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09-10-2012, 04:19 AM   #1
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K 55mm F1.8 soft?

Hi all,

The first prime I bought for my K200D was an SMC PENTAX K55mm F1.8 (bayonet) off eBay.

I had read great things about it and enjoyed shooting with it for a while, before becoming distracted by other lenses such as the M35mm F2 and the K200mm F4. Recently, I went back to using the 55mm and found I enjoy that focal length on APS-C, because it makes the image the right size in the viewfinder such that I can open the other eye and shoot at the same time as seeing stereoscopically. Additionally, taking photographs at 55mm seems to aid my composition - I like the way I choose to shoot with this lens and the look it gives my pictures.

That is until I decide to zoom in or crop. I've noticed when looking (too) closely at my pictures (including extensive home test shots) that this lens seems to lack contrast and sharpness around the finer details of the picture. There is a soft halo-ish fringe kind of effect over contrasted edges.

I acknowledge that these lenses are a challenge to manally focus, and I expect to miss the focus sometimes - but even under test conditions on a tripod, I seem to get the same effect. It happens at almost the whole range of F stops, but is more obvious when the lens is towards the wide end.

The same fuzziness does not present when shooting with the Takumar, A series or M series 50mm lenses that I have tried.

My question for current or previous owners of the K55 F1.8
is this how the lens is supposed to be? ( or have I got a lemon? )

Cheers,

09-10-2012, 05:17 AM   #2
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Could you post examples or give a link?

Also, did you double check for haze inside the lens?
09-10-2012, 05:47 AM   #3
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A k lens may not have some of the coatings that we are used to that provide additional contrast when there is lots of stray light.

In addition, are you using a properly sized hood? My Sigma 50 F1.4's hood is sized for FF's, and can lose contrast and get bloomy on my k-x when shooting wide open. Stopped down one stop, and it's all good.
09-10-2012, 06:03 AM   #4
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Is there a filter screwed on there? A used lens i bought came with a filter which I didn't even notice at first glance

09-10-2012, 07:06 AM   #5
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Hi Wasting
I have the SMC PENTAX 1:2 55mm. According to Tak service manual here the same lens was named 1:2 and 1:1.8
This lens is not a challenge, it is a delight to manually focus because the image is so bright in the VF and it feels like a $million compared to a modern plastic lens.

Here is a portrait in harsh Michigan morning sun, I tried to focus on the Qantas strap for you to compare.
At f/4 the stop watch face is over exposed but I was at 1/3000th and iso 200
https://www.box.com/s/1uqzbncivksdgpey83gc
At f/11 and 1/180th more normal for that light:
https://www.box.com/s/upn78x38izldloo58k0u
09-10-2012, 09:03 AM   #6
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The K55/1.8 has color fringes in high-contrast out-of-focus areas that are typical of the K series. You can see it in Wombat's first image to the right of Spiderman, the bright reflections off the lawn light. Your K200/4 probably does the same thing. I know I used to see it in my K135/2.5 and my K300/4. That doesn't sound like your problem, though. You should be able to demonstrate this effect with a newspaper shot at an angle, lens wide open, at a distance so some of the text in the center of the page is in focus. Text close to you should have a green fringe, then no fringe in focus, farther away purple.

I haven't tested mine. My feeling is that it's not quite as sharp as the Pentax 50mm f1.7 formula, but I have never seen it be not sharp enough. As long as the focus is where I wanted it, I love the look. It ought to be sharper than the kit lens or just about any zoom.

Wide open, minimum distance:

09-11-2012, 12:17 PM   #7
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The SMC K 1.8/55 is really sharp! This is a 100% crop of a photo taken with K7 at f/5.6 (itīs the Super-Takumar 1.4/50 (v1) in the photo, by the way).

Last edited by jt_cph_dk; 09-11-2012 at 12:25 PM. Reason: text edit
09-11-2012, 01:47 PM   #8
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The Pentax-K 55/1.8 should be anything but soft and/or low contrast. Mine is easily my best fast 50. Not favorite, but definitely my best.



Steve

09-11-2012, 03:54 PM   #9
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K55 is anything but soft or lacking in contrast. If anything its capable of lovely dreamy colour transitions and deep rich colours. I would call it a warm lens
Couple of examples @ f/1.8





09-11-2012, 07:41 PM   #10
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tested my K 55mm 1.8... wide open under halogen light from 1.5 feet and no post processing.


