Pentax-M 50mm f1.4 at f1.4 sharpness fix

kh1234567890 · 03-21-2013, 05:50 AM - **3 Likes**

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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.

causey · 03-21-2013, 06:18 AM

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.

**Kerrowdown** · 03-21-2013, 06:47 AM

Originally posted by kh1234567890

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.

GabrielFFontes · 03-21-2013, 06:56 AM

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?

tromboads · 03-21-2013, 07:15 AM

Mind blown.

aurele · 03-21-2013, 07:24 AM

Originally posted by GabrielFFontes

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

Jean Poitiers · 03-21-2013, 07:36 AM

Thanks for the info and the link back to the previous post ... J

causey · 03-21-2013, 08:03 AM

Originally posted by GabrielFFontes

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.

kh1234567890 · 03-21-2013, 08:15 AM - **1 Like**

Originally posted by causey

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.

causey · 03-21-2013, 08:55 AM

Originally posted by kh1234567890

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.

Eulogy · 03-21-2013, 09:39 AM

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?)

carrrlangas · 03-21-2013, 09:57 AM

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

wombat2go · 03-21-2013, 10:16 AM

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

ChrisTrevino · 03-21-2013, 10:38 AM

I can't find a 49mm to 28mm step down ring.... =(

kh1234567890 · 03-21-2013, 10:49 AM

Originally posted by ChrisTrevino

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).

03-21-2013, 05:50 AM - 3 Likes	#1
kh1234567890 Veteran Member Join Date: Sep 2010 Location: Manchester, UK Photos: Gallery Posts: 2,653	Pentax-M 50mm f1.4 at f1.4 sharpness fix Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. 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.

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03-21-2013, 06:18 AM	#2
causey Veteran Member Join Date: Feb 2009 Location: Arlington, VA Photos: Albums Posts: 3,757	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
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,819	Originally posted by kh1234567890 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
GabrielFFontes Veteran Member Join Date: Jul 2011 Location: Rio de Janeiro, Brazil Posts: 647	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
tromboads Veteran Member Join Date: Apr 2012 Location: Melbs Photos: Gallery Posts: 1,240	Mind blown.

03-21-2013, 07:24 AM	#6
aurele Veteran Member Join Date: Jan 2011 Location: Paris, France Photos: Albums Posts: 3,217	Originally posted by GabrielFFontes 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
Jean Poitiers Pentaxian Join Date: Apr 2011 Location: Lost in translation ... Photos: Gallery \| Albums Posts: 18,076	Thanks for the info and the link back to the previous post ... J

03-21-2013, 08:03 AM	#8
causey Veteran Member Join Date: Feb 2009 Location: Arlington, VA Photos: Albums Posts: 3,757	Originally posted by GabrielFFontes 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
kh1234567890 Veteran Member Join Date: Sep 2010 Location: Manchester, UK Photos: Gallery Posts: 2,653 Original Poster	Originally posted by causey 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
causey Veteran Member Join Date: Feb 2009 Location: Arlington, VA Photos: Albums Posts: 3,757	Originally posted by kh1234567890 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
Eulogy Veteran Member Join Date: Feb 2012 Location: Fredericton, New Brunswick Photos: Gallery Posts: 632	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
carrrlangas Veteran Member Join Date: Mar 2012 Location: Joensuu (Finland) Photos: Gallery Posts: 1,761	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
wombat2go Veteran Member Join Date: Jan 2010 Location: Michigan Photos: Gallery Posts: 2,207	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
ChrisTrevino Senior Member Join Date: May 2012 Location: Ecorse, MI Photos: Gallery Posts: 123	I can't find a 49mm to 28mm step down ring.... =(

03-21-2013, 10:49 AM	#15
kh1234567890 Veteran Member Join Date: Sep 2010 Location: Manchester, UK Photos: Gallery Posts: 2,653 Original Poster	Originally posted by ChrisTrevino 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).