pentax zoom

kkennedy

I have a Pentax zoom lens (20+ yrs.) from an old slr. If I purchase a digital slr will the lens still work?

Loves2Watch

If it is that old, the lens mount is different.

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OSV

more than likely, yes... pentax has just about the best backwards compatibility there is... the original k-mount lenses will still fit the brand new pentax dslrs.

if it's an old m42 mount lens, you can still get a factory pentax adapter that will bolt right up to your k20d or whatever pentax dslr you have... here is what the m42 mount looks like:

http://en.wikipedia.org/wiki/M42_lens_mount

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BrianO

Check with Pentax to see if your lens is compatible. They claim their DSLRs work with older Pentax lenses, but they don't say "all". I believe their DSLRs use the Pentax K-mount, but I could be wrong on that score. But if your lens has the old Pentax screw-mount, it is definitely incompatible.

What Loves2Watch says is true for most DSLRs. For example, The Sony Alpha line can use any lens ever made for the Minolta Maxxum but cannot use the older MC and MD series Rokkor-X and Minolta lenses because Minolta changed the lens mount when they introduced the Maxxum in the fall of 1984.

However, Let's assume that your lens is compatible. Then there is something that you need to be aware of. It's known as the 35mm equivalence factor. For the Pentax DSLRs it is 1.5. That means that if your zoom lens has a focal length range of say 80mm to 200 mm then your lens, when attached to the DSLR, will act like a 120 mm to 300 mm lens would on a 35mm SLR. A 50mm "normal" lens would act like a 75 mm lens (short telephoto) would on a 35mm SLR. So, if you are into wide-angle lens photography, you might need to buy a new wide angle lens or wide andle zoom.

The reason for this is that a standard 35mm SLR capatures an image that is 36 mm wide and 24 mm high (to nearest mm) in landscape mode. Most DSLR models use a sensor which is 24mm wide and 16mm high (to nearest mm) so they capture a smaller portion of the image that the lens captures than a 35mm camera would. It's as if the lens has zoomed in by a factor of 1.5 from its actual setting. This smaller size is known as the APS-C size.

While most camera manufacturers use the true APS-C sensor size in their DSLRs, there are exceptions. The equivalence factors used by the major players in their various models are:

Nikon: 1.5 and 1.0
Canon: 1.6, 1.3 and 1.0
Sony: 1.5 and 1.0
Pentax: 1.5
Olympus: 2.0
Minolta: No longer in the camera business*

The cameras with a factor of 1.0 are high-end professional cameras with high-end prices to match: about $3,000 for the camera body alone.


* Konica-Minolta sold their camera/lens division to Sony in early 2006, so the Sony Alpha line is actually a continuation of the now-discontinued Minolta Maxxum line.

OSV

as i stated in my previous post, pentax sells a factory adapter for mounting m42 lenses onto the k-mount body... every pentax lens that's ever been made will bolt right up to the new pentax bodies:
PENTAX K-Bayonet (external) Mount / PENTAX 42mm (universal) Screw-thread (internal) mount
Permits use of PENTAX “S” screwmount lenses on PENTAX K-Bayonet camera bodies.
Manual lens operation only
Aperture-Priority maintained
http://www.pentaxwebstore.com/detail/PTX+30120

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BrianO

Thanks for the explanation on the screw-mount adapter. So his lens should fit the camera regardless of the lens' vintage. We non-Pentax owners learn something new every day.

Loves2Watch

The lens may work with the adapter but auto focus and auto iris and the such will not. So will it work? That remains to be seen.

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OSV

we don't know exactly what zoom lens the o.p. has, but if it's a pentax lens that came with autofocus and autoexposure, all of that will still work with the newer k10d and k20d, the flagship pentax models.

that's because those newer cameras still have the old slot-drive autofocus motor in the body of the camera, and the k-mount electrical contacts all still line up the same... hence the xlnt pentax reputation for supporting every lens that it's ever made, no other camera manufacturer can say the same... although nikon comes pretty close.

if the o.p. has an m42 screw-mount lens, i believe that it probably never came with autofocus and autoexposure to begin with... interestingly, there are m42 adapters that you can get for the latest canon mounts, so the old glass works there as well.

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Loves2Watch

We can banter all day long about this. I seriously doubt it will work given that it is 20+ years old since I have been working with Honeywell/Asahi Pentax exclusively for 40+ years.

To the OP. Plan on it not working and if by some chance it does that's an extra bonus

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OSV

i have a k10d and a number of old lenses that work fine with it, so i speak from first-hand experience.

all that you have done in this thread is spread fud about pentax, without providing the slightest bit of proof as to why any old pentax lens won't work with the newer pentax cameras.

fud is not bantering, it's a waste of bandwidth... the fact that you didn't know about the pentax factory m42 adapter shows how little you know about pentax.

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kkennedy

thank you all for your help