Ricoh GR1v, 28mm

Tokina makes their lenses with a variety of mounts. A lens with Canon mount, for example, won't fit onto a Nikon. Assuming you get the lens with a Nikon mount, then yes, you can use it with a D70 and with a D700.

The FD lenses were mainly for film cameras. I used this lens on a Canon AE1-P. If you have a modern digital EOS with an EF mount you can buy an adapter (FD to EF) so the FD lens can be used on the EOS

If you have Ricoh lenses that do not have electrical contacts, you can use the lenses on Pentax digital SLR cameras.
If you have Ricoh lenses with electrical contacts, you can not use them on Pentax digital cameras.

For what you can buy them for these days, they're excellent and were usually made by Kiron who made excellent lenses in their own name and also for Tokina and Vivitar.

But unless you're using a full frame Nikon (i.e. 35mm or the full frame digital professional bodies) then it's nothing special as it has the same angle of view as a 31.5mm lens (close enough to a 28mm for discussion purposes). A 28mm f3.8 offers no advantage over many of the kit zoom lenses which come with many Nikons and with the huge advances in optical design since the 21mm Vivitar was made are likely to be optically superior.

On balance, if your Nikon is a 35mm film SLR or a full frame sensor version then go for it as it's a fantastic super-wide angle lens. With anything else, it simply doesn't make much sense. What it will still do though is offer fantastic depth of field which will be lacking in relative terms on a 28mm lens designed for APS-C sensors.

Ricoh used the Pentax K-mount.

Pentax are one of only two manufacturers whose current SLR's will accept the older lenses but there will be significant compromises:-

Not all K mounts will work; there's no definitive list so it's "**** it and see".

Most KA mounts should work (KA are the autofocus versions).

All lenses designed for 35mm film SLR's will behave as if they have an approximately 1.5x teleconverter fitted: a 50mm standard lens becomes a 75mm portrait lens, a 28mm wide angle becomes a 42mm and almost indistinguishable from the 50mm standard lens. A typical 80-200mm zoom becomes a 120-300mm zoom and your 600mm becomes a rather less useful 900mm although the effective aperture remains the same.

There will be little if any communication between the lens and the body: K mounts use a mechanical coupling to transmit aperture settings to the body, and the body stops the lens down during exposure with another mechanical coupling. This will no longer work. Some KA lenses will exchange information and automatically stop down. If your current 600mm is a catadioptric (mirror) lens then this is not an issue as it will only have a fixed f8 aperture.

Your current lenses will be to a far inferior optical specification compared to modern lenses. Genuine Ricoh/Rikenon lenses were generally no match for regular Pentax models of the time, and they in turn are generally nowhere near as good as modern lenses. This is because the old models not only use inferior materials technology, but also because modern optics are computer designed and modelled and are optimised for the particular requirements of a digital imager. However, you will generally find that the actual build quality of your old lenses will be superior to modern offerings and they'll be more robust. Also, unless you regularly make large prints or selective enlargements AND regularly use a tripod you may not see the difference in optical quality in real life amateur use. You definitely won't see the difference if you only ever display the photos on a monitor.

Personally, I cannot recommend Pentax dSLR's over any other brand on the basis of legacy use alone, and if the 600mm is the one good lens then I'd seriously consider selling it as there is a demand for good 35mm lenses. I'd give the same advice whichever brand of 35mm you previously used, unless you had a lot of high-end Canon AF/Nikon lenses and were going to buy an expensive full-frame digital SLR. Look at all of the competing offerings and choose what currently suits your photographic needs.

Hope this has helped to clarify things for you, all I ask in return is that you take a brief moment to rate my answer.

how did it went into the D300 in the first place? Hold the metal part of the lens, press the lens release on teh D300 body. Best to send it to Nikon for a look. They would charge shipping only.

This can also happen when the lens have an aperture adjustment ring, and it is not set to the "Auto" setting ("A", on my Sigma)/

Did you put the lens on up-side down? Don't laugh, it happens. If so, hold the lens lock button in (on camera body)and give the lens a quick counter clock wise twist. It should snap out.
If on correctly, turn lens clock wise while pushing in lock button,then with button still pushed in turn the lens counter clock-wise.

I bought a 4 lens kit - I think from Amazon. It was a long time ago.
The size is 28mm.
yes, here it is
http://www.amazon.com/Nikon-28mm-Filter-Set-Coolpix/dp/B0000521B9

You have a one year warranty with Canon, you should have all the information about shipping it to them in your original box.