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07-23-2012, 08:16 AM   #16
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results are suprisingly good

couple of interesting things I notice though,

it appears that the lens on it's own had a focusing error for the shots of the post, there is no way the shots with converter should be sharper than the lens on its own.

there is also an exposure error / difference between the converter + lens compared to the lens. the shooting data suggests 2 stops difference, but the shots with the TC are brighter, suggesting that the light loss is less than 2 stops,.by measuring grey scale value this appears to actually be, about 1/3 stop error/difference in exposure was this done using manual exposure or metered by the camera, and if by the camera what camera? either this or the EV steps were at .5 as opposed to .3 and the camera could not get a better exposure fit.

Magnification is just about spot on in the ratio, I measured 1.61x based on scaling the subjects.

07-23-2012, 08:46 AM   #17
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thanks ... yess i noticed f stop becomes slower, sample was tested with AV mode. When i tested with M mode - with TC tends to underexposed, it was not surprise but its still sharp, similar as without TC..
If you know some really good TCs (you called it magnifier) (like Nikon TC-E17ED or 15ED or Canon TC-DC58A) its not as simple magnifier lens or cheap TC, it has five element glass with 1 or 2 ED glass, its really good TCs. Its not surprise for me if the result is as sharp as without TCs.
07-23-2012, 08:51 AM   #18
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raimaster: Wow. That looks much better than I thought it would. :-)
07-23-2012, 09:15 AM   #19
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another test with M Mode:
300mm f/6.3 - 1/200sec - Iso 100:

Noted: without TC shot with AF, with TC shot manual..
CA is very minimal for kind of shot..

full size without TC


full size with TC


crop 100% without TC


crop 100% with TC


07-23-2012, 11:27 AM   #20
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Thanks for posting the images; a brief test shows the converter's image is substantially better than the image shot with no converter and subsequently enlarged to the same size (assuming the converter-less shot was in focus, etc.)


This is the best 100% performance I've seen for a converter (either front or rear, cheap or dear) on the DA 55-300 at 300mm. I had previously tested the Oly 1.7x and Nikon 15ED front TC's. - their performance was not so good as shown here.

Top with canonTC-DC52B, Bottom without TC, enlarged to match,



Thanks for the info,
Dave in Iowa

I'm going to buy one right now.

Last edited by newarts; 07-23-2012 at 12:53 PM.
07-23-2012, 02:41 PM   #21
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QuoteOriginally posted by newarts Quote
I'm going to buy one right now.
I'm about half tempted to pick one up myself!
07-23-2012, 03:10 PM   #22
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Looks like it's been discontinued, but I found it for $41 here: Canon TC-DC52B
07-23-2012, 03:45 PM   #23
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Unlike rear teleconverters, they don't eat any light. Of course, they're limited to mounting on lenses of a sufficiently small objective.

07-23-2012, 07:49 PM   #24
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yup, i have anothers Tcs, from Opteka, Canon TC-DC58A, Nikon TC-E15ED and Sony VCL-HGD1758, they are good tcs but did not perform well with 55-300, Either too heavy and soft at the longest FL, TC-DC52B is exceptional good and very light compare to those converter.
07-24-2012, 10:50 PM   #25
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Thanks for sharing this, rainmaster
07-25-2012, 12:48 AM   #26
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QuoteOriginally posted by alphanerd Quote
Unlike rear teleconverters, they don't eat any light. Of course, they're limited to mounting on lenses of a sufficiently small objective.
Well any glass put in front of the sensor will eat light and that is clearly demonstrated here in the 2 stop reduction of shutter speed.



Rai - thanks for posting those images and introducing us to these magnifiers/TCs whatever you want to call them ! I am truly shocked at the results.

I have done some testing with the 55-300 and TCs here : https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/139941-lenses-...-x1-4-etc.html

It was interesting to note though that on DPR you said you manually focused. So were these shot using AF or MF ?

Thanks again !
07-25-2012, 01:59 AM   #27
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I found one in UK on clearance for £36. Now I only need a 55-300 for my safari trip.

Seb

Edit: Or on my F70-210...

Last edited by bassek; 07-25-2012 at 02:18 AM.
07-25-2012, 02:15 AM   #28
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QuoteOriginally posted by Frogfish Quote
Well any glass put in front of the sensor will eat light and that is clearly demonstrated here in the 2 stop reduction of shutter speed.



Rai - thanks for posting those images and introducing us to these magnifiers/TCs whatever you want to call them ! I am truly shocked at the results.

I have done some testing with the 55-300 and TCs here : https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/139941-lenses-...-x1-4-etc.html

It was interesting to note though that on DPR you said you manually focused. So were these shot using AF or MF ?

Thanks again !
All shots without TC is AF.
With TC the AF can work properly only until around 260mm (ca.400mm)

just visit your comparison test, nice work ... thanks for sharing.
07-25-2012, 02:35 AM   #29
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QuoteOriginally posted by raimaster Quote
All shots without TC is AF.
With TC the AF can work properly only until around 260mm (ca.400mm)

just visit your comparison test, nice work ... thanks for sharing.
Thanks Rai.

The 260mm limit for AF shouldn't be an issue though since from my experience the 55-300 is sharper at 240-260mm and cropping to a 300mm FoV is still sharper than shooting at 300mm.
07-25-2012, 06:48 AM   #30
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QuoteOriginally posted by raimaster Quote
thanks ... yess i noticed f stop becomes slower, sample was tested with AV mode. When i tested with M mode - with TC tends to underexposed, it was not surprise but its still sharp, similar as without TC...
The reason for the exposure error? is that the camera needs to know the true open aperture value, because it has a non linearity that is a function of aperture. since metering is at open aperture, the true maximum aperture is important. that is why there has been such a discussion in the past about poor metering with manual aperture lenses, the camera does not know the aperture and therefore cant correct.

Here it is metering as if it has the lens with no TC, and therefore is not applying the correct factor. I did a lot of work on this issue over thepast 4-6 years, starting with comparing the K10D to the *istD, etc,
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