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07-25-2010, 03:31 AM   #1
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Difference in bokeh 50mm SMC-A

I just bought an 50mm SMC-A 1.4 on eBay. I have owned both the 2.0 and 1.7 versions but sold them both to buy this one.

Is there a big difference in bokeh on these lenses? Do the 0.3 stop make any difference? I was buying it to get really blurry backgrounds.

Perhaps someone has any sample images?

Per

07-25-2010, 05:36 AM   #2
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QuoteOriginally posted by pyra_ohms Quote
I just bought an 50mm SMC-A 1.4 on eBay. I have owned both the 2.0 and 1.7 versions but sold them both to buy this one.

Is there a big difference in bokeh on these lenses? Do the 0.3 stop make any difference? I was buying it to get really blurry backgrounds.

Perhaps someone has any sample images?

Per
I don't have the 2.0 and 1.7 so I can't tell what is the difference. But here is a sample image taken wide open with A50/f1.4

07-25-2010, 07:09 AM   #3
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It looks great! Another question; How to achieve "bubble-like" backgrounds? Where the bokeh gets really circular?

Per
07-25-2010, 07:56 AM   #4
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QuoteOriginally posted by pyra_ohms Quote
It looks great! Another question; How to achieve "bubble-like" backgrounds? Where the bokeh gets really circular?

Per
That can be achieved with fast lens like the A50/f1.4. Just shoot wide open, find a subject that has several small sources of light in the background - think about small lights on a Christmas tree for example. Just make sure you nail the focus on the foreground subject though.

07-25-2010, 11:07 AM   #5
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QuoteOriginally posted by pyra_ohms Quote
It looks great! Another question; How to achieve "bubble-like" backgrounds? Where the bokeh gets really circular?

Per
you can do it with many lenses, you just must use it wide open (you can however also stop down by half a step). Here i used my A 50 f1.7 at f2, and the oof lights are still quite circular.

07-25-2010, 12:04 PM   #6
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Don't take my post as expertise - merely regurgitating what I have learned here and am just beginning to put into practice.

Generally Pentax K, M and A 50 1/7's and 55/1.8's from Takumar on have a flat field and to be very sharp across the image circle.

The 50/1.4's emphasize the subject by blurring the background. The image field isn't quite so flat nor is the image quite so sharp (though sharp enough) at the edges as the 1.7's. By using the shorter depth of field at wider aperture (and using the less defined edge areas) one can achieve a 3-D effect in the right lighting (though not quite as well as the 43 or 31 Limiteds, of course).

The circularity of the OOF highlights is determined in large part by the number of aperture blades - the more blades, the less angular the intersection between them and the more circular the highlights.

K50/1.2 = 8
A50/1.2 = 9
K50/1.4, M50/1.4, A50/1.4 = 8
All the 50/1.7's and 50/2's, and the K/55's = 6

Incidentally, the A50/1.7, perhaps alone of all Pentax lenses, has a plastic fitting that holds the ball bearing aperture detent in place. The plastic is spot welded at its edges, and the welds often break. For that reason alone I have avoided the A50/1.7, although I have owned a number of M's.

Right now I have SMC Tak, K, A and FA 50/1.4's and 2 different Takumar 55/1.8's. They all produce unique images.

And I don't really have a lot of 50's.
07-25-2010, 01:27 PM   #7
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QuoteOriginally posted by pyra_ohms Quote
It looks great! Another question; How to achieve "bubble-like" backgrounds? Where the bokeh gets really circular?

Per
Yeah wide open or stopped down a little bit and the "buble like" backgrounds can be acheived.

Heres a few with my A50 1.7 @ f.20


07-25-2010, 02:18 PM   #8
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QuoteOriginally posted by TOUGEFC Quote
Yeah wide open or stopped down a little bit and the "buble like" backgrounds can be acheived.

Heres a few with my A50 1.7 @ f.20

Thats what im talking about! Very nice!

07-25-2010, 02:21 PM   #9
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QuoteOriginally posted by monochrome Quote
The circularity of the OOF highlights is determined in large part by the number of aperture blades - the more blades, the less angular the intersection between them and the more circular the highlights.

K50/1.2 = 8
A50/1.2 = 9
K50/1.4, M50/1.4, A50/1.4 = 8
All the 50/1.7's and 50/2's, and the K/55's = 6
So it seems like im going for the second best option here then. Damn, i wish i could afford a F1.2 one..

Per
07-25-2010, 02:38 PM   #10
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Just to muddy the water, don't forget the faster cousin, f1.2 which can give some truly amazing images.

There are many threads on the pros & cons of these fast 50s on this forum, just get one that works for you.
07-27-2010, 01:39 PM   #11
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Maybe sometime I should get together all my 50's and do a test (I swear I didn't mean to end up with so many), but I do have the K50/1.2, a few varieties of the 50mm f1.4's, a pair of the f1.7's, the M50/2, and the SMC Takumar 55mm f1.8 (and the Voigtlander Nokton 58mm f1.4 on the way). I have to say that yes, they do have a somewhat different and distinct look, but all of them are capable of great background blur. I actually like the (S-M-C Takumar) 50mm f1.4 for general use, and I really like the quality of the background it produces wide open, as well as being quite sharp in the plane of focus. My advice to you, since you have the 50/1.4 now, is to save your money and don't get the 50mm f1.2; instead, if you want something a little different or to play more with blur, get a 55mm f1.8 (either a SMC Takumar or the K version); they can be picked up very cheep and have a very different look than the 50mm lenses. Monochrome has given a very good analysis of the various options. I would point out that what monochrome stated is only true (re the number of blades) when stopped down; keep in mind that with each of these lenses when used wide open of course present circular OOF highlights.
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