[Marc Sabatella]

I went ahead and uploaded the side-by-side comparison images to a place on my own web site where I could link to them directly. So if you go back and look at my post three responses ago, you'll now actually see all the images.

Really, the main conclusion I think one should draw is that all three are good lenses, each with their own particular strengths. For raw resolution when comparing objects at the same magnification, they fall in focal length order: 100 best, followed by 120, followed by 135. When comparing ability to resolve detail at infinity, that order is exactly reversed, because the longer the focal length, the greater the magnification, and the difference in magnification is greater than the difference in resolution. In order words, nothing is anything but what one would normally expect.

[eddie1960]

Some very good comparisons here Marc. I will give a big plus one to the PF comment on the m100 f2.8, I hadn't noticed it either as i hadn't used it in a problems situation, then when i was out and had only it and a 28 in my bag i heard a woodpecker going at a tree, I stopped and moved in as tight as possible with the 100, there were a lot of branches against a bright blue sky, the fringing was crazy, the shot next to unusable in colour. live and learn, I wish I'd had the k135 3.5 with me
on the flip side in clubs it's a great lens, and also pretty good for portraits

[Marc Sabatella]

It had been bugging me that I couldn't get the purple fringing comparison to work right - for whatever reason, every time I took a screen shot of the window comparing the images, the sky turned purple. And if I tried generating crops, the fringing was reduced across the board (ACDSee's demosaicing algorithm apparently results in less fringing than the camera's). While I could have tried regenerating the crops in the Pentax software, I've opted for a different solution. I've taken the comparison screen shot - purple sky and all - and processed it to take the exposure up one stop. That washes out the sky enough to not be as much of a distraction, and it really brings out the fringing, too. So I've again updated my previous post to include that image.

I thought it important because aside from bokeh (which I find subjective), this was really the only aspect of the comparison that couldn't have been predicted and indeed seen as all but inevitable just from thinking about the difference in focal lengths.

Bottom line, I'd characterize the three lenses as follows:

- The 100 is the sharpest when comparing images at constant magnification (by a small margin over the 120 and a larger margin over the 135). And not that the others are particularly large or heavy (they aren't!), but the 100 is *noticeably* smaller and lighter. However, it has the most purple fringing by far, it lacks a built in the hood, and it can't blur a background to the same extent as the other two. It is the most generally useful portrait focal length of the three, but it has the least "reach". It is not too hard to find with a little patience, and it usually goes for $100-$150.

- The 135 is the slowest of the three by a half stop (or a little more), but it can resolve the most detail in distant objects (by a small margin over the 120 and a larger margin over the 100). Thus, it's the pretty clear choice for most outdoor shooting, where you want the reach and where being half a stop slower isn't as much of an issue. Indoors, its length and slower speed make it not as good a choice as the others most of the time. Although in large and reasonably well lit spaces, I have found that it can and does shine. This lens is easily found any day of the week for under $100.

- The 120 is exactly the compromise between the other two I hoped it would be. More "reach" than the 100 (and with a built in hood); faster, wider, and sharper than the 135 when used indoors at closer range. The fact that it also has the least purple fringing and, for me, perhaps the nicest bokeh, is a bonus, although it does prove to be marginally slower than the 100 (less than a quarter stop). If you're looking for a good general purpose medium telephoto lens for both indoor and outdoor use and fear a 100 would be too short too often and a 135 would be too long too often, the 120 is your lens. Unfortunately, it is much harder to come by than the others. It usually sells for $150-$200, but you may have to wait a while for the chance to buy one.

[Jonathan Mac]

Great analysis Mark. To be added to the reviews section of all three..?

I´ve had my eye on an M120 for a while, but it´s going for too much for me to justify it given that I have the other two (& I don´t use them very much).

The 100´s weakness (very much like the M 85 f/2) is the colour fringing, which is unfortunate.

[Marc Sabatella]

Thanks! I do plan to update my reviews of the 100 and 135, and add one for the 120 - but I still want more real world experience with the latter.

