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07-12-2010, 06:41 AM   #1
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Trying to set the lens mm for shake reduction

I have a sigma lens and when i put the sigma 1.4T.C. on the camere it doesn't show the change. It see's the lens and reports but not with the T.C.
How do you change this on the k-7. I think if it reports correctly it will give better results. Is that correct?
Thanks

07-12-2010, 06:52 AM   #2
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Yes, you should see better results, as at a longer focal length, more sensor movement is required for effective SR.

You should be able to manually set the SR focal length in the camera record menu, under 'Shake Reduction'.

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07-12-2010, 09:56 AM   #3
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If it's a manual lens, you can set the focal length. If not, you can't - so you do indeed get less-than-ideal results from SR when using a TC, unless the TC transmits the new focal length correctly (and I don't think any of them do).

In addition to the loss of light and the overal degradation in IQ, this is just one more reason why using a TC with a DSLR just doesn't make nearly as much sense as it did in the days before cropping wasn't as trivially easy as it is now. You don't say which Sigma lens you are using. If its a relatively high end one, the tC will indeed probably do better than cropping. but if it's just something like the 18-250 or 70-300, then you're almost *definitely* better off simply cropping.
07-13-2010, 01:59 AM   #4
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You know that is just down right bad stupid. And i am sure they know of this problem. Why do they do such things? It is simply a simple software fix.

I really do not understand the logic behind this.

I have a fast 2.8 telephoto and when i put a 1.4 t.c. on, it does not report. But the lens does and the proper focal length in the camera is locked at the lens that it sees.

07-13-2010, 02:00 AM   #5
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Do any of you know who i can complain to? Or should i go to the pentax offical web site and put in a complant?
Thanks
07-13-2010, 02:11 AM   #6
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IT is a problem of your Sigma teleconverter, not Pentax gear.
Because teleconverter must recalculate focal length.
07-13-2010, 03:21 AM   #7
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It is not a problem with sigma if it is a simple software fix. This is a deliberate thing they have done. It has nothing to do with sigma only with pentax for some reason.
It really does not make sense. I have writen to Pentax and asked them why they do this. I will relay the response.
On there offical web page it says they are not responsible for third party lens and there shake reduction system.
I have a feeling they did this on purpose.
For the life of me i do not know why.
07-13-2010, 03:52 AM   #8
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The problem is with definitely with sigma because it is lens who delivers its information to body. It is AF teleconverter who must modify the data it gets from lens and return modified data to body.
If you knew how data transfer is organized and what data is transfered between body-lens you would understand what I mean.

PS: Pentax would either skip you message or reply that you should use only Pentax lens. Why would they bother to support third party lens? Hehe

PPS: It would be ridiculous if original gear would support third party lens.

07-13-2010, 04:20 AM   #9
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The Pentax system is pretty much foolproof, as you're guaranteed to get the most accurate SR at every focal length with modern lenses. The Sigma TC should either recalculate the FL or simply not transmit any data, so that it could be set manually.

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07-13-2010, 04:51 AM   #10
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Sorry Gary, it is a Sigma problem. If the TC doesn't tell the camera what it's doing, how is the camera supposed to know?
07-13-2010, 05:23 AM   #11
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Gary / All

this problem has been around since the release of the K100D.

The argument I got from pentax on the K10D when I raised this issue of teleconverters was that since pentax do not make any tele converters they see no reason to accomodate for them.

But the problem is much worse than focal length and highly dependant on brand of teleconverter.

Sigma TCs are "dumb" units, they just feed the values from the lens directly, This means that both reported focal length and aperture are incorrect.

Focal length impacts all sorts of functions including the curves for exposure related to shutter speed, flash sync speed in AV mode etc. more importantly any function that is automated and takes focal length into account.

Aperture impacts greatly the metering because the newer focusing screens have a non linear behavior with reflecting back to the metering sensor, which is aperture dependant, and programmed out of the equation. But if you put a sigma TC between lens and camera, the TC changes the aperture and the metering is off. On my K10D (the worst offender with respect to metering) I need to add 0.7 stops when using my Sigma 1.4x TC on my APO 70-200F2.8 and 1.3 stops whe I use the 2x

As I said earlier the problem is every TC is different. My SMC-F 1.7x AF TC corrects for aperture, and since it is meant to convert MF to FF does not feed focal length at all, so you do itr manually, but the Takumar A teleconverter does not correct for aperture so even pentax is not consistent in the approach.


As for cameras, even the K7 does not take teleconverters into account.

I proposed to pentax 4 years ago, that you have a custom menu function or start-up prompt like manual lenses that would allow you to pick the TC multiplication, and options to use this to correct for aperture, focal length both or none. I'm still waiting.

On the bright side, the K7 metering perfromance with manual lenses below F5.6 is much improved over the K10D and as a result, at least much of the exposure issue has gone away

Edit note: As far as the performance of shake reduction and the efficiency when using a TC that does not alter focal length, I can't put a scientific number to it, but my impression is that it costs you about 1 stop in terms of hand holding. For example, on my K10D with the sigma 70-200F2.8 and a 2x TC, I can hand hold to between 1/60 and 1/100, so I get between 2 and 3 stops advantage over 1/focal length. On my K7 with my 300mmF4 and 1.7x TC and manually entering 500mm Focal length, I have shot at 1/40th successfully. I have even posted those results, 1/40th is 3 1/2 stops down from 1/focal length.

