What are the basic differences between using a lens specially designed for the digital SLRs and the 35mm lenses? I have a Nikon D70 and I've been using my lenses from my N70. I've been pleased with the results, but now I'm looking at purchasing a new zoom lens; is it important to get a digital lens or stick with the lenses I can use with both cameras? (I rarely use my N70 since I got the Digital.)

Hi! I've got a D70 also, and I also use lenses from my film cameras.

The DX lenses have a smaller rear lens element (I believe, correct me if I'm wrong!!) to match the smaller sensor on the digital camera. Some others here could give ya more info. Which zoom lenses were you looking at getting?

Hi! I've got a D70 also, and I also use lenses from my film cameras.

The DX lenses have a smaller rear lens element (I believe, correct me if I'm wrong!!) to match the smaller sensor on the digital camera. Some others here could give ya more info. Which zoom lenses were you looking at getting?

I think that DX lenses are likely to have a larger rear element that 24x36 lenses. One of the design goals of DX lenses is to have the light coming straight out of the rear of the lens so it hits the sensor face-on, even in the corners of the image. If the light is coming out at an angle it's possible that it doesn't hit the sensor sites in the corners because unlike film, each photosensitive site is in a little pit. This also means that the rear of the lens needs to have an excellent treatment against reflections to avoid light reflecting off the sensor, back onto the lens and back onto the sensor, making a ghost image.

Other design goals of DX lenses are:

- extremely high resolution. The sensor size is smaller than 24x36 and yet it needs to resolve the same image with just as much detail
- low chromatic aberration. Each pixel is the result of signals from 4 colour-sensitive photosites which are spread out horizontally rather than vertically as in a film. If a white line is being drawn by the lens as a rainbow of different colours then the result won't be a white line
- only cover the APS-sized sensor. This makes them smaller and easier to design and manufacture. If you put a DX lens on a film camera it will fit but you'll see that the corners of the image are black

Charles

Thanks for your help.