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12-30-2012, 04:08 PM   #1
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teleconverter modification electrical contacts help needed

In order to have shake reduction work correctly, I want to tape the electrical contacts on one or more of my TCs so that I have to manually enter the focal length of the lens rather than having the TC passively transmit the focal length of the attached lens. I want all other functions to be unchanged. Which contact or contacts do I tape over?

My specifics are a K-5 and a Sigma 500mm f/4.5 lens coupled with the Sigma 1.4, or Sigma 2.0, or Tamron 1.4 teleconverter. I want the camera to think that this combination is a 750mm lens rather than what it now thinks, which is that it is dealing with a 500mm lens. If there is a way to accomplish this through a software hack that would be great, but any solution would be welcomed.

Russ

12-30-2012, 04:23 PM   #2
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I would try covering the one closest to the center, beside the screw, that is the data pin. You are going to disable auto focus though, it will think the lens is just a standard manual focus A lens.
12-30-2012, 04:52 PM   #3
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Not sure if Pentax knows of a 750mm length lens... I don't use SR much but from what I remember there were only a certain number of values you could set it to and is 750mm one of them?
12-30-2012, 05:10 PM   #4
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QuoteOriginally posted by Nass Quote
Not sure if Pentax knows of a 750mm length lens... I don't use SR much but from what I remember there were only a certain number of values you could set it to and is 750mm one of them?
There is 700 and 800, 700 is close enough, I'd keep it too short rather than too long.

12-30-2012, 05:38 PM   #5
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2 points

I always thought the camera worked it out when a converter is used.

But you got me thinking. I have taken the lenses out of a cheap teleconverter to make an extension tube. If I am right, the camera will be correcting camera shake for a teleconverter.
12-30-2012, 06:03 PM   #6
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If it is correcting it automatically you'll see it in the EXIF under focal length. It would be up to the teleconverter to do the correction, it would have to read the focal length from the lens, multiply that by the magnification of the teleconverter, then send that to the camera. I don't have any auto focus teleconverters, so I have no idea if they do this or not.
12-31-2012, 07:34 AM   #7
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QuoteOriginally posted by oeriies Quote
In order to have shake reduction work correctly, I want to tape the electrical contacts on one or more of my TCs so that I have to manually enter the focal length of the lens rather than having the TC passively transmit the focal length of the attached lens. I want all other functions to be unchanged. Which contact or contacts do I tape over?

My specifics are a K-5 and a Sigma 500mm f/4.5 lens coupled with the Sigma 1.4, or Sigma 2.0, or Tamron 1.4 teleconverter. I want the camera to think that this combination is a 750mm lens rather than what it now thinks, which is that it is dealing with a 500mm lens. If there is a way to accomplish this through a software hack that would be great, but any solution would be welcomed.

Russ
Thanks to everyone for the replies. I followed up and here is what I found: a) Based on the EXIF data every teleconverter I own except the Pentax-F 1.7 passes the lens information from the attached lens to the camera unmodified. Thus for the two Sigma TCs and the Tamron (and I expect for every other TC out there except the 1.7) a lens of a particular focal length, e.g., 500mm, is seen by the camera as a 500mm lens regardless of the attached TC. b) Taping over the data contact pin allows manual setting of the lens focal length but autofocus is lost. c) Attaching the TC to the camera before a lens is attached and turning the camera on allows manual setting of the focal length, but when the lens is attached the camera defaults back to the actual lens focal length, e.g., the manual setting of 700mm defaults back to 500mm for a 500mm lens.

This means that for a modern lens with a TC attached in-camera shake reduction on a Pentax body will always be working with the wrong input value for lens length unless the data contact pin is taped over, in which case the lens becomes a manual lens, or the TC is the Pentax 1.7, which in effect also turns a modern lens into a manual lens.

