A new lens

[pschlute]

Well , new for me, but it was manufactured over 41 years ago. One of the nice things about being part of the minority interest that is Pentax is being able to use any K-mount lens that has ever been manufactured.

This one is a beauty and looks like it just came out of the box in 1975!

I do collect old lenses but it is nice to be able to give them an occasional outing, especially as I now use the Pentax Full Frame k-1, so they can once again be used (sort of) in the way they were designed to be.

[Shadowman]

Nice looking lens.

[xpatUSA]

Well , new for me, but it was manufactured over 41 years ago. One of the nice things about being part of the minority interest that is Pentax is being able to use any K-mount lens that has ever been manufactured.

This one is a beauty and looks like it just came out of the box in 1975!

I do collect old lenses but it is nice to be able to give them an occasional outing, especially as I now use the Pentax Full Frame k-1, so they can once again be used (sort of) in the way they were designed to be.

I recently bought two M42 Asahi Co Takumar lenses, one Super 28mm the other SMC 24mm - both mint with hoods, caps and only slightly worn leather cases.

Using them on a Sigma SD14 with M42-SA adapters, very nice indeed. A lot of lens for $50-100 on U.S. eBay, I reckon.

[rpcrowe]

I had a Vivitar 90mm f/2.5 (not the f/2.8 model) Series One Macro lens with a Pentax bayonet mount used on a Pentax MX camera that was about the sharpest lens that I have ever used. One drawback is that the shooting ratio was only 1:2; needing an adapter making it into a 1:1 ratio macro.

That need for the adapter was a big PITA when shooting around the 1:2 through 1:1 ratio.

[pschlute]

I had a Vivitar 90mm f/2.5i.......used on a Pentax MX camera

Pentax MX was my first camera in 1978. I used it for 13 years. It has had one service in the intervening years and still gets an occasional trip out in the camera bag. Taking pictures with film really makes you slow down and think.

[rpcrowe]

I had both the ME and MX - really nice pair of cameras...

[GrahamS]

That is one superb lens, you are very lucky to find one in such good nick. Enjoy!

[Manfred M]

I will be interested in hearing how well this lens works on a modern digital body.

I have read that some of the old film lenses are not particularly strong performers on digital bodies because the designers did not (in fact could not) account for the thickness of the optical stack in front of the sensor versus the very thin emulsion on a film.

https://wordpress.lensrentals.com/bl...dapted-lenses/

[xpatUSA]

I will be interested in hearing how well this lens works on a modern digital body.

I have read that some of the old film lenses are not particularly strong performers on digital bodies because the designers did not (in fact could not) account for the thickness of the optical stack in front of the sensor versus the very thin emulsion on a film.

https://wordpress.lensrentals.com/bl...dapted-lenses/

Interesting link to me because my 40-yr old Takumars work very well on my Sigma DSLRs, perhaps because they have no stacks on their sensors at all, apart from micro lenses.

[GrahamS]

Nothing to do with the "stack" but to do with the angle of incidence of the light rays projected from the rear of the lens to the sensor surface and also the reflection from the sensor surface back into the lens.

[pschlute]

The coatings on these old lenses which were very good in their day and perfect for film, are generally not up to scratch on a digital sensor which is more susceptible to flare caused by stray light. This can lead to images lacking contrast.

Choosing your scene correctly to avoid glare, and using a hood is important.

There are those that say the resolving ability of older lenses is not good enough for a digital sensor, but I think this depends entirely on the sensor and most importantly the size of your end picture/print.

Most of all though , I just enjoy using them for the fun factor, whether on a modern body or on a film camera from the same era.

I will post some pictures when i get the chance.

[Manfred M]

Interesting link to me because my 40-yr old Takumars work very well on my Sigma DSLRs, perhaps because they have no stacks on their sensors at all, apart from micro lenses.

There is a follow-up article that discusses the subject a bit further here:

https://www.lensrentals.com/blog/201...oes-it-matter/

It makes a lot of sense to me. When an additional optical element is introduced, the way that the light converges at the film / sensor plane will be affected as different wavelengths of light travel through glass at different speeds. The old lenses were designed to ensure that the rays converge at the film plane.

