NEED TC TECH INFO

[thermalguy]

First I'm planning on getting the 300-600 Sigma F4.0 when it starts shipping to attach to a SONY A7RV.

Second I have a background of 25 years in the Night Vision Industry many of which was in development so I understand Optics, Mechanics and Electronics to a technical level.

So now to the question, can I take a Sony 1.4x or 2.0x TC (teleconverter) and modify it so that I will get full lens functionality?

Let me explain my reasoning - when you use the TC the camera knows that the TC is there as it is in the metadata in the photo that it was used. So the TC must have some kind of circuit for this to happen, or at a minimum a contact is being pulled high or low so the camera sees something (the TC) is there.

So if I disassembled the TC and removed any circuits and just make all the contacts and pins a straight pass through then the 300-600mm should have full functionality, at least in theory. Now I will lose the camera knowing that the TC is there and it will not be in the metadata but I'm ok with this.

If this has been talked about before please send the link and if not please give me some feedback of this modified TC concept and if you think it might work.

 

[Impulses]

First I'm planning on getting the 300-600 Sigma F4.0 when it starts shipping to attach to a SONY A7RV.

Second I have a background of 25 years in the Night Vision Industry many of which was in development so I understand Optics, Mechanics and Electronics to a technical level.

So now to the question, can I take a Sony 1.4x or 2.0x TC (teleconverter) and modify it so that I will get full lens functionality?

More than likely, no...

Let me explain my reasoning - when you use the TC the camera knows that the TC is there as it is in the metadata in the photo that it was used. So the TC must have some kind of circuit for this to happen, or at a minimum a contact is being pulled high or low so the camera sees something (the TC) is there.

The TC passes thru full communication from the lens, yes. Would be fun to see the attempt, pricey as it'll be.

So if I disassembled the TC and removed any circuits and just make all the contacts and pins a straight pass through then the 300-600mm should have full functionality, at least in theory. Now I will lose the camera knowing that the TC is there and it will not be in the metadata but I'm ok with this.

Sounds like an alignment nightmare, and a dead TC.

If this has been talked about before please send the link and if not please give me some feedback of this modified TC concept and if you think it might work.

I guess as a first step you could start with extension tubes and the 300-600, some of the connections might be useful for the Franken-TC, then look into how easy (if at all possible) it would be to disassemble the Sony TCs...

Edit: Seems as recently as A mount there were manuals online for TC repair and recycle (straight from Sony even...), but that doesn't seem to be the case for E mount, that I've seen. Could be wrong, lens disassembly in general seems to have gotten more complicated as lenses rely more on electronics, ribbon wires galore.

 

[Heritage Cameras]

So if I disassembled the TC and removed any circuits and just make all the contacts and pins a straight pass through then the 300-600mm should have full functionality, at least in theory. Now I will lose the camera knowing that the TC is there and it will not be in the metadata but I'm ok with this.

Some early tele converters for AF SLRs used this passthrough approach. One problem is that even if it works, the focal length will be reported to the camera wrongly. The IBIS will be trying to correct a 600mm lens when it should be 1200mm...

 

[Heritage Cameras]

So if I disassembled the TC and removed any circuits and just make all the contacts and pins a straight pass through then the 300-600mm should have full functionality, at least in theory. Now I will lose the camera knowing that the TC is there and it will not be in the metadata but I'm ok with this.

Some early tele converters for AF SLRs used this passthrough approach. One problem is that even if it works, the focal length will be reported to the camera wrongly. The IBIS will be trying to correct a 600mm lens when it should be 1200mm...

 

[heiberger]

Based on the service manual it seems theoretically possible. There is a circuit board that would need to be removed and replaced with a connector for the flat flexible cables from each side, turning it into a “dumb” optical-only connector, akin to the aforementioned extension tubes. Whether it’s actually practical to get it apart and back together, aligned, I don’t know.

Reply #4 at Fred Miranda mentions this but it’s not clear if the user actually did it.

If you do this and are successful (or not!) please let us know.

 

[thermalguy]

I really like the idea of testing it with an extension tube, if that works then I would know it will work if I can remove the circuit and just have a pass through.

I do not care about the metadata info saying 600mm when it will be 840mm or 1200mm depending on a 1.4x or 2x TC.

Back in the 1990's we would dismantle Canon tubes to get the front and rear bayonet connectors, we would then attach them to a machined tube that had a Image Intensifier in it and a corrective lens assembly. They would be used by law enforcement for night time surveillance.

 

[QuietOC]

My guess is that the Sigma lenses that don't respond correctly to the camera when they are mounted on the Sony FE teleconverters. You might only need to modify the Sigma lens firmware to respond correctly. The data has to come from the lens.

 

[UncleVanya]

This seems plausible. Typically other designs are similar the camera is informed by the tc that it is there and calculates the focal length and sprite modifications. You could set manual steady shot focal lengths as needed.