Kenko Pro 300 2x, so what happens?


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AReality

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#1
How's the image quality using the Kenko Pro 300 2x with a EF 75-300mm lens?
Did a search and some said cannot auto-focus due to loss of 2 f-stops... also need at least F2.8 to focus...

Or is a 1.4x enuff already?
Just wanna some opinion from U guys 1st...


Thanks... ;)
 

mervlam

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#2
AReality said:
How's the image quality using the Kenko Pro 300 2x with a EF 75-300mm lens?
Did a search and some said cannot auto-focus due to loss of 2 f-stops... also need at least F2.8 to focus...

Or is a 1.4x enuff already?
Just wanna some opinion from U guys 1st...


Thanks... ;)
yup. if you want to use a 2x converter, your lens needs to have a max aperture of f/2.8, or chances are that the camera cant AF

I think focusing will not achieved even with the 1.4x converter. at f/8, the camera simply cant AF as it's "too dark".

why would you want a 150-600mm f/8-11 or a 105-420mm f/5.6-8?
 

E-Lim

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#3
EF 75-300mm we know is not very sharp, get 1.4X to make it 105-420mm so that will not sacrifice the photo quality. For 2X TC you will definitely loose sharpness.
 

AReality

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E-Lim said:
EF 75-300mm we know is not very sharp, get 1.4X to make it 105-420mm so that will not sacrifice the photo quality. For 2X TC you will definitely loose sharpness.
But I dun think it's correct to compare
focal length at 420mm with 1.4x TC,
with focal length at 600mm with 2x TC.

But I think should compare the quality with
focal length at 420mm with 1.4x TC,
with focal length at 420mm with 2x TC.

are both the quality the same?

My maths not very good... But is the max f-number the same for both TCs when zoom to the same focal length?
 

Bluestrike

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#5
AReality said:
But I dun think it's correct to compare
focal length at 420mm with 1.4x TC,
with focal length at 600mm with 2x TC.

But I think should compare the quality with
focal length at 420mm with 1.4x TC,
with focal length at 420mm with 2x TC.

are both the quality the same?

My maths not very good... But is the max f-number the same for both TCs when zoom to the same focal length?
Even if you compare the thing at the same focal len, your 420mm, the 1.4TC will def stand out sharper then the one with the 2xTC.

Well for the 1.4TC, the 420mm is the max focal length, so that will be at F5.6 + 1 stop. for the 2xTC, at 420mm, the F-stop is not at F5.6 so you have to see what the F-stop at 210mm then + 2 stop.
 

megaweb

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#6
TC should work similar like this

If your lens quality is very very sharp,

with 1.4x TC , it should have very sharp quality
with 2x TC , it should have sharp quality

so imagine if you have sharp lens like 75-300mm , what should you get after using TC ?
 

AReality

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#7
megaweb said:
TC should work similar like this

If your lens quality is very very sharp,

with 1.4x TC , it should have very sharp quality
with 2x TC , it should have sharp quality

so imagine if you have sharp lens like 75-300mm , what should you get after using TC ?
Teacher, my answer:

Since my lens is sharp,
with 1.4x TC , it should have quality.
with 2x TC , it should have.

correct?
 

Bluestrike

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#8
AReality said:
Teacher, my answer:

Since my lens is sharp,
with 1.4x TC , it should have quality.
with 2x TC , it should have.

correct?
THE BEST IS!!!

COME DOWN TO SEED TML!

I'l bring both the 1.4TC and 2xTC then you judge for yourself!

:devil:
 

E-Lim

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#9
AReality said:
Teacher, my answer:

Since my lens is sharp,
with 1.4x TC , it should have quality.
with 2x TC , it should have.

correct?
1.4X TC quality is better than 2X. Period.
 

mervlam

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#10
megaweb said:
TC should work similar like this

If your lens quality is very very sharp,

with 1.4x TC , it should have very sharp quality
with 2x TC , it should have sharp quality

so imagine if you have sharp lens like 75-300mm , what should you get after using TC ?
to answer on behalf of "cher"

with 1.4x, okay only
with 2x, sucks

my point: dont bother using TC with that lens (btw, i own one, which i think it's not even considered sharp)
 

mervlam

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#11
Bluestrike said:
THE BEST IS!!!

COME DOWN TO SEED TML!

I'l bring both the 1.4TC and 2xTC then you judge for yourself!

:devil:
agree agree.... :blah: :devil:
 

HelmetBox

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#12
If my lens is a 70-200 f2.8, will the 2X and 1.4X converters differ?

