Four Thirds Mirrorless Cameras (Page 5): FOV is in part determined by angle of view, but it’s also dependent on the distance to the subject. The AOV is constant but as your subject...

SuperflyTNT Loc: Manassas VA

Ysarex wrote:

Yikes! He comes up with the right answer in the en... (show quote)

FOV is in part determined by angle of view, but it’s also dependent on the distance to the subject. The AOV is constant but as your subject moves further away from the camera the FOV gets wider.

Ysarex Loc: St. Louis

SuperflyTNT wrote:

FOV is in part determined by angle of view, but it’s also dependent on the distance to the subject. The AOV is constant but as your subject moves further away from the camera the FOV gets wider.

Yes.

smf85 Loc: Freeport, IL

moonhawk wrote:

...If you compare the image circle of 50mm lensed from a FF Camera, an APS-C camera, and an m4/3 camera, the circles projected from the same distance will be three different sizes...

What is the same is the focal distance. 50mm is 50mm.

The image circle produced by a lens is used to calculate the focal length. As the size of the image circle changes so does the focal length, all other things remaining unchanged. So a 50mm FX lens will have a 46 deg. (Diag) field of view and cover the 36x24mm 35mm film frame/FX sensor size. If you use the lens with a different sensor size the focal length is unchanged. Sensor size doesn’t matter.

The image circles produced by a micro 4/3, APS-C, 1”, or APS-H designed lens (meaning the lens covers the smaller sensor size) would result in different focal lengths, all other things unchanged. Again it wouldn’t matter what sensor, their coverage and focal length would not change.

Mfr. list the focal lengths of their lenses as if they all covered the 36x24mm 35mm film frame/FX sensor size, which they don’t. So the real focal length of an APS-C lens is something other than what’s listed. So your 50mm DX lens is actually a 76mm lens. Stick it on-a full frame camera its still 76mm and still labeled 50mm. A 50mm FX lens is still a 50mm lens on a DX camera but it’s field of view has been cropped to that of a 76mm lens. Sensor size doesn’t matter; only the circle of light matters.

GoofyNewfie Loc: Kansas City

smf85 wrote:

The image circle produced by a lens is used to cal... (show quote)

From Nikon...(they know some things about lenses):
"It is not a measurement of the actual length of a lens, but a calculation of an optical distance from the point where light rays converge to form a sharp image of an object to the focal plane in the camera .

Image circle has nothing to do with it, only what size sensor or film a given lens can be used with.
Sensor size is not a factor in determining focal length of a lens.
It only determines the angle of view you'll get, assuming the image circle covers the sensor.

On a large format camera, a 90 mm lens would be a wide angle.
On a medium format it would be a "normal"
On a full- frame, it would be a short telephoto.
If you put those 90mm lenses made for large format, medium format or full-frame (35mm) on a full frame camera, you'd get the same image.

Actual focal length is marked on the lens.
A 50 mm lens on an APS-C camera is still ACTALLY 50mm.
It's "full-frame equivalent" is something longer, but the focal length does not change.

Other than for some dumbed-down cameras, lenses for are marked for their actual focal length, NOT their FF equivalent.

Ysarex Loc: St. Louis

smf85 wrote:

The image circle produced by a lens is used to calculate the focal length.

No. The focal length is the distance from the optical lens center (nodal point) to the film/sensor plane when the lens is focused. Traditionally lenses are inscribed with focal lengths when focused at infinity.

smf85 wrote:

As the size of the image circle changes so does the focal length, all other things remaining unchanged.

No. Image circle does not determine focal length.

smf85 wrote:

So a 50mm FX lens will have a 46 deg. (Diag) field of view

No. That would be angle of view

smf85 wrote:

and cover the 36x24mm 35mm film frame/FX sensor size. If you use the lens with a different sensor size the focal length is unchanged. Sensor size doesn’t matter.

The image circles produced by a micro 4/3, APS-C, 1”, or APS-H designed lens (meaning the lens covers the smaller sensor size) would result in different focal lengths, all other things unchanged.

No. Image circle does not determine focal length.

smf85 wrote:

Again it wouldn’t matter what sensor, their coverage and focal length would not change.

Mfr. list the focal lengths of their lenses as if they all covered the 36x24mm 35mm film frame/FX sensor size,

No. Manufacturers list actual lens focal lengths unless otherwise noted.

smf85 wrote:

which they don’t. So the real focal length of an APS-C lens is something other than what’s listed.

No. Unless the manufacturer actually states they are listing an equivalence value then the real focal length of an APS-C lens is the focal length listed.

smf85 wrote:

So your 50mm DX lens is actually a 76mm lens.