Althouogh the SR performance is better with an accurate focal length, good techique and even partial compensation gets you a lot. Although the SR issue buggs e, the exposure issues and other functions are fare more serious.

Last edited by Lowell Goudge; 07-13-2010 at 05:33 AM.
07-13-2010, 09:19 AM   #12
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Not only is the issue with the TC, not the camera, it's also not (just) a software issue. Most likely, the TC lacks any sort of processor to *run* the software that would be needed to convert the focal length.

As it stands, the camera has no idea idea a TC is even being used unless the TC was designed to advertise its presence via the lens contacts, and clearly, this isn't happening. Sigma would have to redesign the TC to include some sort of microprocessor in order to fix this.

Last edited by Marc Sabatella; 07-13-2010 at 12:13 PM.
07-13-2010, 12:11 PM   #13
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QuoteOriginally posted by gary1952 Quote
It is not a problem with sigma if it is a simple software fix. This is a deliberate thing they have done. It has nothing to do with sigma only with pentax for some reason.
It really does not make sense. I have writen to Pentax and asked them why they do this. I will relay the response.
On there offical web page it says they are not responsible for third party lens and there shake reduction system.
I have a feeling they did this on purpose.
For the life of me i do not know why.
So, how is the camera supposed to know what is attached to it if the equipment that is being installed doesn't talk to the camera?
And, why should Pentax be at fault for failing to support non Pentax equipment?
It is the responsibility of third party manufacturers to ensure that their products are in compliance with first party manufacturers equipment.
Stigma has a long and rather ignominious track record in this regard.
That you are on the wrong side of it is hardly the fault of Pentax.
07-14-2010, 04:21 AM   #14
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Lowell very good info.. Thanks alot.
I did not know about the other problems that go along with mm reporting. I am glad i have the k-7 at least. Sounds like shake reduction and not reporting the proper mm is not serious.

Your complaint is exactly what i proposed to Pentax in my complaint to them. I guess i will not get any response. As a programmer in my former life. This seems completly wrong to me. If you can report a non reporting lens and the tc.
Then you can surly report a reporting lens with a dumb tc. Surley it is a function call or object call, that is called when a non reporting lens is attached.
Your idea of a menu that corrects for this is the only way to go i think. But even simpler is just not have the menu selection go dim. Or not being able to use the menu item. This is just wrong!!!!!!

I will continue to complain about this software issue. Untill I have someone that can explain to me why it is not!!

Thanks

Last edited by gary1952; 07-14-2010 at 05:04 AM.
07-14-2010, 04:50 AM   #15
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QuoteOriginally posted by gary1952 Quote
Actually i see where all of you are comming from. And one guy reall enlightened me.

But the fact remains if you have a MF lens you have the option to set the correct mm of the lens and the tc !! But if you have a reporting lens the option goes away. And is not accesible!! That is my gripe. It would be nice if you could set or override this function in the software rather than just completly going away and not having the option to set it manually.

Now if the T.C. makes no difference in the shake reduction process then i see where it is not a problem.

Next Question: Is the main lens that reports the only thing that needs to reoprt to give the camera the proper info for the shake reduction to work properly and now with meetering??? properly ( even with a t.c. connected that is not reporting )?

I have a sigma 300mm f2.8 lens with matching sigma tc's. I was wondering if this is a problem with the shake reduction? The lens reports no problem. Now i guess there is a problem with other functions also. This makes all fast glass completly usless with a t. c.?

I will continue to complain about the software issue.

Thanks Lowell. You make a lot of sence. The only one that has reported this problem and understands i think.
I think you have a very good idea there. It is not a very good idea to isolate other manufactures when you do not make fast glass.
Gary

First of all, your 1.4x TC and sigma 300F2.8 are not useless when it comes to SR, all it means is that you are perhaps limited to 1/100 not 1/40 like I can actually hand hlod with a 500mm lens properly corrected.

The ideal solution would be to allow as I indicated an option to consider the CT in custom menus etc, or to allow for "tuneable" shake reduction in general. This might not be a bad idea any way, let people tune the camera to their needs, but I doubt it will happen. to get the controls down to something most users would understand would be difficult at best. SO you are left with requesting from pentax the user menu option for teleconverter correction



but in the end, I can tell you something, the impact on SR is not serious. Yes it would be nice, and yes, lots of people complained about it, BUT when using a 300+mm lens for wild life, I find that with few examples, hand holding to 1/40 is not practical regardless of whether you can do it or not. The reason is, aside from a few birds like herons, who can actually sit incredibly still, most move around so much that you get motion blurr from their own movement. One thing people forget is that SR only deals with movement at the camera, not the subject. Also when tracking moving objects, SR should be off because the camera can't distinguisg intended movement from unintended, and causes slight blurr of the subjects.

what is more important to me is metering.
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