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05-28-2010, 11:55 AM   #1
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The K 55mm 1:1.8 - worth having with the M 50mm 1:1.7?

I posted this in the K club thread but reckoned Id get more responses in a separate thread. Thanks to "gofour3" for his contribution there, Ive pasted it below in case anyone else wants to comment.

So, I can get a good condition bayonet mount 55mm F1.8 at a reasonable price, but am debating if it will bring me anything over the M 50/1.7 that I currently have. Its appealing due to the slight extra length that brings it to 82.5mm on APS-C.

The 55 is slightly longer but apparently reasonably sharp enough wide open, and deadly sharp stopped down a couple, which is good, but does it suffer from colour fringing? My M 50 suffers a bit from this. Is the K sharper than the M?

The K55 seems to have some nasty, funky bokeh at times too, which Im concerned about. Ive found plenty of pics taken with it online, but because its manual its often impossible to know the aperture value used.

Extra weight or size does not bother me, though the 52mm filter thread will be a pain as my four M lenses are all 49mm. If its better built (there are lenses better bult than Ms??? ) then thats definitely a worthwhile compromise.

Opinions? What would this lens bring me?

Many thanks for any help offered.

From "gofour3":

I dont shoot digital, but on film the K55/1.8 is a perfect lens that does not suffer from fringing or any other issues. Its also a bargain price wise compared to other Pentax lenses in this FL range. The K55/1.8 is also better built than the M50/1.7, but it's also heavier.

05-28-2010, 12:08 PM   #2
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I used to have F50/1.7 and for a very short while A50/1.7 and I decided to keep the K55/1.8.
Those extra 5mm do make some difference in framing, which matters...at least to me
Opticaly I believe the Pentax 50/1.7 and 55/1.8 & 55/2 are identical.
Built quality wise, K series is pretty much unmatched by anything but FA ltds (if).
In my opinion get K55/1.8 and sell M50/1.7 and get either 50/1.4 or 1.2 if you need faster lens.
Another point is, gofour is right in terms of price K55 is a steal, financially it would make sense to get K55 and sell M50, not a big profit but some....
filter wise, I think step down ring from 52>49 would be OK since you would use the lens on digital.

my 2p
05-28-2010, 01:20 PM   #3
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my opinion regarding the 2 lenses is that the 1.7's bokeh at times can be distractingly harsh or busy. the 1.8 however is pretty consistent with regards to bokeh and very smooth as well as long as you shot wide open or avoid shooting some background highlights when stepped down. I'm not sure why you said that it has some nasty and funky bokeh though.

if I would simplify the criteria for both lenses I would say:


50/1.7

sharp wide open
a bit cool color tone
a bit of fringing
good bokeh (sometimes can be harsh)
all-purpose lens

K55/1.8

moderate sharpness wide open
a bit warm color tone
lack of fringing 9 as far as I can tell
great bokeh wide open (avoid shooting specular highlights when stopped down)
excellent portraiture lens
05-28-2010, 01:26 PM   #4
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The K 55 is superior in every way.

Better build.
Better resolution(both naively and at higher aperture f/9 to11).
Better resistance to flair.
Better contrast.
Better Bokeh.

Also it appears the K 55 2.0 holds out a bit longer on resolution than the f/1.8 version according to takinami.

05-28-2010, 01:32 PM   #5
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thanks JB, I forgot to mention about the K55's resolution. it really has a great resolution indeed.
05-28-2010, 02:01 PM   #6
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QuoteOriginally posted by Jonathan Mac Quote
Opinions? What would this lens bring me?
Trouble.

You might think now that you will simply acquire the K55/1.8, spend a day swapping with the M50/1.7, then sell the loser. Then you will decide both are nice and inexpensive, selling one would only gain me $xx, might as well keep them. You end up liking both.

In July, you'll see an F50/1.7 for $180. Ooooh, autofocus! An A position on the aperture ring! Better snap that up, it's a great price. You should definitely sell... something. No one needs three lenses that are that close in performance. Except the M is so nice to manually focus, the K is even better, and wow, the F really sucks. And the M looks good on that film body that just showed up looking for a home...
05-28-2010, 02:16 PM   #7
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QuoteOriginally posted by Just1MoreDave Quote
Trouble.

You might think now that you will simply acquire the K55/1.8, spend a day swapping with the M50/1.7, then sell the loser. Then you will decide both are nice and inexpensive, selling one would only gain me $xx, might as well keep them. You end up liking both.

In July, you'll see an F50/1.7 for $180. Ooooh, autofocus! An A position on the aperture ring! Better snap that up, it's a great price. You should definitely sell... something. No one needs three lenses that are that close in performance. Except the M is so nice to manually focus, the K is even better, and wow, the F really sucks. And the M looks good on that film body that just showed up looking for a home...
Ha ha ha!! I am already becoming familiar with LBA & Ive only had an SLR for a year! Im sure I wont sell the M 50 even if I get the K, unless I replace it with an F1.4 or an A lens later on.

As for nasty bokeh, check the user reviews section of this site (Pentax Lens Review Database - SMC Pentax 55mm F1.8 Lens Reviews) & you will see three pics from jsherman999. The first one has the most horrendous bokeh Ive ever seen. The other two photos are beautifully sharp with great colours.
05-28-2010, 02:53 PM   #8
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QuoteOriginally posted by Just1MoreDave Quote
Trouble.

You might think now that you will simply acquire the K55/1.8, spend a day swapping with the M50/1.7, then sell the loser. Then you will decide both are nice and inexpensive, selling one would only gain me $xx, might as well keep them. You end up liking both.

