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06-09-2010, 09:49 PM   #1
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Pentax K 55mm F/1.8 Lens Test

Hello Guys,
Although I am fairly new to this site, I enjoy the endless first hand information I find here. I figure I should pull my own weight, so I decided to do a lens test for the Pentax k 55m f/1.8. This is the first lens I bought for my k-x after the kit lens. I thought that with the crop factor, a 55mm lens could make an affordable portrait lens (I believe its like a 82-83mm lens now). I bought it from ebay for 80 dollars. The seller said it was in near mint condition but when I received it yesterday, there were obvious marks on the rear element. WEIRD THING is that this lens uses mostly half stops but I didnt understand why it goes from f/1.8 to f/2.8. F/1.8 is a half stop from F/2 but F/2 is a full stop from F/2.8. I put it as F/2 but I cant say for sure.

I did a sharpness test, DOF test, and some test shots with a friend of mine at f/1.8. The sharpness and DOF tests were with a tripod and remote release to remove any human error. Also I used a hood at all times to give the lens a fighting chance. Now this is an old lens so I was only able to use it in M mode and used my incidental Minolta flashmeterIV since the camera meter was horribly off. I dont have a focus prism screen so I did portrait shots by eye and with help of the beep and green thing. All the shots were not edited except for the sharpness ones.

Sharpness Test: I used a book to test the center and corner sharpness. Here all shots were put to 80 sharpness on Adobe raw editor. These are all 205% crops of the originals.


@f/1.8 Center

@f/1.8 Corner

@f/2 Center

@f/2 Corner

@f/2.8 Center

@f/2.8 Corner

@/f4 Center

@f/4 Corner

@f/5.6 Center

@f/5.6 Corner

@f/8 Center

@f/8 Corner

@f/11 Center

@f/11 Corner

@f/16 Center

@f/16 Corner

@f/22 Center

@f/22 Corner

F/1.8 is good at the center but very soft at the corner as expected. F/2 is better in the corners but I recommend nothing faster then f/2.8 for corners. From the test it appears that this lens is sharpest at f/8 all around.

DOF: No corrections. I decided not to use all the F stops since most people only want to see thin DOF. I also skipped the half stop from F/1.8 to F/2.8 and went straight to F/2.8

@f/1.8

@f/2.8

@f/4

@f/5.6

@f/8

At f/1.8 The depth of Field is nothing ridiculous but still somewhat impressive. If any of you read the words in the book and find it interesting, the book is called The Forgotten War.

Field Test: All of these shots were at f/1.8 with lens hood. None of these shots here were edited at ALL. Two shots indoor were at 800iso and the outside shot was at 1600iso. These are all compressed jpegs which lose some quality and dont do the originals ANY justice(especially her red-orange hair).




The first shot really shows the 3-D effect this lens is capable of and is worth buying on that alone in my opinion. The last shot shows the lens bokeh and I think it looks nice. I thought becuase of the 6 blade aperture, the bokeh would be more hexagonal but instead its circular.

My Final Opinion:
This lens is a tremendous competitor as a portrait lens. Considering that this lens has some dust and a large mark on the rear element, I was very impressed. I have the ability to return this lens tomorrow since the seller mislabeled it, but I think I will keep it! The manual focus does make it harder to focus, but Ive only had this lens for 24 hours and Ive gotten some very nice results(I also have a viewfinder magnifier too :S). With practice you WILL get better, but a VF magnifier, focus screen and focus confirmation beep help alot. Aperture priority doesn't work so you might want to take the dust off your Incidental meter. The corners are soft until f/4-f/5.6 but ill probably never stop down to that since I only want to use it for natural light portraits. PLUS its 3 and a half STOPS FASTER then the kit lens. If you can buy this lens for 50 dollars, I highly recommend it!

I hope you all enjoyed my first review. Please feel free to critic my review here, and I'd be very interested in feedback and other people who own this lens. If you would like to see the edited versions of the photos of my friend, then please go to flickr.com/zurinaga . I will add them soon

06-09-2010, 11:14 PM   #2
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Very good effort! - thx
I own this lens too, as well as the f2 version.
TBH. I find the 55/2 to hold detail a little longer in the arperture than the 55/1.8
Which is really odd tbh, but I think that's just variance bewteen copies.

All in all, I really like them(seem sharper than my 50's).
And the K's were a blessing to replace the old SMC Tak 55/1.8 which reguired an adapter etc.

But... ... I think, my HELIOS 44-7 is even sharper than my K 55's
Though the only way to really know will be to roll up my sleves and take your example. Put them head to head.
06-10-2010, 12:27 AM   #3
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QuoteOriginally posted by JohnBee Quote
Very good effort! - thx
I own this lens too, as well as the f2 version.
TBH. I find the 55/2 to hold detail a little longer in the arperture than the 55/1.8
Which is really odd tbh, but I think that's just variance bewteen copies.

All in all, I really like them(seem sharper than my 50's).
And the K's were a blessing to replace the old SMC Tak 55/1.8 which reguired an adapter etc.

But... ... I think, my HELIOS 44-7 is even sharper than my K 55's
Though the only way to really know will be to roll up my sleves and take your example. Put them head to head.
JB, I don't think you would mind which lens is sharper and would think it's quite close with the Helios edging out the Pentax slightly. although the Pentax's sharpness wide open works pretty well and wouldn't consider it as a weakness but rather a unique asset.
06-11-2010, 12:37 AM   #4
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Original Poster
QuoteOriginally posted by JohnBee Quote
Very good effort! - thx
I own this lens too, as well as the f2 version.
TBH. I find the 55/2 to hold detail a little longer in the arperture than the 55/1.8
Which is really odd tbh, but I think that's just variance bewteen copies.
Thank you. I've heard that the 1.8 and 2 versions are optically identical, but it seems like every lens is different I hunted down this lens exactly because I didn't want to get an adapter for the m42 lens.

Id definitely liked to see that lens tested to see how they stack up because I know little of that lens.I must say though that in a nerdy way I had a lot of fun doing this.

06-11-2010, 05:52 PM   #5
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First a question to the OP...Did you get any compensation back from the seller in regards to the rear element scratch. Scratches are usually pretty well tolerated on the front element, but can affect performance when on the rear element. The $80 price you paid is premium. With the scratch, the value would be less than $30 in my book. I paid $48 for my K 55/1.8 this time last year in Ex condition and pristine glass.

In regards to the K 55/1.8 in general...It is a really great lens in my opinion. I have quite a few fast 50s and it is the best all-round lens of the bunch...reliably sharp with good color rendition and bokeh, it is a true winner. The next best in my bag (as noted above) is the Helios 44M due to its beautiful bokeh and center sharpness. It should be noted that the Helios is not that great on 35mm film. While edge sharpness is adequate on APS-C for the Helios, it really sucks with the larger format.


Steve
06-12-2010, 03:35 PM   #6
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Im sorry, if I said scratches I meant a scuffy looking smudge, but then I wiped it with a lens tissue and warm breath and it disappeared. I thought it could have been a scratch since he mailed it without a rear cap albeit wrapped in bubble rap. This seller is alread getting negative feedback since he also didnt find it convenient to communicate with me at all during the process.

I know very little about he 44m but it seems like a fan favorite, despite its m42 mount. I guess its better then the super Takumar?
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