180/2.8 w kenkopro 1.4x or 300/4


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surge

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hi guys,

i have a 180/2.8 and a kenkoPro 1.4x convertor. which gives me about 270/4.

i am thinking of getting a 300/4 lately.

is the 300/4 much better than 180/2.8 w convertor? thanks
 

eawtan

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TMC said:
just get the 300/4, gadrian`s one is at a pretty good price.
I'd rather get the AFS 300/4 (if I didn't already have something in this range).
 

gadrian

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I personally dislike teleconvertors.. but the best is to make a real comparison and then decide..
 

surge

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thanks for the link! very very useful for me. :)
 

mpenza

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From the article, it seems that 180/2.8+kenko pro 1.4x is a very good match optically vs the 300/4. only that the focussing will be slower.

I'm in a similar situation too (even though i'm using canon ;p). I'm using a 200/2.8L + Kenko Pro 1.4x to "replicate" a 300/4L. Advantage will be lower cost and lighter setup but at some expense to focussing speed (even though 200/2.8L has USM) and I believe some degradation optically.
 

lsisaxon

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mpenza said:
From the article, it seems that 180/2.8+kenko pro 1.4x is a very good match optically vs the 300/4. only that the focussing will be slower.

I'm in a similar situation too (even though i'm using canon ;p). I'm using a 200/2.8L + Kenko Pro 1.4x to "replicate" a 300/4L. Advantage will be lower cost and lighter setup but at some expense to focussing speed (even though 200/2.8L has USM) and I believe some degradation optically.
My opinion is that although a teleconverter is useful, I feel that it can never match a lens designed to perform at a longer focal length. Any aberration of the original lens would be effectively multiplied also. Plus, however well the teleconverter is designed, it will add more elements, which adds more surfaces for the light to scatter and more diffractive error. But considering the price you pay for it, then it would be useful. But if you ever foresee that you need a longer lens very often, then it would make sense to get the longer lens, otherwise, a TC would probably suffice.
 

mpenza

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lsisaxon said:
My opinion is that although a teleconverter is useful, I feel that it can never match a lens designed to perform at a longer focal length. Any aberration of the original lens would be effectively multiplied also. Plus, however well the teleconverter is designed, it will add more elements, which adds more surfaces for the light to scatter and more diffractive error. But considering the price you pay for it, then it would be useful. But if you ever foresee that you need a longer lens very often, then it would make sense to get the longer lens, otherwise, a TC would probably suffice.
Yup, definitely. If a longer lens is needed more often, it definitely makes more sense to get it. For me, I seldom need 280 or 300mm focal length and the 200/2.8L+1.4x makes a pretty good and useful alternative.
 

roti_prata

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i often use a borrowed nikkor 300/2.8 + tc1.7 when im shooting planes at the airport(past-time)

the benefit of using 180/2.8 + tc1.4 is tt u can hav f2.8 when u need it while the 300/4 is fixed

many of my dawn and night shots were made w/o the tc and then cropped, which proved more effective thn getting blurred pics half the time when at f4
 

Cheesecake

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roti_prata said:
the benefit of using 180/2.8 + tc1.4 is tt u can hav f2.8 when u need it while the 300/4 is fixed

many of my dawn and night shots were made w/o the tc and then cropped, which proved more effective thn getting blurred pics half the time when at f4
Brother!!

stack a T.C on a f2.8 lens and u can still shoot at f2.8?
not so sure about what u've gone through becos from my limited knowledge of T.Cs.. u do lose one stop to 2 stops depending on the magnification power of the T.C used.
 

TMC

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I think he meant that you can still have f2.8 w/o the TC when you dont need the additional range. :bsmilie:
 

lsisaxon

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roti_prata said:
i often use a borrowed nikkor 300/2.8 + tc1.7 when im shooting planes at the airport(past-time)

the benefit of using 180/2.8 + tc1.4 is tt u can hav f2.8 when u need it while the 300/4 is fixed

many of my dawn and night shots were made w/o the tc and then cropped, which proved more effective thn getting blurred pics half the time when at f4
You will get f/2.8 when you take the TC off, with the TC on, the f-number is multiplied accordingly too. ie, 180/2.8 x1.4 -> 252/3.92, 200/2.8 x 1.7 -> 340/4.76.

Take note of the minimum aperture which is still required for AF to work properly. eg Nikon specifies f/5.6, which means that after TC, the max aperture still have to be at least f/5.6 for the AF to work properly.

This is also why one has to be careful when buying 3rd party lenses with varying aperture for Nikon, make sure it is still bigger than f/5.6. So lenses like 18-200/3.5-6.3 are not recommended unless one doesn't mind the hunting at 200mm.
 

roti_prata

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Cheesecake said:
u do lose one stop to 2 stops depending on the magnification power of the T.C used.
embrassed to say:embrass: im not really familar with the stop differences between various f/ numbers

from personal experiences, tc2.0 makes f2.8 f5.6 tc1.7 makes it f4.5 and tc1.4 makes it f4



and i mentioned: w/o tc but cropped is better thn with tc and risking blur pics
 

eawtan

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roti_prata said:
embrassed to say:embrass: im not really familar with the stop differences between various f/ numbers

from personal experiences, tc2.0 makes f2.8 f5.6 tc1.7 makes it f4.5 and tc1.4 makes it f4



and i mentioned: w/o tc but cropped is better thn with tc and risking blur pics
Slight correction - tc17 makes it f4.8
 

lsisaxon

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roti_prata said:
embrassed to say:embrass: im not really familar with the stop differences between various f/ numbers

from personal experiences, tc2.0 makes f2.8 f5.6 tc1.7 makes it f4.5 and tc1.4 makes it f4



and i mentioned: w/o tc but cropped is better thn with tc and risking blur pics
Just need to multiply the f-number by the TC multiplication factor.

The effective aperture of a lens which is the area for light to go through, f-number is related to the diameter of the through which light has to pass through. For long lenses, the f-number can be obtained by dividing the focal length of the lens by the diameter of the front element as the front element is usually the objective, For wide angle lenses, it is not that straightforward.

1 stop of exposure is defined to be a doubling/halfing of exposure time, hence for the amount of light to double or half will depend on the area of the opening. Since f-number related to the diameter while exposure is determined by the area, for the f-number to increase or decrease by 1 stop, it is a multiplication or division by square root of 2 approximately 1.4. Which is why you see aperture like 2, 2.8, 4, 5.6...

1/3 stops and 1/2 stops are more complicated because it involves logarithmic scale. Therefore the factor for these can be obtained by the square root of 2^(1/3) and 2^(1/2) which gives 1.122 and 1.189 respectively. The factor for 2/3 stop can be obtained by sqrt(2^(2/3)) which is 1.259, this can be verified by multiplying the factor for 1/3 stop by itself. Of course you would have to take into account the rounding errors. :) Happy calculating! Hint: You can put the calculations in M$ Excel and you can play with it to gain an insight.
 

lsisaxon

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roti_prata said:
my cam doesnt display f4.8 but f4.5 instead
Are you using a 1.6x instead of a 1.7x? 1.6x 2.8 ~= 4.5.
 

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