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09-02-2010, 01:50 PM   #31
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See I'm torn. The top images are the K55.

I like the colour of the 1.7 better. I'm not sure what that is al about but it is certainly more colourful. However, the muter tones of the K55 has a sort of nice look to it. It seems to work well with skin tones.

The k55's OOF areas are blurier. I sometimes would prefer this look. This lens "obliterates" the OOF areas better than the 50mm. However, neither really blurs as much as I would like at f4. I think I would need a nicer lens (1.4, with more aperture blades) for that sort of performance.

The question is... why would the K55 has smoother bokeh? Both lenses have 6 aperture blades... is it all focal legnth? Does it have to do with the physical size of the lens (the k55 is larger).

09-02-2010, 02:01 PM   #32
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I think the 1.7 just has more contrast. I just bought a k55 last night. I am pretty excited. I waited far to long.
09-02-2010, 02:25 PM   #33
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Congrats!

I'd love to think what you think of the K55, and ho it compares to your other 50's.

I'd love to hear whether I should sell mine... or risk starting a hopelessly large collection of 50's!!!
09-02-2010, 05:37 PM   #34
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QuoteOriginally posted by paperbag846 Quote
I'd love to hear whether I should sell mine... or risk starting a hopelessly large collection of 50's!!!
Sell it. Leave some for the rest of us.

-- Rio(twenty 50's & counting)Rico

09-02-2010, 06:12 PM   #35
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The 55/1.8 has some very nice attributes(contrast, sharpness, bokeh).
The 50/1.7 is above average in a number of areas(sharpness and wide open performance). However it doesn't come across as special(to me anyways). I've been using mine on a 2x Vivitar macro tele since I've gotten it since I never used it over that of a 50/1.4. Though for what it's worth, I don't think it comes close to the 55/1.8 with respect to bokeh color and sharpness.
09-02-2010, 08:55 PM - 1 Like   #36
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QuoteOriginally posted by paperbag846 Quote
... The question is... why would the K55 has smoother bokeh? Both lenses have 6 aperture blades... is it all focal legnth? Does it have to do with the physical size of the lens (the k55 is larger).
It's mostly to do with spherical aberration, and to what degree this has been corrected within the lens. Here's a useful article:

Bokeh
09-02-2010, 10:51 PM   #37
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Paperbag, which picture is which lens?

-- edit: sorry, I just noticed your explanation
09-03-2010, 06:32 AM   #38
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Do not swap, buy the A50
The 55K is the same SMC55 (M42) and IMHO is the sharpest of the normal pentax lenses from that period.
If you can buy the A50 you'll get the extra IQ and support form the A series but you'll probably not gain much in picture quality

11-03-2010, 10:08 AM   #39
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Hey everyone, I've spent a lot of time with these two lenses so I can give a better comparison (for those who care):

Colour: The K 55's colour is more vintage and significantly less accurate / saturated. This is not always a bad thing, but it does not pop like the 50.

Sharpness: The K55 is sharper than the 50 until f4 ish if you are pixel peeping. The k55 also renders higher contrast, while the 50 is softer and brighter (especially wide open). The difference is similar to the difference between the FA 35 and the DA 35 2.4.

Bokeh: Neither lens has killer bokeh when you stop down, but I tend to prefer the 55 because it is more creamy / better subject isolation. The 50 resembles a impressionistic painting. If the background is complicated, the 50 tends to render a harsh bokeh which can be distracting (but other times can look pretty cool).

Focal length: Seemingly unimportant, but possibly the largest difference between these lenses! Colour and contrast are things one can process with raw. Bokeh is more or less similar, with a slight edge given to the K55. However neither can match a 1.4, from what I have seen. However, the 55 is simply a better portrait lens. It is a little tighter and seems to render differently (smoother) since it is more zoomed in. The transition from in-focus to out of focus is very smooth and, I believe, 3-D. The extra 5mm leads to out of focus circles rendering much larger, which can be smoother.

Now all in all, I still want to keep both. However, this focal length in ASP-C land is very much a portrait length, and for this reason the K55 wins. I believe it wins primarily because it is 55mm over 50mm, and increased center sharpness WITH soft edges and backgrounds. The 50mm seems sharp to a fault when stopped down. I suppose you should consider that since I am looking at this as a portrait lens, my interpretations of the lenses' performance is a little skewed. However, the focal length tends to lend itself to portraiture.

Either way, if you own either lens and are wondering about the other one, be confident that they are more similar then they are different. If you are looking for an inexpensive portrait lens, I don't think you can do much better than the K55 1.8 for sub-50 dollars .

Last edited by paperbag846; 11-11-2010 at 08:45 AM.
11-03-2010, 03:39 PM   #40
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paperbag,
I hope you ended up keeping both the k 55 and A50 lenses? Both are so different and very nice for you to keep both!
11-03-2010, 05:10 PM   #41
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Its the K55 for me all the way. It renders differently to most other smc lenses, its a darker more richer hue. It is also a terrific portrait lens. The A50 feels cheap in comparison build wise and its focussing ring is a step backwards towards chinon territory.

The A50 can do this:



The K55 can do this:



Both are cheap enough to have both I think.. You would miss the 55 more though, I know I did.
11-03-2010, 05:26 PM   #42
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I've decided to keep the A 50 till someone is willing to pay good money for it. My copy is in like-new condition... I don't think the previous owner used it very much if at all. It's a "handy fifty", but no "nifty fifty" . I agree with you on the focusing ring. Mine is very firm and smooth, no wobble, but it's just not as precise as the K55 (270 degrees!).

When I eventually buy a 50 1.4, the A 50 will go. AF would go a long way here, and the softer rendering of the 50 1.4 might be more my cup of tea. The K 55 will stay unless I win the lottery and buy the DA* 55. I really like having both focal lengths.
11-03-2010, 11:29 PM   #43
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I'm thinking about getting the Helios 44 m42 when my birthday comes next month. Should be real close to your k 55.
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