Sluggish aperture

I have just received an SMC Pentax-M Macro f4 100mm that has nice clean aperture blades but they are extremely sluggish when operating the lever manually. With the lens on camera, I am unable to get anything smaller than an 5.6 opening. Any suggestions as to what my options may be?

Thanks

Drew Peabody

Hi Drew,

you don't say where you bought it. If from a reputable dealer, take it straight back and explain the problem. If from ebay or similar check the exact wording of the ad, making sure that it doesn't say "sold as seen" or similar. If it doesn't, and they have a return/complaints policy, contact the seller and let them know.

I've just had a quick look and these aren't cheap lenses, so unless you got a particularly good bargain, I'd suggest returning it, getting your money back and waiting for another to be advertised.

That'd be my thoughts anyway. There may be someone else who knows how they're put together and whether it an easily fixable problem, but I wouldn't have thought it would be, given the complexity of lenses.

Cheers

Liam

It sounds like lubricant has got onto the diphragm leaves, making them sluggish. Any competent repair house should be able to clean the diaphragm - why not check out the price by calling them?

Yes I bought it on-line and it certainly isn't as described (and it was no bargain either). The seller hasn't had a chance to respond yet and I will wait to see what he has to say before I discuss any specifics of the sale here. Yes, it is returnable but I hate to lose a whole lot of money on shipping and insurance both ways when maybe there is a reasonable fix available. There does not appear to be any oil at all on the actual leaves and the spring seems strong on the lever so I am thinking gummy linkage. Your thoughts?

Drew

I'm no expert on the internal construction of lenses, but I know there need be no real signs of oil or grease to gum up the blades. They are very thin and light and the slightest contamination will be detrimental.

Is the rest of the lens OK? If, for example, it was superb cosmetically and the only defect the one you mention, then a repair might well be a good option.

Otherwise, there are plenty more of them available.

Yes, it is quite good and I like what I see otherwise. John, if you say there doesn't have to be visble signs of grease and you aren't going to recommend a good dunk in some secret fluid then I will check out what it costs for a repair and negotiate from there.

Thanks

Drew

I've had a couple of lenses with sticky blades fixed (the M35/2 and the M85/2) by Camera Repair Direct (which was local to me) - cost me about £35 for a full lens service and they have been fine ever since. I'm not sure if they are still in business though - their website seems to have vanshed. However I guess this gives a good idea of the likely cost of service.

Tony, do you mean these:
http://www.camerarepairdirect.co.uk/
Matt

Yes - but the postal address is wrong - last I was there they had moved to smaller premises (just up the road) and I got the impression trade was not so good. Things are becoming less and less repairable these days.

Try http://www.harrowtechnical.co.uk/ for a quote.