TC + Sigma50-150 = AF ?

[redwine]

Hi,

If i get a Sigma 50-150mm f2.8 + a 1.4x or 2.0x TC on a D90,
Would it AF on my body ?
And what is the max aperture for both TC..... f5.6 ?

Thanks

[wildsoyabean]

it should AF.
on 1.4x ap = 2.8*1.4 = <5.6
on 2x ap = 2.8*2 = 5.6

[redwine]

Originally Posted by wildsoyabean it should AF. on 1.4x ap = 2.8*1.4 = <5.6 on 2x ap = 2.8*2 = 5.6

Thanks,

You mean if its 2x magnification, then its 2 stop slower ?
So if its 1.4x, then its around 1.5 stop slower.

Is there anything to look out for if deciding to get Sigma or other brand of TC ?

[kagaya]

yeah. i also planning to get this for my D90.
is sigma 50-150 a worth to buy lens ?
and it is worth to buy a TC or it's better to get another lens ?

[wildsoyabean]

its not 2 stops, its a multiplcation.
2.8 * 2 =5.6 (for 2x coverter)

2.8 *1.4 = 3.92 (for 1.4 converter)


i never tried a before. ha.
i use 18-270mm ...more than enough for my usual shots.

[derrickbettas]

i have a 1.4. And i used it on my sigma 70-200 , it works perfectly but not on my 150-500. don,t know WHY? Can,t even on MF .Thanks.

[redwine]

Originally Posted by kagaya yeah. i also planning to get this for my D90. is sigma 50-150 a worth to buy lens ? and it is worth to buy a TC or it's better to get another lens ?

I guess it depend on what you want,
I do more on portrait, so on my crop body it give 75-225mm,
while other telelens are 70-200, which i find a bit too tele for body shots.

Other factor is the small size, weight of this lens compared to other f2.8.
In case i need more tele, its good to know i can add a TC later.

[redwine]

Originally Posted by wildsoyabean its not 2 stops, its a multiplcation. 2.8 * 2 =5.6 (for 2x coverter) 2.8 *1.4 = 3.92 (for 1.4 converter) i never tried a before. ha. i use 18-270mm ...more than enough for my usual shots.

Thanks for the clarification.
So with the 1.4TC, i still can get f4 @ 315mm (150 x 1.4TC x 1.5crop)
that's pretty decent.

[redwine]

Originally Posted by derrickbettas i have a 1.4. And i used it on my sigma 70-200 , it works perfectly but not on my 150-500. don,t know WHY? Can,t even on MF .Thanks.

Thanks for sharing,
Looks like its important to get the 'correct' TC.

[kagaya]

Sigma claimed that their 50-150 F2.8 works fine with 1.4x or 2.0x TC
by the way, what is the price of this lens and these TC in the market ?
where can get the cheapest deal ?

[blurblur]

Hi, I brought the len for Sony mount @$1200 at IT fair Sigma booth. Just collect last week still no chance to use yet. But is lighter than i expected as I always think the F2.8 len will be very heavy

[calebk]

Most cameras will still AF with a 2x TC on a f/2.8 lens, because most camera bodies can AF with lenses up to as slow as f/5.6.

[calebk]

Originally Posted by wildsoyabean its not 2 stops, its a multiplcation. 2.8 * 2 =5.6 (for 2x coverter) 2.8 *1.4 = 3.92 (for 1.4 converter) i never tried a before. ha. i use 18-270mm ...more than enough for my usual shots.

AFAIK, the multiplier is the effect on focal length. In terms of light loss, it's one stop for a 1.4x TC, and two stops for a 2x TC. Light loss is not correlated to the converter's multiplier.