What filter thread size does the Pentax-M 50mm f/2 use for a reversing ring on a Canon 450D?
Asked 10/1/2012
2 views
2 answers
0
I want to use an SMC Pentax-M 50mm f/2 as a reversed macro lens on my Canon EOS 450D. The lens cap says 49mm, but the front of the lens says 50mm, so I’m unsure which reversing ring size I need. Will a 49mm Canon EOS reversing adapter work for this lens? I also already have a 58mm reversing ring for my Canon EF-S 18-55mm lens.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
5
To get a smaller threaded lens to work with a 58mm adaptor just requires the appropriate stepping ring. You can get an entire set of these for not much money, or you can measure the lens to find out exactly which size you need (my money would be on the value stated on the lens itself to be the correct one):
http://www.amazon.co.uk/Fotodiox-Anodized-49-52mm-52-55mm-55-58mm/dp/B001G445Q4
You can also use your 18-55 stopped down if you hold down the depth of field preview button then unmount the lens, this will leave the iris set to whatever value the camera was set to.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
13y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. For the Pentax-M 50mm f/2, the 50mm marking is the focal length, not the filter thread size. The filter thread for that lens is 49mm, so a 49mm Canon EOS reversing ring should fit.
If you want to use your existing 58mm reversing adapter with a smaller-thread lens, you can also use a step-up ring.
For your EF-S 18-55mm, there is a workaround to set the aperture before reversing: mount the lens normally, choose the aperture in aperture-priority mode, press and hold the depth-of-field preview button, and then unmount the lens while holding it. This leaves the aperture stopped down until the lens is reattached. Be aware that smaller apertures will require more light.
Recommended products
UniqueBot
AI13y ago
Your Answer
Related Questions
Why does my Canon 18-55mm lens look gray and blurry when used reversed?
Can I use 58mm filters on Sony NEX-7 lenses that take 49mm filters?
Manual-focus ring jammed after dropping a Pentax ME Super lens
Can old Pentax K manual-focus lenses be used on a modern Pentax DSLR, and will autofocus work?
Can Pentax K-mount lenses be used on a Canon AE-1?