All are welcome to add to this field test because this lens has only been out for a short time. My initial impression; it is a heavy lens and weighs almost as much as my 300 Takumar! It is also very large, about the same as the 165mm. The lens has no DOF scale, presumably because it is impracticle to fit the various scales on the barrel. My suggestion to Pentax would be put one on the barrel for the 55mm focal length only and for every other focal length, put hyperfocal marks for f/32 only. Instead they put two infra red marks on the barrel. Anyone out there use infra red film? I don't know of anyone. Those two marks have little use. Focusing is very smooth but zooming takes more effort to move the ring. Build quality is really good with the fit and feel being excellent. The lens hood comes with this lens and it fits tightly (almost too tight). The diaphragm is an eight blade type but I wish it were ten or 12 for a rounder opening. For a zoom lens, it is surprisingly sharp. My first impression is that it's sharper wide open than the 105mm at f/2.4. I tried some macro shots with it and I could see excellent detail off axis at all f-stops through the finder. BTW, the TTL has some great optics. The acid test though will be the film results. More on sharpness in Part II. The main advantage this lens has over the 55mm, regular 75mm, 90mm and 105 is that it has f/32 DOF. Its DOF at 55mm at f/32 seems to be similar to the 45mm at f/22. This equates to having objects in the foreground that are larger than what the 45mm will show; a real advantage, especially in landscape work. Feel free to add comments about this lens. SR

-- Steve Rasmussen (srasmuss@flash.net), June 23, 2001

Answers

To add a bit to what Jim said,zooms beyond 2x can be sharp but it seems that they must be stopped down to rely on the diaphragm to lessen the aberrations. Shot wide open, these zooms have a distinct sweet spot in focal length that when it is deviated from, performance really drops off. Pentax has opted to retain wide open performance at all focal lengths by not having a huge range of magnification on this lens. There are just too many aberrations to correct when a lens is covering a large range of focal lengths. Curvature of field can't be corrected by stopping down so that has got to be a consideration when determining the focal length range of any zoom. This aberration has been a problem on fixed wide angle lenses so I'm sure it was with this zoom. Pentax made a good choice in keeping this zoom to 2x only.

-- Steve Rasmussen (srasmuss@flash.net), June 27, 2001.

I just finished some shooting with this lens at f/8 at the 55mm setting. All shots were done on a heavy tripod and exposed for over 30 seconds. Using a high quality loupe, it is obvious that at this focal length, this lens cannot be distinguished from the fixed lenses in the Pentax line. Prints of 24 x 30 inches can be made without problem. My results at the 100mm setting at f/8 were similar. Nice lens.

-- Steve Rasmussen (srasmuss@flash.net), July 05, 2001.

This zoom will maintain its focus as you zoom to different focal lengths, however, if you try this for macro work, the focus will change quite a bit as you zoom. Also, I have noticed that this lens has what's known as a "Sagittal Belly" when bringing an object into focus. This astigmatism goes away once the object is in focus however. I've noticed this on the 105 as well.

-- Steve Rasmussen (srasmuss@flash.net), July 14, 2001.

I agree with Steve's comments, and I also find this lens seems sharper wide open than the 105mm, and it's also sharper to me than the 45mm wide open. I find this lens to be sharp across all f-stops, although I tend to shoot mostly at f/32, and I've never done any real scientific tests. It's sharp enough for what I do, (mostly landscapes), and I'm reasonably picky. I use this lens about 75% of the time, and occasionally use the 45mm, 135mm, 200mm and 300mm lenses. I find the 45mm a little sharper and maybe a bit more contrasty than the 55-100 zoom, but not appreciably so. My only wish is that this lens was a 55-150 zoom, then it would be in the very useful 28-70 (35mm) equivalent range. It would probably also weigh twice as much, and it's weighty enough as it is, but I don't find the weight that much of a problem with the 67II body. With the older 67 body, it's a bit much to try to handhold this combination.

I also wish I could solve the vignetting problems I get when using my HiTech 4x5 filter holders and shooting at the 55mm setting. I also wish this lens had some depth of field markers, but then again, if they weren't any more accurate than the ones on the other Pentax lenses they wouldn't be very useful. I've gotten used to carrying around a depth-of-field card with me, and maybe someday, my overwhelmed brain will actually memorize the hyperfocal distances.

-- Bryan Flamig (bryanflamig@home.com), June 25, 2001.

Since this is my only lens for my 67II, I have nothing to compare it with in the Pentax line. Compared to my Nikkors in this focal length, I find it every bit as sharp. Distortion at the edges at 55 is minimal. I think the zoom range is just right for my needs. A 2X zoom is still the max that can be achieved without significant sacrifices in optical quality (IMO), but Steve can offer more substantial comentary in that arena.

Handling is excellent for a lens of this size. However, the 95mm filter diameter does make adding filters a significant consideration financially.

IMO, I think Pentax did an excellent job with their first zoom for this venerable system. I still plan to add the 45, 165 and 300. I think a zoom in the 150-300 range would be another winner.

-- Jim Korczak (korczaks@ptdprolog.net), June 26, 2001.