blackest Loc: Ireland

But there is a slightly confusing issue lets say we take a picture of somebodys head with a full frame and from top of his head takes the whole height of the frame. If you then take that lens and attach it to a m43 lens (4 m43 sensors are about the same area total as a full frame sensor) because the sensor is half the height if you stand in the same spot and take the same shot you only get half the head in the frame. The image circle hasn't changed size but there is half as much sensor height wise. So you back away from the subject till all the head fits on the smaller sensor.

Because now you are around twice the subject camera distance away. The depth of field has changed. To get the same depth of field as on the full frame. You need to open up wider about a stop on aps-c and 2 stops on m43. This may be ok if the lens was at f4 and can open to f2 but if it was f2 then you would need to go to f1 for the same/ similar depth of field. Where do you get such a lens?

If the light level hasn't changed then the shutter speed will need to be 2 stops faster too. E.g if the ff used 1/250 then the m43 will need to use 1/1000th so with less motion blur the image may still look different.

camerapapi Loc: Miami, Fl.

And the answer continues to be YES. Using a crop sensor the focal length of the lens has to be multiplied by the crop factor. In the case of the FX lens only the center of the lens is used.

jerryc41 Loc: Catskill Mts of NY

Play around with these lens simulators, and see for yourself.

http://imaging.nikon.com/lineup/lens/simulator/
http://www.dpreview.com/galleries/9059751105/photos/2518330/olympus-zuiko-lens-field-of-view-comparison

alandg46 Loc: Boerne, Texas

The key word is crop.

LFingar Loc: Claverack, NY

Yes. As you probably know, the focal length does not change no matter what camera you use the lens on. Crop factor does only one thing: It compares the view characteristics of two different size sensors. There are a variety of crop factors, depending on what sensors are being compared. You are NOT comparing lenses. You are comparing sensors, so the type of lens being used is immaterial other then it's focal length serving as a point of comparison.

Edia Loc: Central New Jersey

The difference between an FX and DX lens has nothing to do with the focal length. The periphery of an FX lens must have less distortion than a DX lens since the FX sensor has more area exposed. That is why FX lenses are more expensive than DX lenses.

Architect1776 Loc: In my mind

You do not ever need to multiply or divide or perform calculus. The "Crop Factor" is a reference relative to the 35mm format that was prevalent prior to digital cameras. To go to extremes a 100mm lens on an 8x10 camera is an extreme wide angle (I don't know the factor so look it up) lens so there is a huge crop factor of say 15 compared to the APSC format.
So the "Crop" is just relative to some other format. 100mm is always 100mm regardless of the format.

JaiGieEse Loc: Foxworth, MS

Why do you all insist in wasting time in this manner? The process is simple. Forget the mathematics. Raise the camera to your eye. Engage metering/auto-focus or use manual focus. Check the settings in your viewfinder to ensure that shutter speed/aperture are set as you wish, then compose the image in your VF and depress the shutter. Move on to the next shot. Let someone else worry about how your sensor/lens combo affects focal length, field of view or whatever. If what you see in the VF suits you, TAKE THE BLASTED PICTURE.

zigipha Loc: north nj

It has nothing to do with the % of the lens that falls onto the sensor. It has to do with the additional magnification needed to bring a crop sensor image to the same size (8 x 10 example) vs a ff sensor

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

What additional magnification? If an image comes from a 20 Mpixel sensor, regardless of the sensor size surely it will have the same magnification to produce an 8 x 10 image?

There a clearly some advantages of larger sensors, but is that the issue here?

amfoto1 Loc: San Jose, Calif. USA

You actually don't need to do any math at al..., unless you are using both camera formats together or changing formats for some reason.

100mm is 100mm... regardless of what camera it's used upon.

The sensor size (or film frame area) determines how that 100mm lens "behaves"...

- On a large format 4x5" film camera, 100mm is a very wide angle
- On a medium format 6x7cm film camera, 100mm is a standard lens.
- On a "full frame" digital or 35mm film camera, 100mm is a short telephoto.
- On an APS-C film camera or DSLR, 100mm is a moderate telephoto
- On a point-n-shoot digital with a tiny sensor, 100mm would be a super telephoto.

If you only ever use an APS-C camera, none of this really matters. You can buy either type of 100mm - "crop only" or "full frame-capable" - and it will behave as the same 100mm moderate telephoto on your camera.

A common difference is that "crop only" lenses can be smaller, lighter and often less expensive than "full frame" lenses. This is because the crop only lens doesn't need to produce as large an image circle in order to cover the smaller size sensor. Most APS-C cameras can use both. Full frame cameras are limited to full frame-capable lenses only, and those lenses tend to be larger, heavier and more expensive.

amfoto1 Loc: San Jose, Calif. USA

Assuming no cropping of the image in either case...

If you make an 8x12 from a "full frame" image, you are enlarging the image slightly more than 8X.

But if you make the same 8x12 from an APS-C capture, you're enlarging that image approx. 13X.

Black Bart Loc: Indiana

If you check a DOF calculator it shows DOF will change with crop camera over a full frame.

blackest Loc: Ireland

The crop factor on larger than 35mm is fractional, I think medium format digital it is about 0.7 so a 100mm lens would effectively be the fov of a 70mm lens on a medium format camera. On an 8 by 10 much shorter. essentially the larger the sensor or film size the easier it is to control depth of field with slower lenses. Diffraction effects are less obvious too as you have less enlargement of the recorded image. Kind of counter intuitive but you need better quality lenses on a small format camera than on a larger one.

Trabor

:thumbup: