Focal lengths Compact camera v SLR

leche solara

I have a Canon compact camera which claims to have a range of 28mm to 392mm (14X), when compared to 35mm film. I know (I think!) what this means. However when I take a photo at the wide end (no zooming) it is recorded as having been taken at 5mm, while at the extreme telephoto end its shown as 70mm (14X) Is the relationship between the 5mm and the 28mm the same idea as when saying that a 50mm lens on a cropped sensor SLR is equivalent to 80mm in 35mm terms. Is the crop factor on the compact therefore 28/5 i.e. 5.6.? Hope this makes sense

DaireQuinlan

Yes. /thread

The sensors on compacts are typicallyy the size of your thumbnail, so the same 'focal equivalence' thing comes into play.

Kintarō Hattori

Geeks, I have no idea how that whole focal length thing works. Gits.

charybdis

Kintarō Hattori wrote: »

Geeks, I have no idea how that whole focal length thing works. Gits.

Lenses (i.e.: bits of glass or similar non-opaque material shaped into an image-forming arrangement) have a property known as "focal length". That's pretty much it.

Zillah

charybdis wrote: »

Lenses (i.e.: bits of glass or similar non-opaque material shaped into an image-forming arrangement) have a property known as "focal length". That's pretty much it.

+Smaller numbers give a wider field of vision, bigger numbers are zoomed in. Normal human vision is the equivalent of about 50mm, for reference.

Kintarō Hattori

charybdis wrote: »

Lenses (i.e.: bits of glass or similar non-opaque material shaped into an image-forming arrangement) have a property known as "focal length". That's pretty much it.

Heh I know that but how they are different on full frame, cropped and then compacts is the confusing part.

Zillah

Kintarō Hattori wrote: »

Heh I know that but how they are different on full frame, cropped and then compacts is the confusing part.

Imagine projecting a movie onto a screen in the cinema, except the screen is much smaller than the film being projected, so the outer edge of the film is on the walls and shit.

The camera sensor is the screen and the camera lens is the projector. By cutting off the outer edge you increase the effective focal length (it looks more zoomed in). Full frame cameras (proffessional DLSRs) don't crop at all, APS-C sensors (consumer/prosumer DSLRs) crop a bit, and crappy tiny compact camera sensors crop a whole load.

I like metaphors.

woop

Zillah wrote: »

Imagine projecting a movie onto a screen in the cinema, except the screen is much smaller than the film being projected, so the outer edge of the film is on the walls and shit.

The camera sensor is the screen and the camera lens is the projector. By cutting off the outer edge you increase the effective focal length (it looks more zoomed in). Full frame cameras (proffessional DLSRs) don't crop at all, APS-C sensors (consumer/prosumer DSLRs) crop a bit, and crappy tiny compact camera sensors crop a whole load.

I like metaphors.

yeh thats basically it. The older 35mm slr are full frame and so are the likes of the 5d so this doesnt apply to them. Im very happy I have some knowledge of whats going on. There was a time when I wouldnt have had a clue what was going on

charybdis

Zillah wrote: »

+Smaller numbers give a wider field of vision, bigger numbers are zoomed in.

Only for a fixed format size.

Zillah wrote: »

Normal human vision is the equivalent of about 50mm, for reference.

Kinda. Talking about angle-of-view in terms of human vision is a bit misleading in that eyes don't have an angle-of-view in the strict sense and not everyone's eyes are the same. 50mm (which is often considered normal for the 135 film format) is not special in any way other than it happens to be normal for a popular format.

Kintarō Hattori wrote: »

Heh I know that but how they are different on full frame, cropped and then compacts is the confusing part.

The focal lengths aren't different, the angles-of-view are. Angle-of-view is determined by both the focal length of the lens used and the format size. Changing one and not changing the other will result in a different angle-of-view.

If you keep format size the same but change focal length, the angle-of-view changes (this is effectively what changing lenses on a camera or zooming a zoom is.)

If you keep focal length the same but change format size, the angle-of-view changes (this is effectively the same as using a lens of the same focal length on cameras with different sensor sizes).