If the f stop remains unchanged,

will the quality differ at 150mm on the lens, which is
-210mm on the 1.4X ?
-300mm on the 2X ?

How about
-210mm on the 1.4X (150mm on lens)
and
-210mm on the 2X (105mm on lens)

Does the brand of the TC matter? I'm using a sigma lens EX HSM for canon, so should I go for canon or sigma TCs?

Please advise.......
 

mervlam

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#13
HelmetBox said:
If my lens is a 70-200 f2.8, will the 2X and 1.4X converters differ?

If the f stop remains unchanged,

will the quality differ at 150mm on the lens, which is
-210mm on the 1.4X ?
-300mm on the 2X ?

How about
-210mm on the 1.4X (150mm on lens)
and
-210mm on the 2X (105mm on lens)

Does the brand of the TC matter? I'm using a sigma lens EX HSM for canon, so should I go for canon or sigma TCs?

Please advise.......
the quality of the 1.4x is relatively better than the 2x. it doesn't matter at what focal length. the job of the teleconverter is just to magnify the image by the magnification factor.

get the Sigma 1.4x APO EX.

Reference: http://www.sigmaphoto.com/html/pages/70_200_ex.htm
 

Knighthunter

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#15
HelmetBox said:
Does the brand of the TC matter? I'm using a sigma lens EX HSM for canon, so should I go for canon or sigma TCs?

Please advise.......
Canon TC price is 3/4 or more of your sigma lens' price......
 

megaweb

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#16
Please take notes :

Kenko TCs support Canon-EOS, Nikon-AF-D, and Minolta-AF lens
see http://www.thkphoto.com/products/kenko/slrc-01.html

Sigma TCs support Sigma lens only (Sigma Canon-EOS mount, Sigma Nikon-AF-D mount, Sigma Minolta-AF mount and Sigma Pentax AF mount lens)
see http://www.sigmaphoto.com/html/pages/ConvComptChart.htm

Canon TCs support Canon L lens (fixed focal length lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, and 100-400 f/4.5-5.6L IS zoom lenses ) only
see http://www.usa.canon.com/eflenses/lenses/ef_14x/ef_14x.html
and http://www.usa.canon.com/eflenses/lenses/ef_2x/ef_2x.html
 

HelmetBox

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#17
Okay, so in my understanding (Please do correct me if I'm wrong):

-The 1.4X TC will reduce effective aperture by 1 stop (2.8 -> 3.2)
-The 2.0X TC will reduce effective aperture by 2 stops (2.8 -> 3.5)
-need for f/stop compensation depends on coupled lens
-Compatibility solely depends on TC type and manufacturer
-Quality of 1.4X is better than 2X
-Autofocus is only possible if the aperture of your lens is big to begin with as light reaching your sensors are reduced with the TC attached

Am I on the right track? :sweat:
 

mervlam

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#18
HelmetBox said:
-The 1.4X TC will reduce effective aperture by 1 stop (2.8 -> 3.2)
-The 2.0X TC will reduce effective aperture by 2 stops (2.8 -> 3.5)
f/2.8 to f/4.0 -> 1 stop
f/2.8 to f/5.6 -> 2 stops

you multiply the aperture f number by sqrt(2) (which is 1.4) for one stop. that means you multiply by 2 for two stops.



HelmetBox said:
-need for f/stop compensation depends on coupled lens
-Compatibility solely depends on TC type and manufacturer
-Quality of 1.4X is better than 2X
-Autofocus is only possible if the aperture of your lens is big to begin with as light reaching your sensors are reduced with the TC attached

Am I on the right track? :sweat:
yup, i think :D
 

Knighthunter

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#19
HelmetBox said:
Okay, so in my understanding (Please do correct me if I'm wrong):

-The 1.4X TC will reduce effective aperture by 1 stop (2.8 -> 3.2)
-The 2.0X TC will reduce effective aperture by 2 stops (2.8 -> 3.5)
f/2.8 + 1.4x = f/4
f/2.8 + 2 x = f/5.6

f/4 + 1.4x = f/5.6
f/4 + 2 x = f/8
 

HelmetBox

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#20
mervlam said:
f/2.8 to f/4.0 -> 1 stop
f/2.8 to f/5.6 -> 2 stops

you multiply the aperture f number by sqrt(2) (which is 1.4) for one stop. that means you multiply by 2 for two stops.





yup, i think :D
rms value? hehe kidding. :D

Now I know....... interesting.
 

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