Lens question: from film to digital

Bill2673

I did have (still have) a film Canon EOS 300.....the lens on this is EF 24-90.

I bought a Canon 50d body, stuck the old EF lens on it for the first few weeks.

Now I'm looking at buying a EF-S lens specifically for digital, probably a Canon 28-135, IS USM etc....

My question is this:

Taking the film lens and putting it on the digital camera magnifies the zoom, by i think 1.6....so it is the equivalent of a 38-144, or some such, on a digital camera.

Does the digital lens need to be magnified in the same way?

In other words, would the 28mm view on the EF-S lens used on the digital camera give me the same size of view as the 28mm view of the old EF lens on the old film camera?

Cheers,

Sorry if i haven't explained it well.

DaireQuinlan

In short, no. The focal length on the lens is its actual focal length. Because the sensor on the 50d is smaller than a piece of 35mm film by approximately 1.6, you'll get a correspondingly smaller field of view on the digital body as you would on the film body, so that 28->135 on your digital body will be the equivalent of a 45-> 216 on your film body.

Bill2673

DaireQuinlan wrote: »

In short, no. The focal length on the lens is its actual focal length. Because the sensor on the 50d is smaller than a piece of 35mm film by approximately 1.6, you'll get a correspondingly smaller field of view on the digital body as you would on the film body, so that 28->135 on your digital body will be the equivalent of a 45-> 216 on your film body.

Thanks, thats very helpful. So a 17-85 on a digital is probably the one I want to go for rather than 28-135.

Freddie59

Bill2673 wrote: »

Thanks, thats very helpful. So a 17-85 on a digital is probably the one I want to go for rather than 28-135.

I had the 17-85 IS lens for a year or so. Great lens, great quality.:)

JayEnnis

If you go for a full frame camera you won't have to worry about this. And if you have a collection of lenses already then its well worth the extra cost on the body.

Freddie59

JayEnnis wrote: »

If you go for a full frame camera you won't have to worry about this. And if you have a collection of lenses already then its well worth the extra cost on the body.

But he's bought a 50D.

Heebie

I definitely have to disagree with Daire Quinlan on this one.

I used to sell Canon/Nikon/Pentax/Tamron kit, and unless it says "effective focal length" somewhere instead of just having a set of numbers, then what it reads is it's actual focal-length, and the 1.6x multiplier for it's effective focal length still applies, so a 24-90 would effectively work as 38.4-144mm lens. (and thus NOT give you the same field of view as it would on a 35mm or "full-frame" body.)

There isn't really anything being "magnified".. it's that your lens projects a circle of light onto a plane parallel to the film/image sensor. The distance from the back of the lens to the film/image sensor is the same in a 35mm as it is in an APS-C digital or a "full-frame" digital.. so the circle is the same size.. but the sensor size is different, so it's only capturing light from a small area of the circle projected by the lens. (see illustration) Because you're taking a smaller section of the image, and generally looking at it at the same size screen, or making the same size print, it works out functionally like magnification. Hopefully this gives one an idea why the effects of a lens such as vignetting, and the distortions of fisheye lenses etc.. aren't as pronounced on an APS-C (1.6) or similar sized sensor.

Sizes in the illustration are not accurate..they're eyeballed.. and only relative to each other.

Bill2673 wrote: »

Taking the film lens and putting it on the digital camera magnifies the zoom, by i think 1.6....so it is the equivalent of a 38-144, or some such, on a digital camera.

Does the digital lens need to be magnified in the same way?

In other words, would the 28mm view on the EF-S lens used on the digital camera give me the same size of view as the 28mm view of the old EF lens on the old film camera?

Cheers,

Sorry if i haven't explained it well.

DaireQuinlan

Heebie wrote: »

I definitely have to disagree with Daire Quinlan on this one.

I used to sell Canon/Nikon/Pentax/Tamron kit, and unless it says "effective focal length" somewhere instead of just having a set of numbers, then what it reads is it's actual focal-length, and the 1.6x multiplier for it's effective focal length still applies, so a 24-90 would effectively work as 38.4-144mm lens. (and thus NOT give you the same field of view as it would on a 35mm or "full-frame" body.)

ehh ... I think that's almost exactly what I DID say !

TinyExplosions

DaireQuinlan wrote: »

ehh ... I think that's almost exactly what I DID say !

That's what I thought too!

Heebie

I just re-read your original post.. did I really misread it that completely before? =O

DaireQuinlan wrote: »

ehh ... I think that's almost exactly what I DID say !