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07-14-2010, 05:54 AM   #16
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Hey Lowell
Yes i agree. It sounds like meetering is the most important issue. I also shoot birds. And most of the time with a gimble head on the tripod. And most of the time with SR turned off. But as you desribed it is a rare condition when i take the lens off and enable the SR and try to shoot. But it is important to be able to us every possible thing to help sharpen the image. I still think Pentax is making a bad mistake.

Also i always shoot with the 1.4 permantly attached. And when light is right the 2.0.
Very good info. How Does the Canon and Nikon deal with this issue? Do you know?

07-14-2010, 06:05 AM   #17
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QuoteOriginally posted by gary1952 Quote
Hey Lowell
Yes i agree. It sounds like meetering is the most important issue. I also shoot birds. And most of the time with a gimble head on the tripod. And most of the time with SR turned off. But as you desribed it is a rare condition when i take the lens off and enable the SR and try to shoot. But it is important to be able to us every possible thing to help sharpen the image. I still think Pentax is making a bad mistake.

Also i always shoot with the 1.4 permantly attached. And when light is right the 2.0.
Very good info. How Does the Canon and Nikon deal with this issue? Do you know?
To be honest, I simply don't know. It also depends on whether any outside lens makers pay licensing fees for the mounts and interface.

For the pentax interface, the solution at the TC level is relitively simple, it is simple encoding of a chip to do a translation, and it might even be possible (I have not given thought to it) to correct the aperture reporting by a simple pin translation.

But the problem is, I think really at the hands of the TC manufacturer's, to have the electronics incorporated into the TCs to correct the aperture reporting and focal length etc, the problem here is that I suspect this means processing power and time delay in the data feedback through pin 7 of the mount, where I believe all this data comes through.

As for shooting, your approach with the 300F2.8 is the same as mine with the 70-200F2.8 zoom, there is always a TC attached,

WIth respect to metering, the only issue is the K10D, my *istD and K7 both meter with and without the TC correctly, but even if they didn't the EV comp is applied in all modes including manual, so it would be simple to correct the open aperture metering. The K10D is the real problem with using a TC because i need to first of al correct the metering in auto modes with EV adjustment, and second, there is no EV adjustment applied in manual, so metering is always off.
07-14-2010, 06:40 AM   #18
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Hey Lowell
Im not going gripe to much. I am glad you are experienced in this area. I knew nothing of the meetering problem. I see where you are comming from when you are saying it is the Manufacturers problem for reporting. But i disagree in that with such a minor software change they could let there customers enjoy the very best of 3rd party manufactures. Because Pentax does not make big glass for us now.

I am very new to dslr photography. But not new with analog to digital conversions. I think i will look at the scan rates of the processor they are using. If i can find some info on them. That will tell me alot about the limits of there reporting process. Or the limitations of reporting if there are any.

In the old days with slow scan rates the processors could not handle changes very fast. But when i retired scan rates were at blazing speeds. Almost immediate. Scan rates in processor 5 years ago were running 50- 100s of scans per sec. Now i would suspect in the 100-1000 range for simple processing. But looking at the lcd screan and the coding envolved. The code may be very large and scan rates slowing accordinly. I am no expert by any means But this is a code related issue if i had to guess. Or processor related.

I have been thinking about the algorithems reqired to acomplish focus and setting all meetering and such and i think the processor is blazing fast to handle the processing of photos and related items. So why is this an issue... I am stumped..

I'll let you know if i read any good info on this if you want.
Here is a lind to some bird pics with the 300 and 1.4 and 2.0. Using mostly the K-7. And some with the k-20.

Jerry's Photo Galleries at pbase.com

I have ordered the sigma 500mm f4.5 and am waiting for it to clear customs now.. I can hardly wait.

Last edited by gary1952; 07-14-2010 at 07:06 AM.
07-14-2010, 09:15 AM   #19
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Gary, we're probably beating this issue to death, but...........

Think of it this way - the TC is basically a "pass-though" connector. The contacts in the TC are simply a direct connection between the lens and camera - there's no way for the camera to know there's something else "in the mix". The only way for the camera to know there's something else there would be for the TC to tell the camera. And that's not happening!

Now, having said all that, it would be fairly easy, I think, for Pentax to make a firmware change to allow the end user to change the lens' focal length even if it's been reported to the camera by the lens.

07-14-2010, 09:18 AM   #20
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QuoteOriginally posted by gary1952 Quote
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.
I'm not sure what the point of confusion is here, but it seems either you are not understanding something about the responses so far, or I'm not understand what you're asking. Sure, it would be possible for the camera to implement a system in which the *user* had the ability to override the focal length reported by the lens. What people are saying is *not* possible is for the *camera* to know if a TC is present. I am under the impression that you are claiming that *this* is the camera's fault. But it most definitely is not. The camera simply has no way of knowing whether you are using a TC, any more than knows if you've got a filter mounted, or are wearing the strap around your neck or not. Are you clear on this?

