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03-18-2011, 02:16 PM - 2 Likes   #1
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Shootout: M100/2.8, M120/2.8, M135/3.5

Now that I have the M120/2.8 to join my M100/2.8 and M135/3.5, I figured I'd do a little comparison. Nothing terribly scientific, but I did spend some time trying to get results I at least would find useful. The first couple of images below shows the three lenses themselves - 135, 120, 100. As you can see, the 120 is between the other two in size when viewed from the side, but shows the most glass when viewed from the front. It actually weighs exactly the same as the 135.

Next are a pair of composite images comparing all three lenses plus the DA50-200 set half way between 100 and 135. I made two sets of tests, one in which I stayed at the same distance to subject, and one in which I adjusted distance to subject to keep the subject more or less the same size in the frame. I figured this would correspond to how one might use a lens for portraits, so those are the comparisons I am posting here.

The first composite shows all four lenses shot at their maximum aperture. Top row, L-R: M100 @ f/2.8, M120 @ f/2.8. Bottom row, L-R: M135 @ f/3.5, DA50-200 @ f/4.5. DOF was shallow enough at this distance that it was difficult to get them all focuses precisely the same, but the place where I have made the comparison is pretty representative. It shows only a fairly small difference, which matches what I saw in the rest of the images. I'd say overall, the M100 wins, followed closely by the M120, with the M135 and DA50-200 noticeably behind, but still quite good, really.

The last image shows the same four lenses at f/8. I'd say the same basic order holds here, with the gap between the M100 and M120 on one hand and the M135 and DA50-200 widening slightly.

The comparison I made at constant distance were designed to show me if the M120 was close enough to the M100 in resolving power to actually pull out more detail from a given distance. This turned out to be a bit inconclusive, but my impression is, the 120 probably wins slightly at f/8, but it's a wash wide open.

I've uploaded the individual pictures themselves to a gallery in picasaweb for anyone interested in such things:

https://picasaweb.google.com/MarcSabatella/MediumTelephotoShootout#

Focal length info is in the EXIF. Aperture is not, of course, but it should be easy enough to figure out from shutter speed. Anything in the 1/2000" range was shot wide open, anything around 1/250" was shot at f/8.

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03-18-2011, 03:31 PM   #2
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You may want to blow out that dust from the edge of the front elements of your 135 and 100. I'm sure it doesn't affect results, but it may lead to fungus long term.
03-18-2011, 04:21 PM   #3
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Looking at the quick test images, apart from the maximum aperture, I think the lens of choice for most people would be the DA 50-200mm because it is cheap, so widely available, has AF, allows use of every exposure mode and exposure metering, has versatility on focal range and performance is pretty good when compared to the M telephoto primes.
03-18-2011, 04:23 PM   #4
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Good to see you back at posting Marc... We've wondered what happened to you (there is even a thread in GT IIRC).. Looking forward to seeing your concert photography with this lens. It's one I've had my eye on too but don't get very many samples.



03-18-2011, 04:38 PM   #5
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Wow the DA50-200 faired better than I was expecting, although significantly slower of course.

I have a M42 135 f3.5, that I love - although some of this is just the feel of the wonderful manual focus! Otherwise its just somewhat faster than my DA-L 55-300.
03-18-2011, 07:09 PM   #6
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Thanks for the kind words. BTW, nothing "happened" to take me away for the forums; I just got got very busy, and once I got out of the habit of checking in every day, that slice of time just disappeared. I don't know that this has really changed again. But you know how, after getting a new lens, you just have to talk to someone about it - and who else but the folks here at Pentax Forums?

Oh, and I absolutely agree that one of the lessons of my test is that the DA50-200 (my copy, at least) is nothing to sneeze at, despite what "they" say. I actually use it without reservation for daytime / outdoor concerts. But in the clubs, that extra stop and a half makes all the difference in the world.
03-18-2011, 09:53 PM   #7
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Thanks for a very interesting test. You make me wish I had time to do and put up a test of my M120 and M150, along with my S-M-C Takumar 135mm f2.5, Tamron AD2 135mm f2.5, and DA-L 55-300mm. But my favorite from just usage is definitely the M120. Really the size (espically with the built in hood, which the M100 does not have) and weight of it is fantastic for its reach and speed (smaller than even the M135). Plus I find it to have excellent sharpness, even wide open. 8 aperture blades is a nice feature too.