Zillah wrote: »

Imagine projecting a movie onto a screen in the cinema, except the screen is much smaller than the film being projected, so the outer edge of the film is on the walls and shit.

The camera sensor is the screen and the camera lens is the projector. By cutting off the outer edge you increase the effective focal length (it looks more zoomed in). Full frame cameras (proffessional DLSRs) don't crop at all, APS-C sensors (consumer/prosumer DSLRs) crop a bit, and crappy tiny compact camera sensors crop a whole load.

I like metaphors.

Saying that full frame cameras "don't crop" is a bit misleading. Every format "crops", it's just that full frame is the same format size as 135 film which people like to express equivalent focal lengths in. Full frame sensors are "cropped" compared to medium format film, and every format is "cropped" relative to any format larger than itself.

Zillah

charybdis wrote: »

Saying that full frame cameras "don't crop" is a bit misleading. Every format "crops", it's just that full frame is the same format size as 135 film which people like to express equivalent focal lengths in. Full frame sensors are "cropped" compared to medium format film, and every format is "cropped" relative to any format larger than itself.

Is it not the case that the majority of lenses sold for DSLRs are designed for optimal use on full frame cameras? As in, anything larger would be redundant because you start just getting heavy vingetting (like if you use a DX lens on a D300). So when I say crop, I mean it chops off otherwise perfectly usable content.

charybdis

Zillah wrote: »

Is it not the case that the majority of lenses sold for DSLRs are designed for optimal use on full frame cameras? As in, anything larger would be redundant because you start just getting heavy vingetting (like if you use a DX lens on a D300). So when I say crop, I mean it chops off otherwise perfectly usable content.

A lot of lenses are designed so that the usable image circle they generate isn't much larger than the format they are intended for use with, but not all. Some lenses do generate a significantly larger image circle than the format they are intended for use with; tilt/shift lenses, for example.

All lenses "crop" in the context you're talking about unless the format completely contains the usable image circle generated by the lens.

Thecageyone

I often wonder do you guys ever think of anything else outside of the glass?

I used to think similar to OP, my old fuji was claiming all sorts of focal lenghs but read 6mm - 70mm [12x]

It did have "Super" macro though! Bonus .. if I'd known wtf that meant at the time ..

cnocbui

Focal length is a stupid metric and it should have been got rid of long ago. Angle of view is what should be used, then there wouldn't be any confusion or need for '35mm equivalance'. A 35mm film lens with a 45° angle of view is going to give tha same look as a 5mm focal length lens on a digital that also has a 45° field of view.

magicbastarder

cnocbui wrote: »

A 35mm film lens with a 45° angle of view is going to give tha same look as a 5mm focal length lens on a digital that also has a 45° field of view.

but the 35 mm lens may be used on a full frame camera or DX sensor, in the case of nikons. thus complicating things.
maybe they should use a metric of focal length/sensor size for cameras - so you get a zoom range listed as 0.5-7, for example. and print the sensor size of SLR cameras on the base, so the user can do the calculation themselves.

DaireQuinlan

cnocbui wrote: »

Focal length is a stupid metric and it should have been got rid of long ago. Angle of view is what should be used, then there wouldn't be any confusion or need for '35mm equivalance'. A 35mm film lens with a 45° angle of view is going to give tha same look as a 5mm focal length lens on a digital that also has a 45° field of view.

Except for the vastly greater DOF of course, just to be nit-picky.

I agree though, it's just that 35mm equivalence is how much of peoples thinking is wired in. I think it helps if you had some exposure to this sort of thing on a regular basis. I think of my 80mm on 6x6 as my normal lens, ditto the 300mm on my 8x10 stuff. It doesn't really take any mental gymnastics.
OTOH, it's not as though compact/bridge camera buyers are interested in anything other than ratios anyway. 20x superzoom OMG ! that's a what to what zoom ? Whatever ! 20x !!

jaybeeveedub

DaireQuinlan wrote: »

Yes. /thread

The sensors on compacts are typicallyy the size of your thumbnail, so the same 'focal equivalence' thing comes into play.

you must have tiny fingers!!

most canon compacts have a 6x4mm approx sensor I'd fit loads of them on my nail!!

well maybe not loads....