So the only solution would be to allow the user to override the report focal length, but the camera couldn't present this option just when a TC was mounted, because it doens't *know* when a TC is mounted. So the override would be available at all times. Realistically, I suspect this would end up in many people shooting themselves in the foot, forgetting to restore the default after removing the TC. I maybe guess the override could always turn itself off every time the camera shut off or detected a lens change? But then you'd have to remember to turn it back on if you *hadn't* actually removed the TC. Better than nothing, I suppose.
07-14-2010, 09:34 AM   #21
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There were some posts blaming the Sigma TC, but of course, my Tamron TC does no better. And of course, how does the Sigma or Tamron TC know what its being attached to. A manual optional menu in the camera could override it.

On the other hand, i've read that the in-body sensor movement SR are less effective at longer TC due to the amount of movement required. Not sure if this is true, but i sort of believe it due to some personal experience with the K10 and K20. I mainly rely on a tripod for longer FL or on a faster shutter. The advantage of a faster shutter is especially important for wild life movement in any case. Probably why Pentax hasn't done anything about it.
07-14-2010, 09:43 AM   #22
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Now I don't know what information travels through which connection, but would it be possible to block some of the connectors so you end up with the camera not getting a FL at all? that way, it would prompt you to dial it in manually for the SR. Not sure if it also uses the dialled in focal length for the other parameters it typically uses it for (flash and the like), but it might be a little hack to get the camera do what you want.
07-14-2010, 09:53 AM   #23
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I'll use it and not bitch.. I think it should be fixed but i am getting very good pics with the camera on my tripod. And if i take it off i pump up the shutter speed. Birds require rather high shutter speed and i really do not have that much problem. It just gripes me that the K-7 really gives the ability to change all other setting to my liking but not this one.
I just got a message from Pentax. I am going to ask them about it.
I will end here.
Thanks for all input.

07-14-2010, 12:35 PM   #24
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I'd still like to see confirmation as to whether you understand what we are saying about what is technically possible and not possible to fix, though. It is *not possible* - not now, not ever - for the camera to automatically detect the presence of the TC. It *is* possible for Pentax to design a menu system that would allow you the photographer to *tell* the camera there is a TC present.

So it's fine to say you think it should be fixed if you mean, to add the menu system, and I'd be happy to leave it at that too. But it just makes no sense whatsoever to say you think Pentax should do soemthing that absolutely positively 100% technically impossible to do - namely, to automatically detect the TC. So I just want to make sure you're not still thinking that this is possible.
07-14-2010, 02:07 PM   #25
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Lowell, I can help but think your metering issue with a TC is an anomaly. I can't recall any times using a TC with my K10D that I had to make any EV changes.
07-14-2010, 02:27 PM   #26
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QuoteOriginally posted by philbaum Quote
There were some posts blaming the Sigma TC, but of course, my Tamron TC does no better. And of course, how does the Sigma or Tamron TC know what its being attached to. A manual optional menu in the camera could override it.
actually there is

the pentax KAF and follow on mounts are pretty well documented.

starting from the lens locking pin and moving away, contacts 1,2 4,5,6 are aperture coding for min and max aperture, pin 3 is A mode selected on the lens, and pin 7 is the data pin where focal length, focusing distance etc are communicated

so, if there were electronics in the TC or as I suggested, some one looked at the aperture coding and determined a simple mechanical translation to do the TC conversion of 1 1.5 or 2 stops, the ap[erture could easily be corrected. Focal length would be more difficult because it would require more than a programmable chip or a pin translation , it would require communications.
QuoteQuote:
On the other hand, i've read that the in-body sensor movement SR are less effective at longer TC due to the amount of movement required. Not sure if this is true, but i sort of believe it due to some personal experience with the K10 and K20. I mainly rely on a tripod for longer FL or on a faster shutter. The advantage of a faster shutter is especially important for wild life movement in any case. Probably why Pentax hasn't done anything about it.
while I don't disagree, SR is not the only thing that uses focal length, it is used for program curves and shutter speed vs flash settings etc. anything that gets involves with exposure calculation in an automated way will use focal length. We had a thread a few weeks ago that in AV mode with a flash, shutter speed lower limit was absolutely set by the 1/focal length rule
07-14-2010, 02:32 PM   #27
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QuoteOriginally posted by Jodokast96 Quote
Lowell, I can help but think your metering issue with a TC is an anomaly. I can't recall any times using a TC with my K10D that I had to make any EV changes.
No, it was absolutely validated.

here is the exposure response as a function of aperture for different cameras.



the issue is that because exposure varries so much as a function of aperture , putting a TC on an F2.8 lens, and leaving the camera to think it is still F2.8 and not F4 results in a tendancy to over expose, because the response at F2.8 is lower than that at F4 or 5.6.

the camera compensates this non linearity out in calculation, that is why the K10D and K20D are so bad when using a TC on a fast lens. Now if you put a TC on a slow lens, it may not be noticible because the tendancy beyond F5.6 is pretty much constant.

Note, this was measured shooting a uniformly lit wall, and then average greyscale plotted. each greyscale of 45 is one stop when you are within +/-80 of the middle (i.e. 125)
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