Digital lens + non digital SLR

I've heard buying a digital lens for an old (non-digital) SLR is a waste

because you miss out on certain aspects of the lens. Will an AF lens still

automatically focus on a non-digital SLR?

 

I guess my question is, does the lens itself have a little battery and power

unit or does it rely on the camera for this.

 

Thanks.

There really is no such thing as a "digital lens" although some manufacturers use that terminology. Exactly which lens do you have in mind?

 

Nikon AF lenses will work the same way (e.g. AF) on DSLRs as film SLRs. The main issue is that DX lenses don't cover the entire 35mm film frame (or FX frame).

I see, so although an AF lens will still automatically focus on a film SLR, the manufacturer specs (ie. f-stop and focal length) will not be entirely accurate for FX?

 

I've just been searching around for a wide angle and I've come across various DX lenses that I've been disregarding. I don't have a particular one in mind.

Other than the difference in coverage Shun mentioned, about the only difference some "digital" lenses might offer is improved multi-coating on the rear optical group. This design evolved to cope with the highly reflective surfaces of digital sensors.

 

So, assuming the "digital" lens will fully cover the 35mm film format, no harm will be done by using such a lens on a film SLR. Any optical improvements for digital sensors will also benefit film.

 

But be sure the lens is fully compatible. Many "digital" lenses lack an aperture control ring and some older cameras cannot function properly with such lenses. Nikon uses the "G" designation to identify lenses lacking an aperture ring. With third party lenses you'll need to check carefully.

No, that's not it. The specs are accurate. An 18-70mm f3.5-4.5 will behave the same in

terms of focal length and aperture on both cameras, however, the image circle is smaller,

because it is designed for a sensor that is smaller than full-frame.

 

As far as Autofocus compatibility goes, it depends on what camera you have. What camera do

you have and what lenses are you looking for?

 

If you are shooting full-frame film, do not buy a DX lens. It will not give you what you want.

It might depend on which DSLR you are considering. D40 and D40x require lenses with internal AF motors (Nikkors call these AFS lenses, Sigma calls these HSM lenses, and now Tamron has an AF 70-300mm f/4-5.6 Di LD Macro Model A17NII with an internal AF motor). Lenses without AF motors will still work on a D40 or D40x, but they will not AF. The lenses derive power for their internal motors from the camera body and require no batteries.

 

Regarding "equivalent" focal lengths and apertures, just ignore all of that for now. A 50mm f/1.8 lens is the same focal length and aperture regardless of whether it is used on a film, FX, or DX camera. The only thing that changes when using it on a DX camera is its image circle, which is cropped. It is too technical to go into the effects on DOF of cropping the image circle here, just realize that to get the same FOV (field of view) a 50mm lens provides on a film or FX camera you would need to use something like a 30mm or 35mm lens on a DX camera.

"I've just been searching around for a wide angle and I've come across various DX lenses that I've been disregarding."

 

If you are still looking for a wide angle lens for your Nikkormat (http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00O7S2), then no lens you buy will autofocus on that camera. Autofocus is camera driven, not lens driven.

 

As to DX lenses, they are all G lenses (no aperture ring), and are essentially useless on a Nikkormat. Not to mention that ANY DX zoom lens will severely vignette at the wide angle setting because of the smaller projected image circle when using it on a film camera. That sort of defeats the purpose of using it in the first place, making it 100% useless. Continue to disregard them.

 

How wide is "wide angle"? As noted by many posters in the other thread, there are many options. For 24mm and above, there are many bargain non-AI Nikkors available in 24mm, 28mm and 35mm focal lengths.

I'm currently using a Sigma tele-macro 18-90 (?) on a Nikon N75 film SLR and it works fine. The autofocusing is lightning fast and accurate, and I think the Nikon is more to praise for that than the lens. I think I have a digital lens cause I do see a capital "D" in the lens model name. The pictures I have taken so far have come out looking fantastic. I do have to keep the F-stop set to highest value, F22, in order for the Program mode to work right on the Nikon N75. When the aperture ring slips off F22 to something less, the Nikon starts giving me a nasty little "E" in the LCD screen, and it refuses to take a picture, till I click it back to F22. So, at least this combination works OK for me, an amateur & beginner. A pro, of course, would be much more discriminating & demanding. My lens does not have a battery in it, but does have an internal motor, which, apparently is powered & finely controlled by the N75. Like I say, the auto-focusing with this combo is fast, decisive, and very accurate, at least in Program mode. My first sample picture was to focus on a Garden Spider hanging in the middle of his web, at a distance of about 1 meter. The lens response was almost instantaneous, and there was no evidence of any "fishing" by the camera to get the right focus.

Thanks Michael, I think you gave me the answer I was looking for. I'm not planning on buying a DSLR, I'm just looking for a wide angle lens (28mm or maybe 24mm) for my current Nikkormat. I'll check out the link.

Nevermind, I see now it's my other post. So what you're saying is that an AF lens will not auto focus if it's on my old Nikkormat?

Yes. An autofocus lens will only autofocus on an autofocus camera. You can use an autofocus lens on a Nikkormat, but you would have to focus it manually.

Shun, Lex:

Digital cameras have one or more glass plates covering the sensor. The total thickness of the glass is on the order of 2mm. Something that very few people appreciate is that this sensor glass will introduce enough astigmatism to degrade the performance of better film lenses used wider than ~f/8. A properly designed digital lens must accordingly be designed to compensate for the effects of the sensor glass.