m42 adapter for auto-mount m42 lens

m42 adapterfor auto-mount m42 lens and genuine pentax m42 adapter
note the added inner ring to work with the diaphragm pinm42 adapterfor auto-mount m42 lens and genuine pentax m42 adapter
Comes with the extra tool like other 3rd party adapter
for dismounting purpose
m42 adapterfor auto-mount m42 lens and genuine pentax m42 adapterLeft: M42 adapter with extra ring to work on auto-mount m42 lens
Right: Genuine Pentax M42 adapter

I bought this adapter from my good friend Alex in http://forum.mslenses.com/ and I asked Alex to charge me the regular he charges for his other clients. I got it shipped for $17.00 from Hong Kong, similarly priced like other 3rd party adapters.

This 3rd party adapter has an important function that is not found in all adapters that I have used. Not even the genuine adapter has the added feature: it works with M42 lens that does not have the A/M switch. When one uses an M42 lens, one has to switch the Auto/Manual diaphragm to manual so that the pin on rear is depressed while allowing the blades and diaphragm to close down for the stop-down metering to work in Pentax dSLR or the other K-mount in SLR cameras.

In the K-mount with KAF2 on Pentax K20D or something similar, what is missing is a mechanism to hold the auto-mount diaphragm governing pin in place for the blades to close down in stop-down metering. And this adapter has the extra ring on the back that is designed to depress the pin down, effectively serve as an M switch in a normal Auto/Manual diaphragm switch. I was quite pleased to try it out on a recent LBA purchase of a Lentar 200mm f/3.5 auto-mount m42 lens. You see the pin on the end in photos next to this paragraph. I have another auto-mount m42 lens that is exactly like this with a pin that all of my Pentax K-mount bodies can't handle the stop-down metering without alternation. There are several ways to do the alternation and the most prominent one has been using tube to place under the pin to shorten the pin which allow the diaphragm to go freely upon stop-down metering.

The new adapter from Alex works extremely well for the auto-mount lens that I have just purchased. There is no known label on the adapter and I will share my experience with the adapter when time allow. So far, it has work quite well for me when I mount it on 2 lens: one lighter with a 35mm f/2.8 and one quite heavy with my new Lentar 200mm auto-mount M42 lens. The later one misses the switch for Auto/Manual diaphragm switch. And the adapter comes in handy for my use.

Inner ring will depress the diaphragm pin correctly
serve to switch the m42 to Manual diaphragm
m42 adapterfor auto-mount m42 lens and genuine pentax m42 adapter
Impressions & Notes
  • Mounting is exactly the same mechanics as the genuine and 3rd party adapters

  • The extra inner ring is designed to work with auto-mount diaphragm m42 lens without the Auto/Manual (A/M) switch that are found in most M42 lens. Some older version of M42 lens seem not to have the A/M switch and by default they go into Auto-diaphragm which will yield problems for Pentax dSLR with KAF2 mount.

  • The adapter comes with dismount or removal tool similar to Bower or other 3rd party adapter

  • The machining on the adapter can be improved. I will communicate to Alex to see if the machining on the metal edges on the adapter can smoothed out with finer edges.

  • Though the adapter comes with removal tool, I found myself very surprised that I can actually dismount the adapter using my two fingers as shown in next picture. This is a big feature not to be missed for those auto-only m42 lens that don't have the A/M switch for auto and manual diaphragm settings.

    m42 adapterfor auto-mount m42 lens and genuine pentax m42 adapterI can dismount with two fingers
    similar to genuine m42 adapter

  • I need to test it more. But as of my first impression, the adapter works beautifully for two m42 lenses that I tried. It work well with the auto-mount m42 lens

  • m42 adapter with inner flange -- mflenses forum member hk300
  • alexcwyuen@hotmail.com -- email contact
  • Disclaimer: I don't endorse the product as I generally recommend the use of genuine Pentax m42 adapter. This adapter has one unique feature with the inner flange that helps to work with auto-mount m42 lenses that lack the A/M switch. The inner flange depresses the aperture pin making it manual diaphragm as in switching to M in the A/M switch.



Sid said...

"from my good friend Alex in mflense.forum.com"

You mean forum.mslenses.com, right? ;)

Hin Man said...

Yes, thank you for the correction. I will later find the link that Alex sells this ring through his connection to the wonderful moderator, likely the owner or founder of http://forum.mflenses.com who help Alex to sell the adapter in ebay.

Disclaimer: I am a good friend of Alex whom I met in mflenses.com. I am yet to put the adapter to go through more serious use on normal m42 lens and those without A/M switch that work as auto-mount m42 lenses.

stanleyk said...

Thanks! I really want/need one of these.

Your blog is really great. I am of course a chronic lens buyer so I like to read what other people's experiences are. Your commentary is very helpful. I discovered it from the Pentaxdslrs site. Much better than the Pentax forum. Too much pixel peeping arguing and RiceHigh/Samsungian churlishness over there.

Hin Man said...

@Stanleyk, thank you for the comment and visit. I am yet to test out the adapter with more serious use. I found that it is not as sturdy as the genuine adapter in that it does not hold a heavy lens well and I can easily overturn in mounting and that seems a bigger problem not noted in my initial test, I will hopefully update soon along with some request to Alex for a more secure plate for holding heavier lens.

Somanna said...

I did not there was such an adapter out there... interesting.

Anonymous said...

Link to source for this adapter?

Hin Man said...

I finally manage to find the link to the M42 adapter that was discussed in mflenses forum

mflenses forum on M42 adapter by hk300

And the email to contact the seller is alexcwyuen@hotmail.com

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