Silverrails

👍👍👍, Very well explained, a important determining factor here is the difference in Sensor size between a DX- Crop-Sensor Camera and a FX- Full Fame Camera.

GoofyNewfie Loc: Kansas City

Get your terms right.
DSLR’s (digital single lens reflex) are a camera design and
come in several formats:
APS-C, FF (like 35mm film) and medium format.
Mirrorless interchangable lens cameras (MILC) add micro 4/3rds format to that list of available formats.

BebuLamar

The DOF would be different for the same aperture. The reason is that although the size of the circle of confusion is the same in both case the acceptable size of the circle is larger for the 8x10 because you don't need to enlarge as much when making print of the same size. There is no compression effect of longer focal length. Longer focal length doesn't have the compression effect. The compression effect depending on the camera to subject distance. With narrower angle of view we tend to stay further away from the subject thus we associate the effect with long focal length.

GoofyNewfie Loc: Kansas City

Yes, it was a short-sighted comment making it even more confusing for anyone who doesn’t know they mean the “equivalent of a 150mm lens on a full-frame camera.”

FTn

Shooting with a big lens does not in any way mean the photographer has a big brain.

- FTn

frankraney Loc: Clovis, Ca.

that's what I have always said Bill. Aim, frame and shoot.

cjc2 Loc: Hellertown PA

ABSOLUTELY INCORRECT!!!!!!!!!!!!!!!!!!!!!

Delderby Loc: Derby UK

Consider yourself to have received a pat on the head and a gold star. Happy now?

DSLR was the term originally used for cameras with an APS-C size sensor (before FFs were manufactured).
FF was the term used for DSLR style cameras with a similar sized sensor to 35mm film.
MILC is a goofy term for the above with EVFs, the first of which were MFTs (or M43, for the goofy newfies)

So we should have EVFF, OVFF, EVSLR, OVSLR, MFT, BRIDGE, COMPACT, SMART PHONE.

When reflex cameras stop being manufactured in the next year or so I feel sure that the terminology will become simpler and less confusing.

MT Shooter Loc: Montana

There's so much wrong with this post I could write a book!
But I have neither the time nor inclination so I won't.

Delderby Loc: Derby UK

I would be genuinely glad if you could enlighten me.

fosis Loc: Pittsburgh, PA

Two concepts to be understood:
1. A 100 mm lens, regardless of DX or FX, will deliver the same image size to the film plane or the light sensitive imaging sensor. It is the size of the sensor that "crops" the image to appear like 150mm on a DX.
2. A 100mm DX lens is not made to throw its image in a circle that is large enough to cover a 24 x 36mm full frame sensor or film. A 100mm FX lens will throw its image over that larger area.
So if you don't mind a little extra light thrown back into the inside of the camera, you can use an FX 100mm lens on a DX body and get the same "150mm" image on the smaller sensor. And you can use that lens as a 100mm lens on an FX body.

sirvive Loc: South Louisiana

As already stated, the answer to the original OP’s question is yes; mounting 100mm FX lens on a DX camera will give you the equivalent angle of view of a 150mm lens.

Some very good explanations have been given but I agree with KISS and “almost gives me a headache”. I may be producing yet another kind of headache
My attempt at simplifying …

Focal length equivalents for DX (APS-C) and FX (full frame) lenses … “crop factor”

ANY FX or DX lens on a DX sensor camera
Equivalent Focal Length = 1.5 X (actual marked focal length). Example: 100mm lens = 150mm equiv. = 1.6 X (actual marked FL for Canon) Example: 100mm lens = 160mm

ANY FX or DX lens on an FX sensor camera, no crop factor
Equivalent Focal Length = actual focal length. Example: 100mm lens = 100mm

ANY lens on a 4/3 sensor camera (micro in micro four thirds, only refers to the lens mount)
Equivalent Focal Length = 2 X (actual marked FL). Example: 100mm lens = 200mm equiv.

Other sensor (and film) sizes have lens view equivalents that can be compared to “full frame” sensors, according to their relative sizes.

So… to judge your field of view, equivalent angle of view, lens does not change...

if using a DX camera, multiply ALL lens FLs by 1.5
If using an FX camera, lens view is what is marked
If using Micro 4/3 cameras, multiply all lens FLs by 2

rikhar Loc: Ct. shoreline

Thank you for your reply Kozan, but that does not answer my question
rick

Delderby Loc: Derby UK

Yes am I right in thinking that with M43 the lens diameter can also be smaller because of the format (as the shape becomes more square it better fits to a circle)?

R.G. Loc: Scotland

Further to what myself and others have said, when discussing or asking about these matters, everybody involved should be clear whether they're referring to actual focal length (as stated on the lens) or full frame equivalent (usually abbreviated to "FF equiv." or some such).

Focal length is not directly related to angle of view because for any given focal length, angle of view changes as the sensor size changes.

But for any given sensor size, angle of view is directly related to focal length - provided the image produced by the lens is big enough to completely cover the sensor (this is why FX cameras have to be used in crop mode when using DX lenses).