Author Topic: COSINA Self-Contained AF (SCAF) 75-200mm F/4.5 ***** (Read 2890 times)

adash · « **on:** June 19, 2010, 01:08:36 AM »

This is one of the Self-Contained Auto Focus (SCAF) lenses made before AF logic and sensors went to their proper place inside camera bodies. Made somewhere in the eighties (I guess!) for Nikon AI mount. F/4.5 constant aperture, but focus is not constant, i.e. you have to refocus if you wish to zoom in on your subject while shooting. Has three AAA batteries and four modes of operation: Single AF, Continuous AF, MF and PowerZoom. Since DOF is quite small at these lengths, your adapter must be super-dooper accurate. I asked a fellow machinist to do an adjustable adapter and he agreed. I adjusted it with cardboard after several attempts.
Advantage are:
- AF;
- Faster apertures than Digital Zuiko 40-150 and Pany 45-200;
- Constant aperture.
Disadvantages follow:
- It is heavy;
- It is slow;
- You never know where exactly it focused;
- It simply refuses to AF in dim light;
- It misfocuses quite often;
- It's not very sharp;
- It is not convenient for MF, since you can only rotate a small ring at the very front;
- Front element is rotating.

Here come the lens sample pictures:

75mm:

F/4.5:

100% crop:

F/5.6:

F/8:

F/11:

100mm:

F/4.5:

F/5.6:

F/8:

F/11:

135mm:

F/4.5

F/5.6:

F/8:

F/11:

200mm:

F/4.5:

F/5.6:

F/8:

F/11:

adash · « **Reply #1 on:** June 19, 2010, 02:05:40 AM »

The lens itself, together with the custom adapter:

Details

cosinaphile · « **Reply #2 on:** January 19, 2011, 11:41:34 AM »

i have two vivitar branded lenses in om mount that operate on a similar principle 3 triple a`s
AAA batteries a 28-70 3.5 -4.5 and a 75-200 as well

adash · « **Reply #3 on:** January 19, 2011, 12:07:41 PM »

I think the 75-200 is the same, except for the power zoom.

Em5 Pete · « **Reply #4 on:** January 19, 2011, 08:59:02 PM »

I remember Canon made a 35-70 AF zoom in the FD mount (T series cameras at the time), a few others made some also, but within a few years, Canon introduced the EOS mount... way ahead of it's time... with no mechanical links from the lens to the body.

adash · « **Reply #5 on:** January 19, 2011, 11:08:32 PM »

The FD lens (as far as I know) used a sort of focusing like an RF (I have only seen pictures of it) with two small windows on the front panel. The Vivitar/Cosina SCAFs however use a beam-splitting prism (sort of a translucent mirror) for supplying light to both the camera and the AF sensors within the lens itself.

Em5 Pete · « **Reply #6 on:** January 20, 2011, 07:29:23 AM »

Quote from: adash on January 19, 2011, 11:08:32 PM

The FD lens (as far as I know) used a sort of focusing like an RF (I have only seen pictures of it) with two small windows on the front panel. The Vivitar/Cosina SCAFs however use a beam-splitting prism (sort of a translucent mirror) for supplying light to both the camera and the AF sensors within the lens itself.

Yes, that's right, it has 2 red area's that used Infer-Red maybe? . It was slow, and not too accurate either.

adash · « **Reply #7 on:** January 20, 2011, 08:51:06 AM »

The Cosina SCAF above is slow and not too accurate too. I guess that's what the technology of the time allowed.

Em5 Pete · « **Reply #8 on:** January 20, 2011, 10:48:32 AM »

I think when Canon figured how to use a slit/mirror with an AF sensor in the base of the camera, that was a break through. Maybe these few On-Lens AF motors where to "test" technologies for "In-Body" sensors??

adash · « **Reply #9 on:** January 20, 2011, 12:17:14 PM »

Yheah, that might have been a convenient way to test the technology without exclusively build new camera bodies/AF lens mounts etc.

Em5 Pete · « **Reply #10 on:** January 20, 2011, 07:00:43 PM »

Quote from: adash on January 20, 2011, 12:17:14 PM

Yheah, that might have been a convenient way to test the technology without exclusively build new camera bodies/AF lens mounts etc.

The T90 had a lot of EOS technology inside.
And a tank of a camera... Just a tad small in my eyes at the time.

adash · « **Reply #11 on:** January 20, 2011, 11:48:14 PM »

Indeed, but I think this self-contained AF lens by Canon was also available for users of much older cameras with the FD mount.
Also offerings from COSINA/VIVITAR were available in virtually any lens mount at that time, much increasing user base. Unfortunately the technology was neither mature nor convenient enough for it to catch up or compete with genuine AF bodies.

COSINA Self-Contained AF (SCAF) 75-200mm F/4.5 *****