As for the 100's color fringing, it managed to never bother me for years while I shot in clubs, so it's not going to start bothering me now, but it's a legitimate concern for outdoor use. It does of course subside as you stop down, though, which you would normally do in conditions bright enough to trigger this problem to any great extent.

Realistically, for someone who has the 100 and 135 but doesn't use either much, the 120 is not likely to be worth it. It's great for someone like me who actually uses both the 100 and 135 a lot but would prefer not to have to take both and is still holding out against getting bigger/heavier/pricier zoom, or for someone who has nothing in this focal length range and wants to fill that need with one prime but has been having trouble deciding between the 100 and 135.

[repaap]

I got my M135 just to get familiar with this world of teles. I think that I'd love tho have 120, but I have yet so much to explore with this. It is surelly little soft somewhat, but color and contrast is good. Good test with these lenses.

[Just1MoreDave]

Congratulations on the new lens and a nice test. I think I can still pretend that the M120/2.8 is a senseless luxury for me.

I should check my S-M-C Takumar 105/2.8 for fringing. I don't use this lens very much at all.

[erangel]

I was very lucky to find here in Panama a copy of the M120/2.8 in excellent condition!
Marc, I used your review on the lens database and this comparison to make a decision. Thank you!

[paperbag846]

Thanks for the comparison, Marc. I think the 120 looks worth tracking down for outdoor stuff. Do you find it flares up more than usual?

[macTak]

Thanks for the comparison, Marc. I think the 120 looks worth tracking down for outdoor stuff. Do you find it flares up more than usual?

While I'm not Mark, I also use this lens a fair bit. While I haven't really taken any stots with it pointing directly into the sun, from my general usage I've never encountered any flare problems. In fact, in my experiance I'd say it's better at handling flare than the S-M-C Takumar 135mm f2.5 (version 1) and the Tamron Adaptall 2 135mm f2.5.

[Marc Sabatella]

On a lark, I *have* tried doing some DA15-style starburst shots. I don't recommend it :-). Aside from that, no, it doesn't suffer any ore flare than any other lens, and the built in hood makes it noticeable better in that respect than the 100, unless of course you use a separate hood for that. Not sure if the 120 really makes more sense than the 135 for primarily outdoor usage, though, except perhaps for the CA/fringing issues with the latter.

[icedoghans]

Is it my imagination or do the 135mm photos have more red in them? Regardless, I appreciate your comparison, as I am a total neophyte to this.

....rog

[Marc Sabatella]

I made no effort to equalize white balance, so i wouldn't attribute any difference in color to the lens itself, except for the purple fringing.

[pacerr]

You deserve a meritorious day off for this report, Marc.

Some time ago I did something similar, but less ambitious and quite informal, with a half dozen lenses -- Super Tak's, M's, Adaptall's, Vivitars, the DA 50-200 -- in the 90 - 200mm range.

Some things I've noted that generally agree with your findings:

- So long as image quality is acceptable and reasonably close to equal among lenses, the longer FL will normally produce the best overall results. (I'd add that I typically crop for finished composition and format in most instances so FF absolutes aren't a controlling factor.)

- Most of my mid-tele lenses seem to be "designed" or best suited more for either long(er) distance telephoto or for close-up/portraiture use. Or at least perform more to my liking in various conditions. I seem to notice the difference beginning in the 12-18 ft range and tend to choose a lens for that application.

More often, I choose to use a lens for reasons that have no rational explanation other than that it's either a pleasure to use or has predictable technical qualities for a specific application. Without the burden of post-shot comparison exercises I'm blissfully unconcerned with the potential differences -- but then I have no one to please but myself and have no one to blame for my impulsive choice of glass.

H2

[womble]

Interesting review. The M100 is one of my most used lenses. I have the clip-on plastic hood but got fed up with it being knocked off so I got a metal hood designed for the Takumar 105 that fits nicely and works very well. For 135mm I have the K135/2.5 which although a wonderful lens (it compares very favourably with my DA* 50-135mm) is much heavier and larger than the M100.

Thanks again, Kris.