to communicate the angle of view (AOV) so, for the sake of convenience, with a 1.5 crop sensor camera we compare the AOV to that of the old industry standard 35 mm film behind a lens of 1.5 tines the focal length of the lens of the crop sensor body.
Thus a 1.5 crop sensor behind a 100 mm lens will record a AOV eqquivalent to that of a 150 mm lens on a 35 mm film frame or a "full frame" camera body.
I hope that my explanation had been clear enough to be understood .

RichardTaylor Loc: Sydney, Australia

The crop factor for M4/3 is 2 (only the fov changes). I own a pair of Olympus em5 mkll bodies, however I only use Olympus lenses.

robertjerl Loc: Corona, California

mflowe wrote:

Yes a 12-24 lens is always a 12-24 lens, but since it's made for a dx camera it projects a smaller image circle so is equivalent to a 18-24 on the dx camera. So I'm not understanding how it could be 24-48 on the micro 4/3. That would be the crop factor for a full frame lens.

No, on a Nikon dx a 12-24 is the equivalent of an 18-36 and on your Olympus without the reducer it is a 24-48 equivalent but it is still 12-24 no matter what mount for what body it was made for. To calculate the equivalent for a crop factor the mount and body it is made for has nothing to do with it. Only the sensor's crop factor and the focal length are needed for the calculation.

So: a 12-24 is a 12-24 no matter what mount it is made for.
On FF it would be 12-24 aov if it had a FF mount
1.5 crop factor (Nikon) = 18-36 aov & on a Canon with a crop factor of 1.6 it would = 19-38 aov
2.0 crop factor (Olympus M4/3) = 24-48 aov
add the .71 reducer and = 17-34 aov

I rounded all numbers down.

mflowe Loc: Port Deposit, MD

robertjerl wrote:

No, on a Nikon dx a 12-24 is the equivalent of an ... (show quote)

I mistakenly typed 24 instead of 36. I understand and already know most of what you said considering dx an ff lenses and bodies. But I thought a say dx 12-24 lens projects a smaller image circle than a ff lens, that's why it would not be equivalent to a 12-24 on a ff camera. So how could the dx lens act the same as a ff lens on a micro 4/3 body?
Thanks for having the patience to deal with someone as dense as me. LOL

TriX Loc: Raleigh, NC

mflowe wrote:

I mistakenly typed 24 instead of 36. I understand and already know most of what you said considering dx an ff lenses and bodies. But I thought a say dx 12-24 lens projects a smaller image circle than a ff lens, that's why it would not be equivalent to a 12-24 on a ff camera. So how could the dx lens act the same as a ff lens on a micro 4/3 body?
Thanks for having the patience to deal with someone as dense as me. LOL

You are not dense, and you are correct - the projected image IS smaller, but the focal length lens equation is:
1/f = 1/Do + 1/Di, where f is the focal length of the lens, Do is the distance from the object to the lens and Di is the distance from the lens to the in-focus projected image, so the area of the projected image isn’t a factor in focal length calculation - only the field of view changes as you change formats. Make sense?

bleirer

Some interesting reading:

https://photographylife.com/what-is-crop-factor

https://photographylife.com/equivalent-focal-length-and-field-of-view

robertjerl Loc: Corona, California

mflowe wrote:

I mistakenly typed 24 instead of 36. I understand and already know most of what you said considering dx an ff lenses and bodies. But I thought a say dx 12-24 lens projects a smaller image circle than a ff lens, that's why it would not be equivalent to a 12-24 on a ff camera. So how could the dx lens act the same as a ff lens on a micro 4/3 body?
Thanks for having the patience to deal with someone as dense as me. LOL

What TriX said.

The image circle changes based on the distance of the rear lens element to the sensor. Now crop sensor lenses are often physically smaller so at the same distance as a FF lens they throw a smaller circle. But the image in that circle is the same size. Just not as wide an angle of view (field of view).

Oh, just to confuse things more on P&S, Super Zoom aka Bridge Cameras with a fixed lens some manufacturers do mark the apparent aov/fov lens equivalent rather than the actual focal length.