I will add a comment on bokeh, since you didn't test for that. The M120 does not perform like a portrait lens in terms of its bokeh. Really it is vastly different than the two fast 135mm primes I listed above. Both of those are somewhat under-corrected for spherical aberration in the OOF behind the plane of focus (i.e. wide open they show a more Gaussian blur in the PSF, but also with a somewhat brighter ring around the edge), leaving the bokeh rather creamy generally. The M120 is rather neutral, a little overcorrected (most similar to my M50/1.7 I suppose, although that is kind of a weird comparison). Still, I generally quite like the bokeh it produces, and it often does come other smoother than I even expected. It's excellent for street-style photography, etc (I use it for any general mid-tele shooting). But it is clearly not designed primarily as a portrait lens, and the optical design reflects that--it has the same basic optical design as the M135, not the M100 (which is a different design, like the K105 and Takumar 105mm lenses but with a rear group of two lenses instead of a doublet. I seem to recall that this was designed more as a portrait lens, so perhaps the bokeh is better--then again, I must say I'll take the M120 any day over my Super Tak 105mm in all regards).

There is one final benefit about the M120 no one seems to mention--it is the longest focal length on APS-C where you can hand-hold a shot with flash at the X-sync speed without particular worry of shake.

Last edited by macTak; 03-18-2011 at 09:58 PM.
03-18-2011, 10:56 PM   #8
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QuoteOriginally posted by macTak Quote
...
I will add a comment on bokeh, since you didn't test for that. The M120 does not perform like a portrait lens in terms of its bokeh. Really it is vastly different than the two fast 135mm primes I listed above. Both of those are somewhat under-corrected for spherical aberration in the OOF behind the plane of focus (i.e. wide open they show a more Gaussian blur in the PSF, but also with a somewhat brighter ring around the edge), leaving the bokeh rather creamy generally. The M120 is rather neutral, a little overcorrected (most similar to my M50/1.7 I suppose, although that is kind of a weird comparison). Still, I generally quite like the bokeh it produces, and it often does come other smoother than I even expected. It's excellent for street-style photography, etc (I use it for any general mid-tele shooting). But it is clearly not designed primarily as a portrait lens, and the optical design reflects that--it has the same basic optical design as the M135, not the M100 (which is a different design, like the K105 and Takumar 105mm lenses but with a rear group of two lenses instead of a doublet. I seem to recall that this was designed more as a portrait lens, so perhaps the bokeh is better--then again, I must say I'll take the M120 any day over my Super Tak 105mm in all regards).

There is one final benefit about the M120 no one seems to mention--it is the longest focal length on APS-C where you can hand-hold a shot with flash at the X-sync speed without particular worry of shake.

Hm, this makes me want to see a bokeh comparison between the three... Marc?


(when you get the time sir)

.

03-19-2011, 01:07 AM   #9
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Nice test. Bokeh compare would be nice IMO too, If you have time
I just bought M 135/3.5 just to try out this M quality on longer(that 50) tele. DA 50-200 seems to be good lens. Some how I have feeling that it is not so good, by forum, but you should not trust blindly at these test eh
03-19-2011, 07:59 AM   #10
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OK, I'll try to get a bokeh comparison happening. Any suggestions on how best to do that? I found macTak's comments fascinating - things I would not have known at all (and don't yet completely understand, but that's OK :-). The fact that the 120 has 8 blades rather than 6 was pointed out to me in the thread where I first posted about getting the 120, and the most common observation made about the first image I posted there (which was shot at f/4, so the blades did come into play a bit) was about how nice the OOF areas looked. The fact that the M120 is basically the same design as the 135 probably explains why its performance is so similar.

I also plan to do a test at closer to infinity, since telephotos are often used for, well, "tele".

