Found a Pentax Sears A 75-300mm F4.5 for $40 and a 50mm M/1.4 for $30

**Clinton** · 03-27-2010, 05:02 PM

In an adventure today, I stopped by some pawn shops here in Salt Lake and spent the time to dig through their lenses when I happened upon a like new Sears K mount lens with an A setting on the aperture ring. It was closed away in a padded leather hard case, and looks as though it's never even been used.

When they told me they wanted $40 for it, I rushed out to my car, got my K-7, hooked it up and was astounded that it was working flawlessly.

On the lens, it reports 1:4.5-5.6; therefore the next surprise was when I zoomed it out to 300mm the lens still reported it was F4.5. Is this a mistake on the lens's reporting to the camera or is it really F4.5 through the whole range? The metering doesn't appear to underexpose at 300mm F4.5.

I'll try to post some pics of the lens and with the lens tomorrow. Right now I need to hook our 1.7x tc to it and see what it looks like.

On this same trip at a later pawn shop, I picked up a Pentax-M 50mm F1.4 for $30!

forensicscientist · 03-27-2010, 05:10 PM

Nice find. I've visited many a pawn shop in search of a "find". Never found any photo gear...but once found a carbon frame bike (cycling is my other passion), complete with exceedingly high end wheels, and other parts for only $300. I quickly paid and left....all the while feeling like I had just robbed them......and basically I did.

**Just1MoreDave** · 03-27-2010, 06:30 PM

Originally posted by cgoudie

...On the lens, it reports 1:4.5-5.6; therefore the next surprise was when I zoomed it out to 300mm the lens still reported it was F4.5. Is this a mistake on the lens's reporting to the camera or is it really F4.5 through the whole range? The metering doesn't appear to underexpose at 300mm F4.5.

The original method for A series lenses to tell the camera their maximum aperture could only handle one aperture value. So all variable-aperture A-type zooms behave this way. The method uses a pattern of contacts on the mount to communicate with the camera. Besides telling only one aperture to the camera, they can only say whether the aperture ring is in the A position or not.

Autofocus lenses like the F series have a chip and communicate more data digitally. Variable aperture zooms work in this system, which can also send focal length for SR to work and the lens name. The FA chips added more capacity so FA lenses have more data, and DA lenses even more. Third party lenses may have less information, either because they did not license the mount from Pentax or Pentax added more data without officially changing the published specs.

03-27-2010, 05:02 PM	#1
Clinton Site Supporter Join Date: Feb 2010 Location: Salt Lake City, UT Photos: Gallery \| Albums Posts: 1,910	Found a Pentax Sears A 75-300mm F4.5 for $40 and a 50mm M/1.4 for $30 In an adventure today, I stopped by some pawn shops here in Salt Lake and spent the time to dig through their lenses when I happened upon a like new Sears K mount lens with an A setting on the aperture ring. It was closed away in a padded leather hard case, and looks as though it's never even been used. When they told me they wanted $40 for it, I rushed out to my car, got my K-7, hooked it up and was astounded that it was working flawlessly. On the lens, it reports 1:4.5-5.6; therefore the next surprise was when I zoomed it out to 300mm the lens still reported it was F4.5. Is this a mistake on the lens's reporting to the camera or is it really F4.5 through the whole range? The metering doesn't appear to underexpose at 300mm F4.5. I'll try to post some pics of the lens and with the lens tomorrow. Right now I need to hook our 1.7x tc to it and see what it looks like. On this same trip at a later pawn shop, I picked up a Pentax-M 50mm F1.4 for $30!

03-27-2010, 05:10 PM	#2
forensicscientist Pentaxian Join Date: Jun 2008 Location: DFW Texas and Michigan - I commute :) Posts: 1,012	Nice.... Nice find. I've visited many a pawn shop in search of a "find". Never found any photo gear...but once found a carbon frame bike (cycling is my other passion), complete with exceedingly high end wheels, and other parts for only $300. I quickly paid and left....all the while feeling like I had just robbed them......and basically I did.

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03-27-2010, 06:30 PM	#3
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	Originally posted by cgoudie ...On the lens, it reports 1:4.5-5.6; therefore the next surprise was when I zoomed it out to 300mm the lens still reported it was F4.5. Is this a mistake on the lens's reporting to the camera or is it really F4.5 through the whole range? The metering doesn't appear to underexpose at 300mm F4.5. The original method for A series lenses to tell the camera their maximum aperture could only handle one aperture value. So all variable-aperture A-type zooms behave this way. The method uses a pattern of contacts on the mount to communicate with the camera. Besides telling only one aperture to the camera, they can only say whether the aperture ring is in the A position or not. Autofocus lenses like the F series have a chip and communicate more data digitally. Variable aperture zooms work in this system, which can also send focal length for SR to work and the lens name. The FA chips added more capacity so FA lenses have more data, and DA lenses even more. Third party lenses may have less information, either because they did not license the mount from Pentax or Pentax added more data without officially changing the published specs.