The Deliverator – Wannabee

So open minded, my thoughts fell out…

Fast Primes for Nikon Digital SLRs?

Posted by Deliverator on November 21st, 2006

While I have been greatly pleased with my new Nikon D80 Digital SLR itself, I have been somewhat less pleased with the lenses. My first issue goes to construction quality.

The 18-135mm “kit lens” that came with my D80 (upping the price by about $400 over a bare body) has a distinctly cheap feel to it. The bayonet mount is plastic, as is much of the body. It is good plastic, to be sure, but plastic none-the-less. I know there are constant arguments of “bounces vs dents” when it comes to debates of plastic vs metal construction. For overall body construction issues, I don’t feel really entitled to make an opinion, but I do know that the plastic bayonet mount is going to wear a lot faster from lens attachment/detachment than coated brass would. Additionally, the focus ring on this lens is small and very touchy. I have found using manual focus with this lens to be very trying. It is hard to get it focused just right and get it to actually stay that way. Autofocus is quick and accurate with this lens (due to the ultrasonic motor), but there are many situations in which you are going to have to rely on manual focus.

My second issue is the general lack of fast prime lenses that are well-matched to the smaller sensor of the Nikon DSLRs. Almost all the new DX series lenses in Nikon’s lineup are zoom lenses. The optical quality (if not the build quality) of zoom lenses has improved dramatically over the years due to better coatings, high refractive index glass, computer assisted design, and a host of other factors of which I am not aware. As a general rule, though, a lens targeted at a single focal length is going to be lighter, faster, cheaper to build and of better optical quality. Other optical considerations aside, the thing that frustrates me the most about zoom lenses is that they tend to be quite “slow.” My 18-135 ranges from f3.5 to 5.6, which is often too slow for using available light indoors. Even shooting at high iso speeds, I have found this lens difficult to use indoors without a flash. The results of on camera flash generally suck for any human subject, giving them that “stunned fish” look. I could buy an seperate flash for off-axis use to achieve better results, but why spend money on a flash when a better lens can do the job just as well. Not to mention, subjects tend to be less cooperative after having been hit in the face with a bright light more than a few times.

With my Konica T3 film SLR, I shot exclusively with fixed focal length lenses. My favorite lens is a 50mm “normal” lens which had an aperture that could be opened up all the way to F/1.4. A “normal” lens is, roughly, one that has the same field of view as the human eye. The wide aperture on this lens allows for enough light to hand hold shots in very dim conditions and lets one play around with a wide variety of depth of field effects in creating a composition. I really loved this lens and used it for the vast majority of shots I made with this camera over the years. So, why can’t I simply go out an buy a fast 50mm lens for my Nikon?

One of the advantages of the Nikon lens system is that Nikon has been making lenses for a very long time indeed. Nikon F-mount lenses goes back to 1959. You can use many of these older lenses on a modern DSLR, but often only in manual mode. The biggest disadvantage of using these older lenses is that due to the smaller size of Nikon’s CCD imaging sensor relative to a piece of 35mm film, there is a cropping/focal length multiplying factor of 1.5. In short, what this means is that a 50mm lens on a DSLR gives you the equivalent field of view of a 75mm on a 35mm lens. All lenses, in effect, become more “zoomy.” So, while you can certainly pick up a fast 50mm lens, on a DSLR it no longer presents a “normal” field of view. To get a “normal” field of view on a DSLR you need to go to something in the range of 28-35mm. Nikon has made a lot of lenses in this range of focal lengths over the years, so what is the problem?

While you can use many older lenses with modern DSLRs, most will not convey light metering information, so you have to use them in manual mode. This means guessing at proper exposure and shutter speeds, viewing the results and then adjusting accordingly. This is fine for some situations, but doesn’t make for quick, efficient shooting. Most older lenses are strictly manual focus. Nikon sells several 28 and 35mm lenses that are reasonably fast (f/2-f/2.8) and which also incorporate auto focus, but they use the old “electric screwdriver” means of changing the focus, which is noisy, slow and sometime inaccurate. Many of these lenses have to be manually switched back and forth between manual and autofocus modes. Most newer designed lenses which use internal, ultrasonic motors (rather than an electric screwdriver in the body) allow for instant switching between auto focus and manual focus, simply by twisting the focus ring. These ultrasonic motors are really nice, as it enables one to quickly auto focus and then touch up the focus if needed. The general feeling I get is that Nikon has really not updated its lens lineup to mesh well with digital bodies.

Although Nikon’s lens lineup has some holes in it, other companies are moving in to fill at least some of the voids. Sigma recently introduced a 30mm f/1.4 designed to be about “normal” on a DSLR’s smaller sensor size. Set beside a modern Nikon 35mm f/2, one can easily see the sheer light gathering potential of the Sigma. Another thing you may notice is the lack of an aperture ring on the Sigma. The Sigma optics are designed to throw light on just the smaller DSLR sensor. If you were able to use it at all with a film body, one would notice a lot of vignetting (light falloff) around the edges of the image. Because the Sigma lens is only going to be used on a DSLR, the aperture ring becomes unnecessary, as one can simply set the aperture with the thumb wheel on the DSLR body. The Sigma also incorporates an internal “hypersonic motor” allowing for fast, quite focusing and instant interruption for manual adjustment. In the half dozen reviews I read, I did see some complaints about the accuracy of the auto focus in certain situations, but the bulk of reviews had good things to say about this lens overall. Despite some reservations about off-brand lenses, I was disappointed enough in Nikon’s own offerings that I went ahead and placed an order for this lens at sigma4less. I will try to provide a reasonably amateurish review after it has arrived and I’ve had a chance to play around with it in a variety of scenarios.