I notice, BTW, that the composition comparison images were reduced in size with no click-thru option to see the full size version. So I've posted those to the picasaweb gallery. If anyone knows of a way to embed a full size image from picasaweb here, I'd be happy to do so, but I can't get anything but more reduced size version. So instead, here is a link to the page with the wide open comparison:

https://picasaweb.google.com/MarcSabatella/MediumTelephotoShootout#5585795382000537746

Click the magnifying glass to the upper right of the image to get to a screen where you can then adjust a slider to make it bigger.

I also added captions to the images to make figuring them out easier.

As I keep going over the images, looking around at other parts of them and trying to account for differences in focus point and DOF, I'm more and more coming to the conclusion that the M100 is the star here, with the rest more or less the same, although even so, difference between the 100 and the rest isn't huge.
03-19-2011, 08:22 AM   #11
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Nice job. Looks interesting.
03-24-2011, 12:09 PM   #12
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BTW, this coming weekend looks like a good time for me to actually do some more testing. I'd still appreciate advice on what people would like to see regarding bokeh.

Meanwhile, I doing little informal comparisons when I have a spare minute, and I'm coming to realize (or at least) suspect a few more things:

- On the occasions when I achieve the same precision of focus in the same spot with all three lenses, the lenses are practically indistinguishable when it comes to sharpness. But since my tests are usually done at close to minimum focus distance, DOF is shallow enough that this proves very difficult.

- The M120/2.8 is the hardest of these lenses to focus for me. The M100/2.8 has noticeably more DOF wide open. I gather the DOF of the 120 is, in theory, virtually the same as the M135/3.5 for a given subject distance, but the viewfinder image is that much larger for the 135, which helps in getting precise focus. And the 120 seems to show the biggest discrepancy between what *appears* to be in focus in the viewfinder versus what is *actually* in focus when shooting wide open. And I don't mean that in the sense of having a fault camera/lens - I mean, the focus screen is *known* to show too much DOF when shooting large apertures, and this is most acutely true for the 120.

- I've always know producing good tests to be hard, but this is driving the point home really well.

- My initial crack at doing an infinity test - seeing which lens can produce the most detail out of a distant object - goes as you'd hopefully expect. That is, the difference in focal length is more important than any difference in sharpness. The longer the lens, the more detail you get in distant objects, so you can banish any thoughts that cropping an image from the 100 might beat one of the others. However, the 135 really does come quite close the DA50-200 at 200 in terms of being able to show detail in distance objects - a crop from it really does look almost as good. In that sense, the 135 actually seems "closer" to the DA50-200 at 200 than it does to the 120. I'm not sure if that's due to focus issues on my part with the 120 (less likely at infinity), or if the 135 is more "optimized" for distance than the 100 or 120. But as things appear to me right now, I'd say the 135 is easily the best choice of these for someone looking for a general purpose telephoto to be used mostly for relatively distant objects. It renders the most detail in a distant object, it's the cheapest, and the most readily available. But for my purpose - low light photography in relatively confined spaces - it's pretty clearly beat in performance by both the other two. That's because the difference in speed is really important, and while I'm still not 100% sure about this, it does like both the 100 and 120 beat the 135 when comparing at constant magnification (the 100 more obviously so than the 120).
03-27-2011, 04:19 PM   #13
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I've finally managed to get some decent test images at a few different distances and different types of subjects. They were shot in good light and I used a variety of techniques to control focus.

I can't say the big picture changes tremendously, but some of the details do, to the point where I'm actually thinking the 120 might be the overall winner here. It's hard to be unbiased because it's the new baby, but if nothing else, I don't think I have to worry that I am sacrificing anything by using it.

In all tests where images are compared side-by-side, the order is 100, 120, 135 from left to right. The same order is used in the tests where the images are presented consecutively. For the side-by-side comparisons, once you click through to see the full size image, you will be looking at 100% crops in all cases except the bokeh test.

First up: shooting each at close to minimum focus distance, wide open. This isn't quite the actual minimum, as I wanted to give myself a few inches of play in my focusing. It's pretty hard to tell the 100 and 120 apart here, but the 100 gets slight edge overall. The 135 looks like it isn't getting as much magnification as it should (ie, focus distance too long), but that's in part because my shooting angle is getting shallower, which changes the perspective.



