Nikon D750 manual lens problem?

I have a new old stock Nikon D750 acquired this year. It hasn't been used much but I had a day out yesterday in the mountains using an Irix 15mm f2.4 and a couple of other manual focus lenses plus a new 50mm f1.4.

Everything worked fine but today, the Irix refuses to work properly in anything but M mode (it should work fine, albeit with manual focus, in M A S and P modes but suddenly it can't read the aperture in any of those modes, and only allows the shutter to fire in M. It does the same with other non-autofocus lenses as well but is 100% fine with a normal autofocus lens....

Is there anything I might have inadvertantly reset or changed that could be causing this, or does it sound like a comms failure between camera and lens...?

You can try cleaning the contacts on camera and lens (I think the Irix lens is manual focus with electronic contacts).

If you have other manual focus lenses that don't have a CPU or electronic contacts, like a Nikon AI non-AF lens, those should work with the camera but only in M or A modes, not S or P. Read the section of the manual on "non-CPU lenses" to find out more.

reddesert said:

You can try cleaning the contacts on camera and lens (I think the Irix lens is manual focus with electronic contacts).

If you have other manual focus lenses that don't have a CPU or electronic contacts, like a Nikon AI non-AF lens, those should work with the camera but only in M or A modes, not S or P. Read the section of the manual on "non-CPU lenses" to find out more.

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Thanks for taking the time to reply. I managed to sort the problem but I'm not overly impressed with Irix quality control - as I half suspected, it turned out to be a comms problem in that, on close inspections of the lens contacts, one of them was slightly depressed and obviously not making proper contact. A quick flick with a fingernail and it popped up again and everything works as it should.

But for a brand new lens that's been used 3/4 times it's not good news.

Cleaning dirt off the contacts seems to have corrected your problem. When there are problems check the battery strength.

Sirius Glass said:

Cleaning dirt off the contacts seems to have corrected your problem. When there are problems check the battery strength.

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No it wasn't dirt, its a brand new lens. One contact was stuck in a slightly depressed state, barely visible or I'd have spotted it sooner. Just annoying on a new lens.

I've noticed quite a few for sale second hand too - more than one would expect which makes me wonder.

Thwyllo said:

No it wasn't dirt, its a brand new lens. One contact was stuck in a slightly depressed state, barely visible or I'd have spotted it sooner. Just annoying on a new lens.

I've noticed quite a few for sale second hand too - more than one would expect which makes me wonder.

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I understand now. One would expect better quality control with new equipment. I hope it gives you better service in the future.

Sirius Glass said:

I understand now. One would expect better quality control with new equipment. I hope it gives you better service in the future.

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Well I have to say that performance-wise it's outstanding, if a little on the large side despite being manual focus. But the price is spectacularly lower than a lot of its competition and Irix isn't exactly a mainstream manufacturer so who knows?