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05-23-2013, 03:45 PM   #16
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I forgot about the change in aperture when adding a teleconverter. Thanks for reminding me.

06-05-2013, 08:12 PM   #17
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Welll, I've decided to return the teleconverter. I believe it's faulty and one of the reasons it sold at such a low price. I tested it on two different lenses and neither would meter right with the TC attached. I cleaned the lens and TC contacts but it made no difference. So, it goes back and I'll buy the vivitar one next week.
06-05-2013, 09:28 PM   #18
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QuoteOriginally posted by boriscleto Quote
I can definitely recommend the Vivitar, it seems to be the same as the Tamron
it seems to be the same because it is the same, tamron produces those for Vivitar. The difference is the tamron version has the hsm power riser in the TC active and the vivitar one inactive. when they first started producing those, the vivitar one also had the active HSM riser but then they stopped producing them that way, now even though the riser is still present in the vivitar, it is not power connected and thus can only be used with screw drive AF lenses.

The Tamron/Vivitar TC has really good IQ and really shines when using high resolving glass (upper tier glass). I am currently using the Sigma 1.4 DG TG and it is outstanding with my Sigma 300 2.8 - it matches so well with the 300 2.8 I usually shoot wide open with that combo and it gives me outstanding results @ 420mm f/4.
06-05-2013, 10:44 PM   #19
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QuoteOriginally posted by photolady Quote
Welll, I've decided to return the teleconverter. I believe it's faulty and one of the reasons it sold at such a low price. I tested it on two different lenses and neither would meter right with the TC attached. I cleaned the lens and TC contacts but it made no difference. So, it goes back and I'll buy the vivitar one next week.
What camera are you using. If it is a K10/20 then it simply won't meter correctly with any TC that simply transmits the aperture value without correction

The metering on all cameras is somewhat compensated as a function of maximum aperture, but the K10 and K20 are really unique in terms of the non linearity in metering if the native aperture is not known

I did a lot of work on this when I got my K10.



06-05-2013, 11:15 PM   #20
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I;m using a K-x.
And thanks for the information. I guess unless I buy a high end lens, I'm stuck with no real metering, right? I miss my film days.
06-06-2013, 02:18 PM   #21
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QuoteOriginally posted by photolady Quote
I;m using a K-x.
And thanks for the information. I guess unless I buy a high end lens, I'm stuck with no real metering, right? I miss my film days.
Not quite right. When I ran into this trouble, i had just gotten my K10 and was having fits with exposure. My *istD was great with my AF lenses and pretty good, as you can see with K mounts, although it did drift up just a little from perfect exposure to stopped down fully ( perhaps overall +/-1/2 stop from the average value. You can see how good an A series lens was, from the A 50/1.2 that Bende8 tested. I can tell you my sigma 70-200/2.8 (which is high end) has a total variance that is likely within the realm of measurement error of less than 1/10 of a stop, so yes, high end glass can be pretty accurate, BUT, my Tammy 28-75/2.8. Also high need, drifts upwards from nothing to 1 stop over at min aperture due to the mechanism they used.

Now put a TC on my sigma with the K10 and with a 1.4x I am +.7 stops over exposed at all apertures, and +1.3 over with then2x TC. All because of the aK10s bad metering. The only good thing is that at least with an A lens the error is constant over all apertures, so once you learn the error, you just dial it in
06-06-2013, 03:42 PM   #22
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As Lowell said, not quite right. BTW: My reference to upper tier glass and a TC was just really in reference to IQ and nothing else.

One thing you can do is use the cameras light meter to take the guess work out of it - switch to hyper manual mode and green button meter, this will measure the light through the lens tc combo and set the optimum exposure settings for you.
06-06-2013, 10:26 PM   #23
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QuoteOriginally posted by joe.penn Quote
As Lowell said, not quite right. BTW: My reference to upper tier glass and a TC was just really in reference to IQ and nothing else.

One thing you can do is use the cameras light meter to take the guess work out of it - switch to hyper manual mode and green button meter, this will measure the light through the lens tc combo and set the optimum exposure settings for you.
Joe. Becareful with this approach, because the camera is not perfect. The cameras are all calibrated to give a correct metering with a known aperture, and as my tests show, this is not always accurate when aperture is unknown, although some bodies like the K10D are much worse than others

I ultimately have tested a large portion of my lens collection to havew an exact curve for the lens on each body

This takes time, about 1/2 hour per lens, but is well worth it. I use a block wall uniformly lit by sunlight, to do this test, and check the lens at each aperture click, and also if it is an A lens or newer, at each aperture set by the camera. It is interesting to know how each lens behaves in advance because it removes problems later when shooting. I would much rather spend 1/2 hour once on each lens when I get it, than 1/2 hour per photo in post processing trying to fix the exposure etc, and recover things because the lens didn't do what I wanted.

Simply put, the camera is a tool, but even the bes tools and instruments need to be calibrated


Last edited by Lowell Goudge; 06-06-2013 at 10:32 PM.
06-07-2013, 01:16 AM   #24
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QuoteOriginally posted by joe.penn Quote
switch to hyper manual mode
How would I set this in a K-x. I can find nothing in the manual about this setting.

QuoteOriginally posted by Lowell Goudge Quote
This takes time, about 1/2 hour per lens, but is well worth it. I use a block wall uniformly lit by sunlight, to do this test, and check the lens at each aperture click, and also if it is an A lens or newer, at each aperture set by the camera. It is interesting to know how each lens behaves in advance because it removes problems later when shooting. I would much rather spend 1/2 hour once on each lens when I get it, than 1/2 hour per photo in post processing trying to fix the exposure etc, and recover things because the lens didn't do what I wanted.
Thanks Lowell, I will give this a try also. Now I have the new tripod it should help me to accomplish this without myself getting tired from standing up so long and holding the lenses.
08-02-2013, 07:22 AM   #25
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Sorry for such a long wait in answering. I have decided to send that tc to my friend and fellow member Wildred5273 for him to play around with and i'm going to order the Vivitar one. Went over there to Adorama to order it today and guess what? it's on backorder....
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