Now, here is a medium-short distance test in which I "zoomed with my feet" to get more or less the same framing of a tree, focusing carefully on one particular spot on the bark and chimping. Here again, it's pretty hard to tell the 100 and 120 apart, but this time, I think the 120 probably wins. In similar tests, the 100 might win by an equally small margin; seems to depend on distance and the nature of the subject itself. The 135 isn't *that* far behind, but it's not quite up to the level of the other two. Again, all lenses shot wide open.



In this one, I'm shooting a different part of the same tree (wide open again), but this time from a fixed position. Meaning, of course, they produce different magnifications. I find it hard to make comparisons as a result, so I took the liberty of resizing the images to the same basic proportions. Here, it is the 135 and 120 that are hard to tell apart. Focus is ever so slightly different, so while it looked at first like the 120 managed to beat the 135, I think that's not really true. On the other hand, the 135 doesn't really hit it's stride until we start to approach infinity focus, it seems to me. At this distance, it's maybe too close to call, but both clearly beat the 100, as they should, being 20% and 35% longer.



One thing I started noticing as I played with the lenses over the past week is that they respond different in terms of fringing. And the 100 is nowhere near as good as I thought in that department - it's actually considerably worse than the 135. I guess I shoot it so much in dark clubs that I had never noticed how easily it fringes under the right (wrong) conditions. I tried both with and without hoods, and a hood helps some, but my tests here were directly away from the sun so I didn't think the hood would matter, and since the others have built-in hoods and the 100 doesn't, I thought it pretty likely people would be shooting the 100 hoodless. So here is a comparison showing the fringing when shooting wide open in high contrast situations. I had difficulty producing this comparison shot, as the screen capture function turned the sky completely purple in this shot for some reason. I don't understand why but am perfectly willing to believe it has something to do with the purple fringing itself. Rather than fix the purple sky, I am just bumping exposure up in the comparison to make the fringing more pronounced. You'll see that none of the lenses are immune, but the 100 is easily the worst of the three by far (look at the branches especially), and the 120 is somewhat better than the 135. In the original versions (before the sky turned purple and I bumped the exposure), the 100 was the only one in which the fringing was immediately noticeable; the 135 was easy enough to spot if you looked for it, but the 120 only showed it on a few of the pine needles:



I did long distance tests both wide open and at f/8. Results are similar: the 135 clearly holds the most detail, followed by the 120, followed by the 100. This may or may not be obvious at first glance, but becomes so when you downsize the 135 and 120 images, as I have done. Here is the wide open version, which also shows more purple fringing (and some color artifacting in the sky in the 100 shot, which is again mostly a factor of the way the screen shot was grabbed):



And here is the f/8 version, in which the fringing has largely faded:



Finally, you all asked about bokeh. I still have no idea what it means to test for that. But here are images wide open and stopped down one click (f/4, f/4, and f/4.5), showing, of all things, my compost heap. I picked it because I kind of like how it looked in the background of one of my cat pictures - it a pile of interesting shapes and colors (and my cat apparently agrees, because he spend a ton of time there). I chose not to use 100% crops this time, but rather an only slightly zoomed in view for the comparison.

Here is the wide open comparison:



And the version stopped down one click:



Call this one however you like, but I'm partial to the 120, to the extent I see a difference I might care about.

That's enough of that. Now I'm looking forward to getting back to *real* shooting!

Last edited by Marc Sabatella; 03-30-2011 at 09:59 AM.
03-28-2011, 12:34 AM   #14
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Itīs nice to see all the comparisons youīd done Marc. In that last one, the 100 looks best to me, although itīs clear that it has better contrast than the other two, and is possibly sharper, and this may be disguising some of the fringing.

Fom your original test, the most interesting thing for me was that the 135 renders the colour of the denim differently from the others - itīs more purple. The DA lens has it as a lighter blue. The 100 & 120 seem to be the same. The Da difference I can understand but I would expect the three Ms to have the same coatings & therefore the same colour response.
03-28-2011, 09:56 AM   #15
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BTW, I wouldn't read too much into color differences - I left the camera on AWB and made no effort correct for that. I suppose I should have done one test specifically for that.
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