In July, you'll see an F50/1.7 for $180. Ooooh, autofocus! An A position on the aperture ring! Better snap that up, it's a great price. You should definitely sell... something. No one needs three lenses that are that close in performance. Except the M is so nice to manually focus, the K is even better, and wow, the F really sucks. And the M looks good on that film body that just showed up looking for a home...
That is how over the past 15 years I've ended up with 8 renditions of the 55mm Tak, S.T. 50mm and s-m-c 50mm, A 50mm f1.2, FA 50mm f1.4, with a 58mm f2 Russian lens hanging off on the side somewhere. That doesn't even count some other random 50s. :Hysterical: Some of those deals only the transport company came out ahead, but I doubt that because I live in the woods.

05-28-2010, 07:13 PM   #9
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I own both lenses and here is my take:
  • The K 55/1.8 is better optically and is my most capable "fast 50" out of the 10 or so lenses at the focal length that I own
  • The M 50/1.7 is almost as good optically and is smaller and lighter
  • Build is equivalent between the two
  • The K55/1.8 has a wider focus ring
I use the K55/1.8 on my KX (film) and K10D where weight and size are less of an issue. I use the M 50/1.7 on my light/small Ricoh XR7 film body. I like Dave's advice...use both for a while and sell the one that you like less. The value of both lenses is close to the same with the K 55/1.8 bringing a somewhat higher price. I paid $48 for mine about a year ago.


Steve

FWIW...my favorite "fast 50" for digital is that cheap Russian 58/2...yep, the Helios 44M still reigns...

Last edited by stevebrot; 05-28-2010 at 07:53 PM.
05-28-2010, 07:51 PM - 1 Like   #10
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QuoteOriginally posted by axl Quote
...Those extra 5mm do make some difference in framing, which matters...at least to me...
Yes, the extra 5mm do make a difference in framing.

QuoteOriginally posted by axl Quote
...Opticaly I believe the Pentax 50/1.7 and 55/1.8 & 55/2 are identical...
The optics in the K 55/1.8 are similar, but not identical to those in the M 50/1.7. The M 50/2 is quite different with five rather than six elements. The K55/1.8 and K55/2 have identical optics.


Steve
05-28-2010, 08:14 PM   #11
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That describes my situation...

First started with a K55/1.8, and then bought an A50/1.7 because wanted electronic aperture control. The A50/1.7 has been spending a lot of time on the camera, but I'm about to get an FA50/1.4 for autofocus. I'm afraid I will not be able to bring myself to sell the A50 since I like MF and it didn't cost me too much.

As others have stated the extra 5mm doesn't seem like much but does make a significant difference in the framing. However, I just prefer the A50/1.7 because its color/contrast is better to my eye, and I can control aperture by the camera dial.

QuoteOriginally posted by Just1MoreDave Quote
Trouble.

You might think now that you will simply acquire the K55/1.8, spend a day swapping with the M50/1.7, then sell the loser. Then you will decide both are nice and inexpensive, selling one would only gain me $xx, might as well keep them. You end up liking both.

In July, you'll see an F50/1.7 for $180. Ooooh, autofocus! An A position on the aperture ring! Better snap that up, it's a great price. You should definitely sell... something. No one needs three lenses that are that close in performance. Except the M is so nice to manually focus, the K is even better, and wow, the F really sucks. And the M looks good on that film body that just showed up looking for a home...
05-28-2010, 08:40 PM   #12
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QuoteOriginally posted by Jonathan Mac Quote
Ha ha ha!! I am already becoming familiar with LBA & Ive only had an SLR for a year! Im sure I wont sell the M 50 even if I get the K, unless I replace it with an F1.4 or an A lens later on.

As for nasty bokeh, check the user reviews section of this site (Pentax Lens Review Database - SMC Pentax 55mm F1.8 Lens Reviews) & you will see three pics from jsherman999. The first one has the most horrendous bokeh Ive ever seen. The other two photos are beautifully sharp with great colours.
you have to check the exif on that image. it is probably shot at a slower shutter speed and windy situation. and if you would read carefully, it's not even the K55/1.8 but a SuperTak 55/1.8.
05-28-2010, 10:38 PM   #13
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QuoteOriginally posted by Pentaxor Quote
... if you would read carefully, it's not even the K55/1.8 but a SuperTak 55/1.8.
I think it is a K55/1.8 and with "This is the Super Tak 55 1.8 without the need for an adapter" Jay simply wants to express that the K55/1.8 saves you the trouble of using an adapter but otherwise is identical to the Super Tak 55/1.8.
05-28-2010, 11:48 PM   #14
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QuoteOriginally posted by Class A Quote
I think it is a K55/1.8 and with "This is the Super Tak 55 1.8 without the need for an adapter" Jay simply wants to express that the K55/1.8 saves you the trouble of using an adapter but otherwise is identical to the Super Tak 55/1.8.
whoops, sorry about that. didn't read it too well.

anyway, as I said prior, he might want to know the exif on that image. it does seem to be uncharacteristic of the K55/1.8.
05-29-2010, 12:01 AM   #15
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QuoteOriginally posted by stevebrot Quote
The optics in the K 55/1.8 are similar, but not identical to those in the M 50/1.7. The M 50/2 is quite different with five rather than six elements. The K55/1.8 and K55/2 have identical optics.


Steve
thanks for correcting Steve.

For some reason I have always been under the impression that 55/1.8(2.0) share the optical formula with later 50/1.7 design... oh well, you learn something new every day
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