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08-04-2011, 05:01 PM   #1
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Stacking Teleconverters

Quick question, has anyone stacked the 1.4X and 2X adaptall 2 teleconverters? Is there an advantage to having one in front of the other?

08-04-2011, 05:31 PM   #2
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I have stacked the non-adaptall 1.4x and 2x teleconvertors and the combination works fine in broad daylight (remember you will lose about 3 stops)
08-04-2011, 06:03 PM   #3
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I've used a 2x and a 1.7 AFA on a 600mm mirror for moon shots... The moon doesn't fit in the frame..lol. Had the 1.7AFA on the camera body, then the 2x+mirror, The AFA worked fine to fine tune the MF of the mirror once I got close to focus.
08-05-2011, 10:50 PM   #4
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QuoteOriginally posted by cmohr Quote
I've used a 2x and a 1.7 AFA on a 600mm mirror for moon shots... The moon doesn't fit in the frame..lol. Had the 1.7AFA on the camera body, then the 2x+mirror, The AFA worked fine to fine tune the MF of the mirror once I got close to focus.
You must be mistaken about AFA 1.7x working with 2x TC on a 600mm mirror lens. Even if your mirror lens is a fast f5.6 with the two TCs combined your aperture will be f20.72 and if the lens is the conventional f8.0 then the effective aperture will be f29.6. I've combined AFA 1.7x, Tamron PZ-AF 2x TC with Tamron SP 60B, 300/2.8 on a K20D (effective maximum aperture of f10.36) and I wasn't able to get focus confirm in the viewfinder. And I was shooting at around 4:00pm on a hot, bright day.

It would be great if AF would work at f21 or f30 but my own experience and the vast majority of the forum members' experience would indicate otherwise.

Edit: I should have multiplied the two TCs and the lens' maximum aperture. If the lens' native aperture is f5.6 then combined effective aperture is 5.6*2*1.7=19.04 and at f8.0: 8*2*1.7=27.2.

Thanks,


Last edited by excanonfd; 08-05-2011 at 11:07 PM. Reason: bad math
08-06-2011, 05:56 PM   #5
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QuoteOriginally posted by excanonfd Quote
I should have multiplied the two TCs and the lens' maximum aperture.
So if my lens is an f2.8 then multiply that X1.4(for converter A) = f3.9 then X2(for converter B) = f7.84 max aperture on my now 840mm(started at 300mm) lens??
08-06-2011, 11:00 PM   #6
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QuoteOriginally posted by littledrawe Quote
So if my lens is an f2.8 then multiply that X1.4(for converter A) = f3.9 then X2(for converter B) = f7.84 max aperture on my now 840mm(started at 300mm) lens??
My thinking is that since the focal length is being multiplied by the TC's conversion factor, shouldn't the aperture value be multiplied? Answering your original question, stacking AFA1.7x and PZ-AF 2x to a Tamron 60B, I got focal length of 1020mm at f9.52 but IQ suffers too drastically, imo. It was hard to focus - I turned off AF indicator/confirmation and used micro prisms to focus. I was trying to reach distant subject, this combination might be more respectable with closer subjects. I'll give this a try on Sunday.

Thanks,
08-07-2011, 02:40 AM   #7
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QuoteOriginally posted by excanonfd Quote
You must be mistaken about AFA 1.7x working with 2x TC on a 600mm mirror lens. Even if your mirror lens is a fast f5.6 with the two TCs combined your aperture will be f20.72 and if the lens is the conventional f8.0 then the effective aperture will be f29.6. I've combined AFA 1.7x, Tamron PZ-AF 2x TC with Tamron SP 60B, 300/2.8 on a K20D (effective maximum aperture of f10.36) and I wasn't able to get focus confirm in the viewfinder. And I was shooting at around 4:00pm on a hot, bright day.

It would be great if AF would work at f21 or f30 but my own experience and the vast majority of the forum members' experience would indicate otherwise.

Edit: I should have multiplied the two TCs and the lens' maximum aperture. If the lens' native aperture is f5.6 then combined effective aperture is 5.6*2*1.7=19.04 and at f8.0: 8*2*1.7=27.2.

