Matching a Pentax 50mm 1.4 lens to a Canon 7D?

kukhuvud

The lens in question is this one: Pentax Super Takumar 50mm f1.4.

I've done a bit of reading on the subject and there appears to be two types of M42 lenses: those that have an Auto/Manual switch (and therefore an aperture pin) and those that don't. I'm really new to this and can't see any difference between the one linked above and any others that I see on ebay or while googling.

That brings me to my question: which lens adapter would you folks recommend someone use in this case? It appears that I have choices, but I'm really uncertain which to choose. Some of the posts I've read hint to the fact that the models with aperture pins are nicer to work with on dslr's because you can turn the aperture dial and immediately see results, rather than having to press the shutter to make the change? That sounds infinitely useful Smile

Thanks for any replies Smile

iangreenhalgh1 · Expire: 2014-01-07

All you need is an M42-EOS adapter with a flange that depresses the aperture pin.

Tons of them on ebay for 4-5 dollars.

kukhuvud · Posted: Thu Sep 01, 2011 4:03 am Post subject:

visualopsins · Expire: 2025-04-11

Welcome kukhuvud!

M42-EOS adapter with flange renders A(uto)-M(anual) switch inoperative. The flange adapter is best for M42 lenses without A-M switch, or for a mix of lenses with and without.

On M42-EOS adapter without flange, lens A-M switch works. In A position, aperture ring has no effect, aperture is always open. In M position, aperture ring operates aperture. i.e. set aperture ring to f/8, focus with switch in A position, switch to M to make photo at f/8.

That Super-Takumar is the rare 8-element version. Buyer is asking top price. The later versions are considered better, the M42 "Super-Multi-Coated", and the M42 "SMC". Both of those are half the buyer asking price for the rare Super.

martinsmith99 · Expire: 2013-11-18

For manual, preset and lenses with A/M switch, either adapter will do, but flangeless is better for A/M switch lenses. For Auto only lenses, you need the flanged adapter.

To be honest, I would get one of each as I suspect you will buy more than one M42 lens.

peterqd · Expire: 2014-01-04

Welcome kukhuvud

I had a major problem with the Super-Takumar 1.4/50 with one flanged adapter. The rear elelement is larger and projects more than most lenses, and the hole inside the flange on this adapter was too small to allow the lens to pass completely through, so it jammed before I reached the infinity stop on the lens. I think for this lens you would be well advised to use a non-flanged adapter and stop it down using the Auto/Manual switch.

I couldn't use that adapter with any of the later S-M-C Takumars either, as they have a projecting lever which jammed on the flange. This meant the lenses couldn't be screwed right home and also prevented adjustment of the aperture dial. I chucked that adapter and bought a non-flanged one.

peterqd · Expire: 2014-01-04

kukhuvud · Posted: Thu Sep 01, 2011 10:16 am Post subject:

kukhuvud · Posted: Thu Sep 01, 2011 10:39 am Post subject:

Thanks, guys, for your replies! I think this is starting to make sense now Smile

Is the A/M switch the lowest ring on this lens, that thin one with the bit that sort of juts out further than the rest? And has a visible 'A' and 'M' on the 3rd and 4th photos? Would this lens therefore be considered an A/M lens? I know these are total newbie questions, but I reckon it's better to make myself look dumb now rather than later Smile

I've been looking at this particular lens because the photos seemed thorough; I do know this price is crazy and certainly wouldn't pay that unless I was desperate! Ok, I'm desperate... but not THAT desperate Razz

Is there a reputable USA seller of the non-flanged adapters on eBay? Or should I bring that over to the Adapters section?

peterqd · Expire: 2014-01-04

OK. M42 lenses which have a pin on the threaded mount are called "Auto" type. This means the aperture blades remain fully open for focussing whatever the aperture setting. When the pin is pushed the blades close to the aperture setting on the dial. Lenses without a pin are manual type, where the blades open and close directly as you turn the dial (or sometimes a separate preset dial).

Most auto lenses have an Auto-Manual switch (A/M) which disconnects the auto pin and converts the lens into a manual type. This was intended so that the lens could be used on older cameras not designed for auto lenses. There are only very few M42 auto lenses which don't have this switch.

Cameras designed to use auto lenses, such as Praktica, some Zenits, earlier Chinons and Pentax Spotmatics, have a bar inside the lens mount which pushes against the pin and closes the blades when you fire the shot. Modern cameras don't have this bar, so you can think of them like the older non-auto cameras, and you have to close the blades manually. The best way to do this is to slide the A/M to Manual setting (the A mark is hidden and the M mark is visible), which disconnects the pin. Alternatively you can use a flanged adapter which keeps the pin permanently pushed in so that it operates like manual mode, but the flange can cause problems as explained earlier.

For M42 to EOS a good source on eBay is the seller "big_is", but there are plenty more. Don't go too cheap or the quality will suffer. I'd suggest you get the unflanged type with AF-confirm chip, which triggers the autofocus beep and flash when you're spot-on focus.

kukhuvud · Posted: Fri Sep 02, 2011 4:49 pm Post subject:

Thanks everyone, for your advice! I really appreciate it Smile

I pulled the trigger yesterday on one of these. I didn't get the 8 element one that I posted here, but rather a 7 element SMC model. It's in beautiful condition and since it's shipping from the San Francisco area, I should have it in my hands on Tuesday!!

With any luck, the m42 ring will ship today as well. It's coming from Utah, but because of the long weekend I might get that on Tuesday as well Smile