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08-30-2010, 11:21 AM - 1 Like   #1
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Lens Comparisons, some 50s to start with.

Hi, during the summer I (again) had the chance to borrow my friends K20D to do some testing. Some of you might remember that I did a similar comparison last year, but screwed up the focus on one of the lenses. So now I'm back with a more extensive and better executed test.

I will update with more pictures and results in time. But for now I'll post the first part of the comparison, centre sharpness at different apertures.


The lenses that take part in this test are:



From left to right, Pentax DA AL II 18-55/3.5-5.6, Pentax 50/1.2, Pentax 55/1.8, Pentax 50/1.4, Pentax M 50/1.7, Super-Takumar 55/1.8 and Takumar 55/2.2

I chose to include the DA 18-55 because it's such a common lens and many people can relate to it, also the M50/1.7 and K55/1.8 are common lenses so I think most people should be able to relate to the results.



100% crop from centre of image



My Conclusions:

My first thought when putting together the chart was that the M50/1.7 is amazingly sharp at f/2, with the two 55/1.8s not far behind. The M50/1.7 reaches it's peak quickly and stays there up until f/8 where it starts to fall of. Very impressive.

The two 55/1.8s show a similar development, peaking at f/4-5.6, and holding out until about f/8. The SMC version has a little edge over the Super-Takumar, this might be the result of the better contrast it has probably thanks to the SMC coating.

The oddball Takumar 55/2.2 that came with my 1958 Pentax S is quite soft wide open but definitely up there with the two 55/1.8s at f/4-5.6, after that it gets soft again. However, being comparable to the SMC K55/1.8 is not at all a bad score for any lens.

The DA compared to the rest at f/5.6 is of course terrible, but that is to be expected when comparing a stopped down prime to a wide open zoom fully zoomed in. But stop it down to 8 or 11 and the results are already much better. I'd say it's about as good as the Takumar 55, and better when getting to f/16-22. But it not as sharp as the other primes, for example it doesn't ever reach the level of the M50/1.7 at f/2.

Now the K50/1.2 and K50/1.4, the two I personally am most interested in. Is the 1.2 only a extreme lens for bragging and the 1.4 a much more sensible choice? Or is there any real sense in getting the 1.2? Wide open they are quite close in my opinion, I have a hard time deciding which I think is the sharper. They are both quite foggy but in pure sharpness terms it isn't all that bad, even at 1.2! But most critically, and this was what I originally wanted to find out when I started my tests last year, the 1.2 stopped down half a stop IS noticeably better than the wide open 1.4, and that in itself gives me enough of a reason to own the 1.2. It is in fact very near the 1.4 stopped down to f/2. From f/2.8 up to f/11 the 1.2 seems fairly consistent, equal or better than the M50/1.7. I don't know if this has reached the limits of what the K20Ds sensor can produce or if they are indeed that equal and similar. The 1.4 doesn't do a bad job either, it seems to reach it's top at about f/4 and stay there until I screwed up the exposure at f/11-16 (don't know how this happened...).

In this part of the test I would have to say that the k50/1.2 comes out on top. Because of the picture quality stopped down half a stop to match some of the others wide open. Also it is among the sharpest when stopped down to optimum aperture. But the M50/1.7 and the two 55/1.8s are really impressive stopped down to f/2, simply very good sharpness at that aperture.


More to come later. All questions, opinions and comments are welcome.



Last edited by Jimfear; 08-30-2010 at 11:54 AM.
08-30-2010, 12:10 PM   #2
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Thanks for a very interesting review. I own the M50 1.7 and like u said it is an amazing lens. There has been a lot of threads about comparing the 50's prime between f1.4, f1.7 and the f2, first time i see someone throw a rare f1.2 into comparison, nice job ! I like how you throw a DA zoom into the mix as well, i guess you want to show what is the big difference between what prime and zoom lens can do.
08-30-2010, 12:29 PM - 1 Like   #3
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I don't have time to look at the results right now, but I wondered if you are using a lens shade for these tests? It's been proven that the FA 50mm 1.4 for example loses contrast if not used with a hood because of its prominent front element.
08-30-2010, 12:41 PM   #4
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QuoteOriginally posted by taiweitai Quote
Thanks for a very interesting review. I own the M50 1.7 and like u said it is an amazing lens. There has been a lot of threads about comparing the 50's prime between f1.4, f1.7 and the f2, first time i see someone throw a rare f1.2 into comparison, nice job ! I like how you throw a DA zoom into the mix as well, i guess you want to show what is the big difference between what prime and zoom lens can do.
Thanks. Yes I wanted to make the results understandable to as many people as possible, and that's best done by having a lens many people have used among the lenses tested.

QuoteOriginally posted by audiobomber Quote
I don't have time to look at the results right now, but I wondered if you are using a lens shade for these tests? It's been proven that the FA 50mm 1.4 for example loses contrast if not used with a hood because of its prominent front element.
I didn't use a lens hood with any of the lenses, it was easiest that way. However the test was shot in the shadow so that should help the problem a bit.