Thanks,
well, it worked perfectly, remember, the moon is the nights sun, and I was pointed directly at it.
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08-07-2011, 03:17 AM   #8
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QuoteOriginally posted by excanonfd Quote
stacking AFA1.7x and PZ-AF 2x to a Tamron 60B, I got focal length of 1020mm at f9.52 but IQ suffers too drastically
Tried with AF1.7x + 01B(2x,tamron)+tamron 360B,arrived at figures same as
what you have.Played around with it and some backlit trumpeter swans.
Wasnt real serious,dont recall using autofocus.Have image in 300mmplus thread.
Very soft.Real cumbersome too,length and weight on mount(s) was major concern.
Didnt expect too much,seems IQ suffers,as you say.

08-07-2011, 04:02 AM   #9
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There also tends to be an image quality drop off with converters as well the already mentioned light disadvantage, both of which would be further multiplied by the addition of additional converters.

For me if big magnification is required on a regular basis, I would just go buy bigger glass.
08-07-2011, 02:32 PM   #10
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QuoteOriginally posted by cmohr Quote
well, it worked perfectly, remember, the moon is the nights sun, and I was pointed directly at it.
The moon may be the nights' sun but it pales in comparison with daylight. Your moon shot according to the exif file was shot at 1/20 sec, ISO 800. I took meter readings at 1:30pm (bright, sunny day) with my Pentax Spotmeter V at ISO 800 on my neighbour's gray asphalt shingle roof: I got readings of 1/1000@f16, 1/500@f22, 1/250@f32, your 600mm mirror lens with the AFA1.7x and 2x TC, would be in the aperture range I've listed above.

I mounted on my K20D, AFA1.7x, Tamron PZ-AF 2x TC, Tamron 55B 500/8.0 mirror lens at ISO 800. No matter what I pointed the camera at I could not achieve focus lock. Here is a picture of someone's white picket railings (probably as contrasty as one can get) and still no focus lock. Irfanview image viewer strips the exif when converting raw to jpg; 1/1000sec, ISO800, f27.2 (calculated), 2sec shutter delay on a tripod with SR off.

Maybe in OZ Pentax cameras work exceptionally well.

Thanks,

Last edited by excanonfd; 10-11-2011 at 11:39 AM.
08-07-2011, 02:45 PM   #11
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QuoteOriginally posted by excanonfd Quote
Irfanview image viewer strips the exif when converting raw to jpg;
Try Faststone Image Viewer -- also very capable freeware -- and no EXIF stripping, plus many useful features in Ver 4. Easily handles anything I want to do for web images and general browsing.

H2
08-07-2011, 02:54 PM   #12
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Thanks pacerr, that's good to know. I'll give FastStone a try.

Edit: Just tried it, conversion is slower than Irfanview and the picture was brightened up considerably but I did not set anything except for resize in the advance options:

Last edited by excanonfd; 10-11-2011 at 11:39 AM.
08-07-2011, 03:56 PM   #13
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@ excanonfd

Play with it (FSIV) for a while. Explore the "left side of the screen" options and the menu bar for image adjustments. In fact, hit all four sides of the screen with the mouse and the Help mode tag for additional work bars/image info. Right click on everything you see -- many surprises there. Re-directs to other, more robust, programs too.

This is easily the equivalent of the Express Mode in the other major SW players (although with a little less finesse -- likely attributed to SW copy right issues) and it's free. Good enough that I contribute for each version I use.

H2
08-09-2011, 02:05 AM   #14
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QuoteOriginally posted by cmohr Quote
well, it worked perfectly, remember, the moon is the nights sun, and I was pointed directly at it.
That's true:

Full moon EV 14
Gibbous moon EV 13
Half moon EV 12

valid when aimed at with a LONG lens...

But even mirror lock up, cable release and rock solid tripod can't give you more then maybe 2-3 out of 10 usable pictures of the moon (my experience). And excellent pictures need a entirely different setup, with a telescope involved.

I wouldn't stack teleconverters apart from sun/moon shots.

Just my 2 cents.
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