Last edited by MysteryOnion; 09-12-2012 at 09:55 AM.
09-11-2012, 11:36 PM   #11
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QuoteOriginally posted by Wasting Light Quote
There is a soft halo-ish fringe kind of effect over contrasted edges
QuoteOriginally posted by Just1MoreDave Quote
The K55/1.8 has color fringes in high-contrast out-of-focus areas that are typical of the K series
I think this is it. And the solution should be, to stop the lens down a bit, when taking such photos with high contrast edges in color (alternately shoot B&W). Or give a damn, because it is only seen with very close inspection/large printing and can also be corrected in the post process. The problem is more pronounced with the K2.5/135 as these two photos show, or perhaps it is just the higher contrast/darker background in the second photo and maybe I stopped down a little more with the K55? they where shot at around f/4 - 5.6 (look on the bright, left edge of the yellow rose):

1.8/55


2.5/135


Regards

Last edited by jt_cph_dk; 09-11-2012 at 11:50 PM. Reason: added text
09-12-2012, 09:07 AM   #12
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QuoteOriginally posted by Wasting Light Quote
There is a soft halo-ish fringe kind of effect over contrasted edges.
This is to be expected when shooting wide open. However, the halo should disappear when stopped down--assuming of course that you're not shooting in flare-ey conditions without a lens hood through a dirty filter.

Have you checked for haze or fungus on the lens elements? A flashlight is helpful for this.

I treasure my copy of this lens.
09-15-2012, 03:31 AM   #13
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Original Poster
Thank-you to everyone who replied to my initial post.

MysteryOnion and Johnyates;
I'm going to attach some examples to this post. The lens is free of definitely free of fungus.
It doesn't look hazy either, but I'm not an expert when it comes to haze.
What are some indications that the lens may be hazy?

JinDesu;
You may have a point about the coatings.
I'm not using a hood of any kind on this lens.
Most of my pictures with this lens are taken indoors.
Do you think it is worth trying a hood to block stray light indoors?

Just1MoreDave;
When I nail the focus, the lens is definitely sharper than the kit lens, but not a great deal sharper.
I hadn't noticed 'colour' fringing with the K 55mm, it's more like 'white' fringing if such a thing existed.

jt_cph_dk;
The crop you posted of a lens looks fairly sharp. I get the feeling it is sharper than I could accomplish with my lens.
Are the photos of the yellow rose cropped or a resize? Lens discussion aside, I really like the picture of the rose you took with the 55.
The subtle fringe you describe on the edge of you roses is hardly noticeable and not what is happening with my lens.

stevebrot and robbiec;
Great photos. Love the bokeh.
Although, on resized photos of that size, I don't think the soft halo/fringe would show itself if it had been there at the original size.

Attached to my post are images comparing my K55mm F1.8 with an M50mm F2 and an A50mm F1.7, each of the three at F2, F4 and F5.6.
Conditions were inside, under warm flourescent lighting, from about 3m distance, ISO 200, tripod mounted, remote shutter, using the camera to meter each exposure. I focused using the camera confirmation, and by focusing past the subject, then bringing the focus back towards me until I got the confirmation. I do this because I feel it gives me better results then if I focus towards the subject. The subject is a blue fridge magnet with white text.
Attached Images
     
09-15-2012, 06:04 AM   #14
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QuoteOriginally posted by Wasting Light Quote
jt_cph_dk; The crop you posted of a lens looks fairly sharp. I get the feeling it is sharper than I could accomplish with my lens. Are the photos of the yellow rose cropped or a resize? Lens discussion aside, I really like the picture of the rose you took with the 55. The subtle fringe you describe on the edge of you roses is hardly noticeable and not what is happening with my lens.
Iīm sure that your lens is faulty somehow. Maybe it has been dropped and glass knocked out of place (any exterior marks?)? Or perhaps hazy, as you suggest? Itīs not anything as sharp as my sample. They are quite abundant and cheap to get (I just got another close sibling, the K2/55 for free from a friend and saw another K1.8/55 locally for 20US sitting on a 70ties KX!), which is strange because they substitute the popular 85mm on APS-Cs and are truly great portrait lenses (?). Probably not worth the price of a repair and a better idea to get another one or try cleaning/resampling it yourself..

Thank you very much for your comment on my yellow rose photo, by the way. Regards
09-15-2012, 07:35 AM   #15
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Yeah I would try another copy, mine is very sharp and does not have that issue.

Phil.
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