08-31-2010, 05:36 PM - 1 Like   #5
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"In this part of the test I would have to say that the k50/1.2 comes out on top."

AGAIN. I can't help but smile when testing like this, inclusive of bokeh rendition put the SMCP-K 50mm f/1.2 at the top of the class. And people scoff at us who own them and say that such speed is unnecessary. It's nice to be vindicated.

Also, did you notice that the 50mm f/1.7 is slightly longer than the other lenses?...I actually think it is more of a 53~54mm lens. The actual focal length of the SMCP-K 50mm f/1,2 is 51.8mm

Last edited by Digitalis; 09-01-2010 at 12:34 AM.
08-31-2010, 05:55 PM   #6
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QuoteOriginally posted by Digitalis Quote
"In this part of the test I would have to say that the k50/1.2 comes out on top."

AGAIN. I can't help but smile when testing like this, inclusive of bokeh rendition put the SMCP-K 50mm f/1.2 at the top of the class. And people scoff at us who own them and say that such speed is unnecessary. It's nice to be vindicated.
+1 to you
09-02-2010, 02:00 AM   #7
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Now for part two of the test!

I did this test to get a "second opinion" on my results. This is basically the same as the last test but in a more controlled environment, alas I still managed to make some errors here. But they are easily found. The Super-Takumar and Pentax 50/1.2 are front focused, the 1.2 more so. You can still somewhat compare them as the focus is still visible, just not in the right place.


WARNING ALL MODEM USERS! LARGE FILE!

Anyway here are the crops, centre of image



More conclusions:

Here we see about the same thing as in the last test. The K50/1.4 get a chance to show how good it still is going up to f/16-22 where many of the others go quite soft. Nothing more to report really, just confirmation on what the last test showed us.




Still to come, bokeh test! Stay tuned.
09-02-2010, 02:54 AM   #8
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QuoteOriginally posted by yeatzee Quote
+1 to you
make it +2

09-04-2010, 11:19 AM   #9
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Time for the third and last part of my 50mm comparison!

This is in my opinion a very interesting part of the test. Sharpness is one thing, but when dealing with 50mm lenses few are bad in that respect. Bokeh on the other hand can vary greatly and that is what we are going to look at now. I did test shots from wide open to f/4, and naturally the DA Zoom couldn't enter as it start from 5.6 when fully zoomed in.

Included in the files are full scene pictures and 100% crops of strategic spots. The full scenes are about 45% of the original.



WARNING! LARGE FILES!

Takumar 55/2.2

Super-Takumar 55/1.8

SMC Pentax 55/1.8

SMC Pentax M 50/1.7

SMC Pentax 50/1.4


SMC Pentax 50/1.2



My Conclusions:

Keep in mind that these are my opinions and I don't make any claims on which is the "best" bokeh, everyone has their own taste when it comes to this...

The Takumar 55 has a quite busy bokeh that can be distracting, for example looking at the upper right part of the picture. It does settle down at f/4 though. Highlights can be quite harsh also. One interesting thing with the Takumar is that it seems to produce an almost round highlight bokeh even stopped down! Kind of like those 18 apertureblade monsters.

The Super-Takumar 55 has a smooth bokeh, it does quite well in melting the highlights also. In my opinion it has a very pleasant bokeh at f/4 and a good bokeh from wide open up to that.

The SMC Pentax 55 performs like the Super-Takumar 55, and that is to be expected with the same optical construction. I have a hard time telling these two apart, the only thing I think could differ is that the SMC version is a little bit harsher in it's bokeh, but that could just as well be changing light conditions.

The SMC Pentax M 50 also has a pleasant bokeh in my opinion. It controls the highlights well and is overall quite smooth. Though it is not as good wide open as stopped down.

The SMC Pentax 50/1.4 is a bit harsh wide open again looking at the upper right part of the picture. But stopped down it is smooth and pleasant, and the highlights are also quite well controlled.

The SMC Pentax 50/1.2 then... well... I guess this is what we call melting a scene. At 1.2 it is very smooth and basically a world of smudge. Highlights do stand out as round dots but it is still very good compared to the others, for example looking at the orange highlight in the bike wheel that almost doesn't show round dots where the others did have highlight dots. At 2.8 it is a little bit harsher but still not bad. Highlights tend to get more visible as you stop down.



This was the end of my 50mm comparison, but I will continue with less extensive tests of other focal lengths.
09-05-2010, 01:54 AM   #10
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Great work, Jimfear. You must be exhausted after that little lot!

For what it's worth, this would be my personal conclusion from your endeavours:

Best bokeh, and best overall, is the f1.2.

Next best bokeh (somewhat surprisingly), and best value for money, is the f1.7. (Actually this ties in with another recent thread which pitched it against the 55/1.8, but I think I was in a minority there.)

Next (again somewhat surprisingly) comes the f1.4

Last would be the 55/1.8 (either flavour).

I shall look at my M 50/1.7 with new eyes!

Thanks for a very interesting thread!
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