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Forum: Pentax News and Rumors
09-30-2012, 07:38 PM
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wooww K5IIs compare to 24MP FF, i guess from sony alpha A-850? :) because recent 24MP FF camera not yet tested :)
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Forum: Pentax News and Rumors
09-14-2012, 07:26 AM
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how about FF in GXR module with K and M mount ?? call it Ricoh Pentax FF - just guess
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Forum: Pentax SLR Lens Discussion
08-02-2012, 09:21 PM
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Thanks for the respons, now its bit clear to me, thanks for the explanation..
anyway here are another sample why i guess the f stop - being increase about 1.5-2 stop. I tested with same aperture and speed but different Iso:
note: pic at 300mm without tc - cropped and resize to 900x596
pic with 300mm + TC only resize to 900 x 596 (slightly out of focus)
pic at 190mm + 1.6x TC (304mm) cropped and resize to 900x596
300mm No TC - f/11 - 1/200sec - Iso 100 (crop & resize)
300mm no TC - f/5.8 - 1/200sec - Iso 100 (crop & resize)
300mm with TC - f/5.8 - 1/200sec - Iso 400 (resize only)
190mm + 1.6x TC (304mm) - f/5.6 - 1/200sec - Iso 200 (crop & resize)
300mm + TC f/5.8 - 1/200 sec - iso 800 (resize only)
Pic 2,3,4 are almost similar exposure (pic 3 and 4 slightly brighter in my monitor)
Pic 2 vs 3 has two stop different Iso 100 vs Iso 400
Pic 2 vs 4 has one stop different iso 100 vs iso 200 but pic 4 has slightly larger aperture f/5.6 vs 5.8
i think the conclusion base on this test:
at the same FL 300mm or 190+TC (304mm) it has around 1 stop slower
at the longest FL 300mm vs 300+TC (480mm) it has around 2 stop slower
Rai - Bali
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Forum: Pentax SLR Lens Discussion
08-01-2012, 09:30 PM
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Hi Dave,
yess, this TC has about 26mm real element, its same size as lens f/2.8 (Tamron 17-50 or pentax 50-135), even 55-300 (f/4.0-5.8) has only 18mm rear element. And Rear elements lens 50mm f/1.4 is about 30mm.
do you mean if i attached another TCs- Canon TC-DC58A (real elements 48mm) into 55-300 the effective f-number will increase to f/6.2, because of 300/48? how about tamron 17-50 and pentax 50-135? both has same size of rear and front elements but different FL?
I agree of lost light and about 1.5-2 stops slower but i am not sure if the effective f-number now becomes f/11?
Anyway here is another sample - DOF comparison ( tried to shot at same dimension/size, in exactly same position with tripod, unable to set the same aperture) but i dont know why the FL is 30mm different. Anyway if we look at DOF comparison, it is unlike f/5.8 vs f/11?
300mm f/5.8 - 1/640sec iso 800 around 5m to target.
170mm + 1.6x (270mm) f/5.6 - 1/640 - Iso 800
Crop 100% : 300mm f/5.8 - 1/640sec iso 800 around 5m to target.
Crop 100% : 170mm + 1.6x (270mm) f/5.6 - 1/640 - Iso 800
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Forum: Pentax SLR Lens Discussion
07-25-2012, 08:46 AM
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moon shots
f/10 - 1/200sec - Iso 800 - with tripod
55-300 + TC, at 300mm (ca 480mm) ... crop 62% to get size equivalent with 300mm crop 100%
edit: sharpening ...
several test without TC at 300mm, can't get better result than this when crop 100%...
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Forum: Pentax SLR Lens Discussion
07-25-2012, 02:15 AM
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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.
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Forum: Pentax SLR Lens Discussion
07-23-2012, 07:49 PM
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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.
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Forum: Pentax SLR Lens Discussion
07-23-2012, 09:15 AM
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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
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Forum: Pentax SLR Lens Discussion
07-23-2012, 08:46 AM
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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.
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Forum: Pentax SLR Lens Discussion
07-23-2012, 07:51 AM
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Ok ... here is the camera with TC
At 300mm - f/5.8 - 1/500sec - Iso 100 full size
At 300mm + 1.6x TC f/5.8 1/125 - Iso 100 full size
Without TC crop 100%
With TC crop 100%
At 300mm f/5.8 - 1/800sec - Iso 100 full size
At 300mm + 1.6x TC f/5.8 1/160 - Iso 100 full size
Without TC crop 100%
With TC Crop 100%
k5 with another TC
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Forum: Pentax SLR Lens Discussion
07-23-2012, 07:44 AM
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similar result with or without TC, but slightly more CA with TC (very little) ... at native 300mm, i use AF, with TC I do manually .. all test handheld, so you can see the result... can see my posting at dpreview. tested with another TCs, the result was soft at longest FL..
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Forum: Pentax SLR Lens Discussion
07-23-2012, 07:03 AM
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Forum: Pentax SLR Lens Discussion
07-23-2012, 01:59 AM
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Just tested 55-300 + canon TC-DC52B 1.6x ... result is sharp and great. 1-2 stop slower but its fine for such combination ...
can AF until original 260mm + TC (ca. 400mm) must manual at 300mm * TC (480mm) and NO vignetting !!
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Forum: Welcomes and Introductions
01-24-2012, 10:31 AM
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Hi everyone, greeting from Island of god - Bali.
K-5 is my first pentax camera, sofar so good. Longtime nikon user (d100,d200,d300) switch to Pentax for good reasons, proud to be pentax user. Anyway if you need some information about photo spots in Bali or Indonesia, please feel free to contact me.
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