Are film lenses interchangeable to digital?

[Bushman]

Will lenses from a film SLR camera fit on a digital camera? I have not made the switch as yet, but I was cleaning out some stuff out of my mom's house and I found a practically unused Olympus OM-2 with a 50mm and a 35-200mm extra telephoto with a 2x adapter. The receipt was with it from 1988 and all the stuff was close to 1k back then. I know digital is the way to go for the future, but is a nice film camera a complete dinosaur now?

[Herne]

Yes and no!

Some cameras, like Canon, are using the same mount, so physically the same lens will fit. Its characteristics will change though, and depending on exactly which digital sensor one is using, there is generally a crop, or magnification factor. Typically 1,5/1.6 (though some very expensive digital SLRs are full frame), so a 50mm lens behaves like a 75mm full frame lens on a DSLR. And pro rata.

Nikon are even better - their lenses go back ages and still fit, though you do lose some functions.

Unfortunately, Olympus have changed to the 4/3rds mount, so an OM Zuiko will not physically fit on the DSLRs. There is however an adaptor, which is not expensive. The crop factor is 2x. So the 50mm behaves like a 100, a 500 behaves like a 1000 and pro rata.
Whether the adaptor give all the autofocus etc functions I am not sure - I have simply seen them advertised. Also it may upset the back focus, on mounts designed for the (short back focus) modern lenses, so one would want to look at the blurb carefully, before buying. (OTOH, by standing the lens out, it may specifically fix that problem!)

Crop factor. Only the apparent magnification of the lens is affected. F-stops, depth of field and hyperfocal distances are not affected. Unfortunately the modern sensor is so much much better than film, that any weaknesses in the older lenses quickly become apparent, though you can PS many of them out.

[Bushman]

Is that you Herne? I appreciate the information. I reads like I'd better just stick to film for now with that setup and when I go to digital, go all the way to digital. Thanks.

[Herne]

Yes - tis me.

I went all Canon, because I managed to sell my Olympus with its 2 kit lenses. And there are advantages in bigger sensors. However the 4/3rds mount does have some big advantages for wildlifers, simply because you get a 2:1 magnification over the orginal film setup.

So you can end up with a very long lens with proportionately a very big minimum f stop (critical at high magnifications), very cheaply.

So if you are looking to do that kind of thing at sensible money, you could buy an Olympus digital, or any other of the others that use the 4/3rds mount, and there are several that do, and use the adaptor and film Zuikos for specialised purposes. I think you'd find that using an adaptor as part of the standard kit, for everyday pix, though it might seem economic, but might quickly degenerate into a PITA.

So I wouldn't overlook what the 4/3rds system can do for you, despite its inherent technical disadvantages.

What are the disadvantages, because this is what you have to make your mind up.

Its all about sensor size. Crudely, a standard digital sensor is about 3/4 the area of a 35mm film frame. And a 4/3rds sensor is 1/2 the area. That's how you get the 1.5 and 2x magnification. They sit in the FOV and collect that amount of the total pic. Which places considerable strains on the resolving power of the LENS.

As a slight aside, older lenses may have a small problem with digital sensors. The emulsion side of a film is actually a pretty matt surface. Digital sensors are very shiny, and designed for digital lenses are very carefully coated, and sorted to maximise image contrast. Older film lenses very often did not have so much attention paid to that, because it wasn't necessary. Use them on digital sensors, and in some cases you can find a definite loss of contrast compared to hte same lens being used with film.

Next point is noise (digital of various sorts). Effectively the lower the gain you can run a sensor at the less the noise. Being less sensitive due to the lower gain, the less random photons are floating aobut to be picked up within the sensor. The energy arriving and being analysed by each photosite is dependent on its AREA. So for the same ASA/ISO, (sensitivity), inherently a larger sensor is running at a lower gain and is inherently less noisy. Which is why the more megapixels you go for, the tendency is to get more noise - each site is smaller, and while resolution increases, area decreases and you have to turn the wick up to get equal light response. The 4/3rds sensor is very small. Having said that, Olympus have done pretty well with noise control, especially at normal ISOs. However, at higher ISO settings, they are not as good as the Canons and Nikons of this world.

Can you live with that? Well that's something you have to decide for yourself.