No. It's a 50mm lens.

smf85 wrote:

Stick it on-a full frame camera its still 76mm and still labeled 50mm.

No. The focal length listed is the actual focal length.

Joe

smf85 wrote:

A 50mm FX lens is still a 50mm lens on a DX camera but it’s field of view has been cropped to that of a 76mm lens. Sensor size doesn’t matter; only the circle of light matters.

SuperflyTNT Loc: Manassas VA

smf85 wrote:

The image circle produced by a lens is used to cal... (show quote)

You clearly don’t understand this at all.

wdross Loc: Castle Rock, Colorado

BebuLamar wrote:

I think the OP meant Micro four thirds because there is no mirrorless body I know of in Four thirds. As far as I know all the Four thirds cameras are DSLR.

You are correct. All 4/3rds cameras were DSLRs. But 4/3rds DSLRs were not around very long before it went to micro 4/3rds. 4/3rds DSLR started 1999 and 6 and a half years later was gone - replaced by micro 4/3rds mirrorless. As a result, when most people say "4/3rds", they really mean the present "micro 4/3rds", not the DSLR.

GoofyNewfie Loc: Kansas City

wdross wrote:

You are correct. All 4/3rds cameras were DSLRs. But 4/3rds DSLRs were not around very long before it went to micro 4/3rds. 4/3rds DSLR started 1999 and 6 and a half years later was gone - replaced by micro 4/3rds mirrorless. As a result, when most people say "4/3rds", they really mean the present "micro 4/3rds", not the DSLR.

A bit more info on the old 4/3rds format cameras:
https://www.dpreview.com/articles/9877975278/olympus-brings-down-the-curtain-on-the-four-thirds-system

I rented an Olympus E-1 for about a week when it came out.
Interesting camera, but image quality nowhere near what we have today.

smf85 Loc: Freeport, IL

SuperflyTNT wrote:

You clearly don’t understand this at all.

Actually I do, if there are errors in the description it’s due to my poor skill at writing not anything else.

This is a simple article on focal length calculation:
https://www.giangrandi.org/optics/focalcalc/focalcalc.shtml

SuperflyTNT Loc: Manassas VA

smf85 wrote:

Actually I do, if there are errors in the description it’s due to my poor skill at writing not anything else.

This is a simple article on focal length calculation:
https://www.giangrandi.org/optics/focalcalc/focalcalc.shtml

That article doesn’t appear to say what you think it does and while your writing skill may not be stellar it does not appear to be the reason your concepts are flawed. The image circle in no way determines the focal length. As a matter of fact, just about any focal length lens made for a particular sensor will have similar image circle sizes since those lenses are designed to cover a particular sensor. By your logic, a 50mm FX lens and a 50mm DX lens should have the same size image circle, yet you can use an FX lens on a DX camera, but not vice versa because the DX image circle won’t cover an FX sensor.

wdross Loc: Castle Rock, Colorado

TerryLA wrote:

I'm familiar with the full frame and the crop sensor camera but not the 4/3 camera. Would that be simular to the old medium fram cameras or is it totally different? And this a good starting point going into mirrorless if one can not afford the much higher prices of the full frame mirrorless cameras? Also what is a good model to go into if one were to purchase not being a professional photographer?

You have been given much information to gleen through. My suggestion is to go the the camera and examine both the mid cost Olympus and Panasonic cameras. Since you are not a total beginner, I don't think the lowest end cameras would bring the satisfaction you would be looking for. Although Olympus has come up quite a bit on the video end, Panasonic is still in the lead. I would look at making your system much more robust by looking at making the system weatherproof with weatherproof bodies and lenses. That way, if you are caught in the rain, or even deliberately shooting in the rain, it will not be a reason to run for cover. It will also help protect from many of the other elements like salt spray and dust. Lenses are usually smaller for the same angle of view.

I hope to pickup a 300 f4 Pro IS lens this week. Compared to a full frame 600 f4 IS (same angle of view), the lens is only 8.94" X 3.67" (FF is 15.2 X 5.5 and 17.6 X 6.6), 2.8 lbs. and 3.7 lbs w/tripod mount (FF is 6.7 and 6.8), and $2349 (FF is $12,267 and $12,999). One has to ask if the image quality difference is worth $10,000 more in cost. For most of us 4/3rds users, knowing the quality we get, the answer is very easily no.

Innershield1

Naptown Gaijin wrote:

I used to shoot Canon FF, then went to some compac... (show quote)

The Sony rx10m4 would be a good start