Add the optical stack and all of a sudden this does not happen any more and the different wavelengths of light will no longer converge where they were designed to, i.e. at the microlens position. This is going to be especially apparent in fast, wide angle lenses more so than longer, slower lenses.

I'm a little surprised that the Sigma does not have some level of protection in front of the microlenses. There is obviously no need for an AA filter and I guess the IR / UV filter could be integrated into the layers of the sensor. I would have thought that some sort of protective layer over the assembly would have made sense.

[rpcrowe]

I also think that the quality of digital imagery from a lens depends a lot on the original quality of that lens. As an example, I have a Canon EF 50mm Mk.I lens which was one of the first EOS lenses introduced. Obviously, it was introduced for film cameras but, it does an excellent job with a digital camera...

My "new-old" Tokina 28-70mm f/2.8 ATX Pro lens is an old design (this was based on the Angenieux 28-70mm f/2.6) but it does a great job on my full frame Canon cameras as well as on my crop cameras...

[xpatUSA]

There is a follow-up article that discusses the subject a bit further here:

https://www.lensrentals.com/blog/201...oes-it-matter/

Thanks for the link!

It makes a lot of sense to me. When an additional optical element is introduced, the way that the light converges at the film / sensor plane will be affected as different wavelengths of light travel through glass at different speeds. The old lenses were designed to ensure that the rays converge at the film plane.
Add the optical stack and all of a sudden this does not happen any more and the different wavelengths of light will no longer converge where they were designed to, i.e. at the microlens position. This is going to be especially apparent in fast, wide angle lenses more so than longer, slower lenses.

I'm a little surprised that the Sigma does not have some level of protection in front of the microlenses. There is obviously no need for an AA filter and I guess the IR / UV filter could be integrated into the layers of the sensor.

Not really. The three layers responses are broad enough that all three respond to IR radiation well outside of the visible spectrum.

I would have thought that some sort of protective layer over the assembly would have made sense.

In the Sigma DSLRs, the sensor is protected by a combined dust-cover/UVIR dichroic 'hot-mirror' mounted just behind the lens mount. As to additional glass on the sensor itself, I don't know for sure - the patent copies don't show any but looking into the camera it's unlikely to be over about 1/2mm deep.

[Manfred M]

As to addition glass on the sensor, I don't know for sure, the patent copies don't show any.

My understanding is that the "stack" is not neccessarily part of the sensor per se and in most cases is held in place by mechanical means, i.e. these elements can be removed, for instance to remove the IR filter so that the camera can be used for IR photography. This would suggest those elements might not show up as part of the patent.

[xpatUSA]

My understanding is that the "stack" is not neccessarily part of the sensor per se and in most cases is held in place by mechanical means, i.e. these elements can be removed, for instance to remove the IR filter so that the camera can be used for IR photography. This would suggest those elements might not show up as part of the patent.

Yes, that's what I thought too - great minds, etc.

Of course, by "layers" I was not referring to the "stack". I was responding to your thought that "I guess the IR / UV filter could be integrated into the layers of the sensor" and showing with the graph how that could not be.

[Manfred M]

I was responding to your thought that "I guess the IR / UV filter could be integrated into the layers of the sensor" and showing with the graph how that could not be.

I was under the impression that the R, B and B filters were part of the three layers of the Foveon sensor, so had assumed that IR / UV could technically be incorporated into that functionality. Thinking about it a bit more, it wouldn't work.

[pschlute]

I have been very busy and not had time to give this lens a proper outing. Today i had a window and grabbed the lens and camera to try and showcase it's capabilities. I don't I succeeded and this image is not anything special at all, but i think they do show the unique perspective an ultra wide can deliver, and it was fun playing with it. The lens does have significant distortion at the edges which can also be quite soft. However I am impressed with the centre sharpness at least close up.

[rpcrowe]

Very nice, there is almost 3-dimensional feeling in his image.