This is something Pentax could and should fix through software by allowing an option of manual override of the lens length value on a lens-by-lens, just as it currently allows a microfocus adjustment on a lens-by-lens basis. Thus for my 500mm lens, which is the only one to which I attach at TC, I could set a custom function that always requires me to set a manual focal length when I attach that lens. Alternatively, if Pentax every gets around to making a modern TC it could build electronics into it that transmit the correct lens length.

I don't know how much of problem the wrong lens length value creates for shake reduction. I never turn shake reduction off and manage to get acceptably sharp images using a 1.4 TC, but I'm always shooting from a tripod when I'm using a TC so maybe there's no shake for the shake reduction system to reduce.

Russ

12-31-2012, 07:43 AM   #8
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If Pentax's own teleconverter modifies the focal length, it would seem they don't have anything to fix, Sigma and Tamron should fix their teleconverters. It makes no sense for Pentax to add workarounds for third party products, no one else does.

Also, shake reduction should be turned off when you are on a tripod. With the K-5 you can use the 2s delay and it will be off.
12-31-2012, 07:43 AM   #9
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There have been requests to Pentax specifically since the introduction of shake reduction to add a tele converter prompt, lust like focal length, to modify the focal length reporting for SR and also to modify the aperture, such that P-TTL can work correctly. Pentax has responded that they are not responsible to make third party accessories function
12-31-2012, 10:19 AM   #10
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QuoteOriginally posted by elliott Quote
If Pentax's own teleconverter modifies the focal length, it would seem they don't have anything to fix, Sigma and Tamron should fix their teleconverters. It makes no sense for Pentax to add workarounds for third party products, no one else does.

Also, shake reduction should be turned off when you are on a tripod. With the K-5 you can use the 2s delay and it will be off.
The F 1.7 isn't really modifying the focal length in the sense of knowing what it is attached to. Rather it is recognized by the camera as an A series lens and the aperture and autofocus functions work entirely within the 1.7. But you're right that there's nothing Pentax has to fix about the 1.7. I would agree that Pentax shouldn't have to engineer workarounds for other manufacturers add-ons IF Pentax made their own. But Pentax doesn't make a current TC and it holds a niche of the overall market for DSLRs, so low cost efforts to expand the system that is available to Pentax users by working with manufacturers of add-on lens products would be a good idea, IMHO.

QuoteOriginally posted by elliott Quote
.

Also, shake reduction should be turned off when you are on a tripod. With the K-5 you can use the 2s delay and it will be off.
Thanks for the recommendation to turn off shake reduction on a tripod. That is the advice given in the K-5 manual and I understand the technical argument for it (the sensor movement itself can introduce blur and the axis of rotation assumed by the camera is wrong). But doing so doesn't work for me: I shoot birds and wildlife with my long lens so waiting two seconds typically means the subject has moved on. If I turn off shake reduction entirely the chance that I'll forget to turn it back on is high. And if I've turned off SR and I'm on a monopod and need a quick hand held shot where SR is really important I don't have it.

There's also for me a question of whether the residual shake that occurs without fail on a monopod and to some degree even on a tripod when shooting with no delay is helped by SR. Ken Rockwell seems to think so. He says, "I usually turn off VR on a [very sturdy] tripod; it's not needed. If I leave it on, I've never seen a problem either...but if you're in the wind or the tripod is otherwise unstable, VR and IS will help. ... I use it on monopods, too."

It would be great to see some actual test data on SR in various conditions of use, with and without TCs. I would be particular interested to see some evidence on whether it does any harm when it is turned on but not needed, and whether it helps with the small movements that occur as a result of wind or shutter activation even when shooting from a tripod.
12-31-2012, 12:41 PM   #11
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Set up user profiles. Name them appropriately. Some with Sr some not. Get into a habit of shutting the camera off when you change mounts.

Every manufacturer does Sr differently. Some might be affected by tripod, others not. The panning motion or even the one axis swing on a monopod does nasty things to the Pentax Sr in some circumstances.
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