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03-21-2013, 05:50 AM - 3 Likes   #1
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Pentax-M 50mm f1.4 at f1.4 sharpness fix

I was initially somewhat sceptical, but using a 49-28mm step-down ring as a lens hood, as suggested by SOldBear, here, really works.

K-7 with a Pentax-M 50mm f1.4 fully open. It is much sharper with the step-down ring hood.

Same exposure and post-processing on both. Full sizes are on Flickr.







03-21-2013, 06:18 AM   #2
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Yes, contrary to a widespread preconception, the Pentax M/A/FA 50mm f1.4 series is quite sharp wide open, but sharpness at f1.4 cannot be achieved without a hood with these lenses.
03-21-2013, 06:47 AM   #3
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QuoteOriginally posted by kh1234567890 Quote
Pentax-M 50mm f1.4 at f1.4 sharpness fix
Your case is proven my Lord, it just goes to show what a good lens hood can do.

I'm already the converted, I use them on everything, also for good lens protection as well.
03-21-2013, 06:56 AM   #4
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Wow, quite a difference!
Do you guys think it would be useful for my F 50mm 1.7, considering the front element is a bit recessed already, and i'm using a lens hood for 50mm lenses in fullframe?

03-21-2013, 07:15 AM   #5
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Mind blown.
03-21-2013, 07:24 AM   #6
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QuoteOriginally posted by GabrielFFontes Quote
Do you guys think it would be useful for my F 50mm 1.7, considering the front element is a bit recessed already, and i'm using a lens hood for 50mm lenses in fullframe?
In my experience a lens hood is never a bad thing and can only help to render things equal or better. In bright situation, yes, a hood helps, specially if sun light hit directly the front lens element
03-21-2013, 07:36 AM   #7
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Thanks for the info and the link back to the previous post ... J
03-21-2013, 08:03 AM   #8
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QuoteOriginally posted by GabrielFFontes Quote
Wow, quite a difference!
Do you guys think it would be useful for my F 50mm 1.7, considering the front element is a bit recessed already, and i'm using a lens hood for 50mm lenses in fullframe?
There might be some improvement at f1.7, but nowhere as dramatic as with the 50/1.4 lens at f1.4. It's the optical construction of the M/A/FA 50/1.4 that calls for a hood. It's ironic, but people choose to buy the much heavier Sigma 50mm 1.4 on account of the FA's alleged softness wide open, when a cheap and light rubber hood makes all the difference--which actually many PF reviews, including mine, clearly indicate.

03-21-2013, 08:15 AM - 1 Like   #9
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QuoteOriginally posted by causey Quote
There might be some improvement at f1.7, but nowhere as dramatic as with the 50/1.4 lens at f1.4. It's the optical construction of the M/A/FA 50/1.4 that calls for a hood.
I think that in this case stray light bouncing around the sensor box was the main problem. The reducer 'hood' vignettes the image just to the APS sensor area. I've tried conventional hoods with this lens, including home-made black card ones, but the effect was never this drastic.
03-21-2013, 08:55 AM   #10
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QuoteOriginally posted by kh1234567890 Quote
I think that in this case stray light bouncing around the sensor box was the main problem. The reducer 'hood' vignettes the image just to the APS sensor area. I've tried conventional hoods with this lens, including home-made black card ones, but the effect was never this drastic.
I just read SoldBear's post: the idea is awesome. Buying step-down rings for my lenses right now! Thanks for posting this.
03-21-2013, 09:39 AM   #11
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There also seems to be less CA. I suppose that's normal expectations for a lens hood, but still a bonus!

Side Note: 49->28mm+28mm lens hood = Better results potentially?(Well, in theory?)
03-21-2013, 09:57 AM   #12
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AMAZING! I just bought an A50/1.4 for cheap and was about to sell it since I have a F50/1.7... will give this a try. thanks
03-21-2013, 10:16 AM   #13
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I read that in early days, apertures were placed in front of lenses. They do not vignette, they act to stop down.
As well as acting as a (probably more efficient) hood, for a 50 mm lens with a 28 mm hole in the adaptor ring, the lens has a new f/ number of 50/28 = f/1.8
I will try this on a f/2 50 mm
03-21-2013, 10:38 AM   #14
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I can't find a 49mm to 28mm step down ring.... =(
03-21-2013, 10:49 AM   #15
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QuoteOriginally posted by ChrisTrevino Quote
I can't find a 49mm to 28mm step down ring.... =(
I got my step-down ring from here. Turned up in 6 days. Not bad for 2 ($3).
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