[blende8]

We all know about the encoding on the A lenses.
It is given here:
Features and Operation of the Ka Mount

But ...
what about the FA and DA lenses?
They all have the same pins, basically.
Not all exactly, but roughly and they do not conform to the pattern given in the above link.

Do we have any info how this works with newer lenses?
I have measured some of my lenses and all pins seem to be non-conductive to the bajonett metal, even if depressed.

And why do DA* lenses have one pin more?

[Ole]

F and later lenses have one pin extra. It is used for digital communication of focal length, lens name, optimal MTF f/stop, and possibly more data. The remaining pins (those common with A lenses) are encoded just like on A lenses. If otherwise the lens wouldn't work on, say, a Super A camera.

Note that a pin which is to be always shorted may not be present since the K-mount metal will take care of the shortening.

[blende8]

Well, this is just too easy.
Look at your FA and DA lenses and tell me how and why they work on an A-type body.

[glasbak]

We all know about the encoding on the A lenses.
It is given here:
Features and Operation of the Ka Mount

But ...
what about the FA and DA lenses?
They all have the same pins, basically.
Not all exactly, but roughly and they do not conform to the pattern given in the above link.

Do we have any info how this works with newer lenses?
I have measured some of my lenses and all pins seem to be non-conductive to the bajonett metal, even if depressed.

And why do DA* lenses have one pin more?

Yeah, I know that page all too well...

The F and FA decoding is still on my todo list.

I do not own any DA* lens, what is different there ?

[Ole]

Well, this is just too easy.
Look at your FA and DA lenses and tell me how and why they work on an A-type body.

They work becasue they have the pins required to signal the min. aperture, the aperture range and the position of the aperture ring. DA lenses of course lack the aperture ring and are coded to always appear to be in "A" mode.

So DA lenses can only work in P and Tv mode on, say, a Super A. Most DA lenses wil vignette and are useless, but some can be used just fine, like the DA 40mm.

What differences have you found that makes you think that the F/FA lenses are not backwards compatible?

[blende8]

Ole, the point is that all DA and almost all FA lenses have the same number and arrangement of pins. They do not conform to Bojidar's list. Nevertheless they work correctly on an A-series camera.

I do not own any DA* lens, what is different there ?

DA* lenses have one more pin:

[glasbak]

Ah, I see.

The F lenses I have here within arm reach still decode the minimum aperture the A lens way.

A quick measurement on the same programA I used years ago reveals :

Camera pins have 2,5 V level when depressing the shutter button,
The A mode contact current is 0.4 mA
All other five draw 0.008 mA

Pure guessing (no time for measurement now), F lenses could code the aperture range by using a zener to lift the voltage for a pin above the A series camera 'shorted contact' detect voltage.

Measuring my SFXn:
All contacts (except the A) about 5V when depressing the shutter button. This is when using 4 nimh cells so supply is about 5V.
The A contact is probed all the time the camera is switched on with a 3ms, 5V pulse every 30ms.

The A series contacts draw 0.12mA.
The extra F contact draws 1.1mA

Pure speculation, but the extra F contact could be the supply for the on lens circuitry.
All digitalcommunication could then go over (one of?) the A contacts.

But further experiments must wait, I have some dutch 5-dec social duties to do

[Ole]

Ole, the point is that all DA and almost all FA lenses have the same number and arrangement of pins. They do not conform to Bojidar's list. Nevertheless they work correctly on an A-series camera.


DA* lenses have one more pin:

I see what you mean.

However, not all A pins need to be present.

The camera's lens mount shows the max number of pins, namely 7. Six A pins and one 7th pin which was introduced with the F lenses.

The DA* lenses can have up to 7 pins in some configuration like all lenses since the F series.

I'm away from home, unfortunately, so I don't have access to much equipment.

Here is what I brought with me - looking at the lens from behind and numbering the pins 1 to 7 counter clock wise:

DA 10-17/3.5-4.5: Pins present: 1 2 3 5 7
FA 24-90/3.4-4.5: Pins present: 1 2 3 5 7, and a cutout at position 4
FA* 80-200/2.8: Pins present: 1 2 3 5 7, and an insulator at position 4
FA* 400/5.6: Pins present: 1 2 3 5 7, and an insulator at position 6

The plot thinckens, you may be on to something, Blende 8.

Perhaps the pins on F and newer lenses are used for more than just the two states present/not present? Otherwise there would be no need for anything beyond insulators/cut-outs, and the A on/off pin.

[Ole]

Taking a closer look at the FA 24-90/3.5-4.5 min f/22-32

Here is what to expect for a f/4.5 to 32 lens from Bojidars table (counterclockwise)

1: data pin - 2: insulator - 3: insulator - 4: insulator - 5: A-pin - 6: short - 7: short

Here is what the lens has:

1: data pin - 2: pin - 3: pin - 4: hole (=insulator) - 5: A-pin - 6: short - 7: pin


So the insulators at positions 2 and 3 were replaced with pins, and the short at position 7 was also replaced with a pin.

Pins cost money, holes do not. So there must be a reason for using pins. Pins were used for the positions signaling the f/stop range (2, 3, and 7) not for the positions signaling the min. f-stop (positions 4 and 6).

On the DA* lens you show, position 4 has also become a pin, where a cut-out or a short would have done the trick had the lens been an A lens.

[glasbak]

Taking a closer look at the FA 24-90/3.5-4.5 min f/22-32


1: data pin - 2: insulator - 3: insulator - 4: insulator - 5: A-pin - 6: short - 7: short

Here is what the lens has:

1: data pin - 2: pin - 3: pin - 4: hole (=insulator) - 5: A-pin - 6: short - 7: pin

Its too early to declare the extra F lenses pin as datapin.
As I suggested above, its probably the supply, and the former maximum aperture range A pins can then be the datapins,
your pin '4' and '6' still decode the minimum aperture as on A series lenses.

[Ole]

Its too early to declare the extra F lenses pin as datapin.
As I suggested above, its probably the supply, and the former maximum aperture range A pins can then be the datapins,
your pin '4' and '6' still decode the minimum aperture as on A series lenses.

I agree, the jury is still out on the "F" pin, although other sources have called it a data pin for the past 20 (?) years! Lets call it the F-pin, then!

[glasbak]

I agree, the jury is still out on the "F" pin, although other sources have called it a data pin for the past 20 (?) years! Lets call it the F-pin, then!

Maybe it was me who named it that way .
When I decoded the A contacts more than 10 years ago, I did not have any autofocus stuff.