Have I got this right? Canon 1.6 body and 2x extender...

[scotthayes]

I've just bought a Canon 70-200 f/4 L lens.

As my Canon 400d is not full frame I multiply the length of the lens by 1.6 so at 200 on the lens I'm really getting around 320mm.

If I bought a 2x extender and attached the lens to that, would it be 400mmx1.6 thus giving me an effective 640mm lens.

 

[JNB]

Yup, that's it. Focal length x crop factor (x extender multiplier) = effective focal length.

The 2.0x is generally not as well received or reviewed as the 1.4x, however, and decidedly more expensive. I have the 70-400 f/4 L as well, and went with the 1.4x. Couldn't be happier. Gives an effective range of 157-448mm.

 

[compuwar]

I've just bought a Canon 70-200 f/4 L lens.

As my Canon 400d is not full frame I multiply the length of the lens by 1.6 so at 200 on the lens I'm really getting around 320mm.

If I bought a 2x extender and attached the lens to that, would it be 400mmx1.6 thus giving me an effective 640mm lens.

Just remember that you're basically changing the angle of view to an equivalent of the longer focal length on a bigger sensor- you're not changing the actual focal length. The 1.6x is a crop factor, not a magnification factor.

Also, 2x TCs (which is a magnification factor) mostly suck IQ-wise *and* you'll lose 2 stops of light, in the case of an f/4 lens, most likely killing the ability to autofocus since the maximum aperture becomes f/8.

 

[Grimace]

Go with the 1.4x -- there is a serious degradation in quality with the 2.0x.

As said before, the extenders multiply -- the crop sensor zeroes in a the middle part of the shot, it doesn't magnify. It may look that way when printed because you cut out the rest of the image, but you aren't actually getting any closer.

 

[scotthayes]

so with a 400d a 200mm lens does not become a 320mm lens, it's just the area you capture is the same as a 320mm lens?

 

[compuwar]

so with a 400d a 200mm lens does not become a 320mm lens, it's just the area you capture is the same as a 320mm lens?

Exactly. You do get a slight benefit in resolution because you're generally comparing more pixels in the same area that you'd crop unless you're comparing to a much higher-resolution body, so it's not all a loss, but it's not magic either.

 

[scotthayes]

Makes sense now, guy in the camera shop said it in away that made it sound that 1.6 factor of the body changed the focal length of a lens.

Think my best option is to stick with the lens and just get closer to the subject until I can afford the Canon 100-400 L lens.

 

[Grimace]

I'd take the 1.4x + 70-200mm ANY DAY over a 100-400. The former is much much sharper and the 1.4x doesn't degrade the image.

 

[Abstract]

Makes sense now, guy in the camera shop said it in away that made it sound that 1.6 factor of the body changed the focal length of a lens.

Think my best option is to stick with the lens and just get closer to the subject until I can afford the Canon 100-400 L lens.

If you really think about it, why would you care what the crop factor is? You don't need to, and you shouldn't need to. You only need to use the crop factor if you're comparing the "reach" (viewing angle) of your lens the reach you'd get with a 35 mm film SLR, or a full frame DSLR (and there are very few of those), it's not necessary to think of your 200 mm lens as equivalent to a 320 mm lens! However, if you had a full frame DSLR (D3, 1ds series), and another DSLR (eg: 400D), then you'd have to think about such things.

On my D300, I know what my lens will give me using my 24-70 mm. I have a feel for focal lengths on my camera. I know how far my lens would reach if I shot at 70 mm, and I know how wide my other lens will shoot if I set it to 12 mm. You just get a feel for it, and that's all you need to worry about for your own needs. I'm a Nikon DSLR shooter, and that's it. I don't care if the crop factor on a Canon is a bit different, or that a Sigma's crop factor is even more different.

 

[-hh]

I'd take the 1.4x + 70-200mm ANY DAY over a 100-400. The former is much much sharper and the 1.4x doesn't degrade the image.

This is what I did, although I did it with the f/2.8 IS version of the 70-200.

There's a "400 vs 400" review out there (dpreview?) that showed that the 2x isn't the equal of the 100-400, but the 1.4x does appear to edge it out, and you get 3/4's of the way with this combination.

Other factors that I considered...

- combination yields f/4 at 280mm, whereas the 100-400 is probably f/5.6 by this point, so its a faster lens combination.

- one can take the 1.4x off and pick up another stop (f/2.8 to 200mm)

And this one was an interesting comment I came across; still not sure of its a real concern, or all that significant:

- the 100-400 is a push-pull zoom design, which must allow air to get inside the lens someplace, and which can introduce dust.

FWIW, when I was deciding, it was both my first dSLR, and my first ever safari to Africa, where 'dust' has been a huge topic. This was also in the mid/late 2005 timeframe, which was in the earlier days of the digital sensor cleaning learning curve...some of the urban legends back then were that a single particle of dust was horrific and if it got within 300ft of you gear, the sensor's electrostatics would "suck it in" to ruin your day


In hindsight, I still don't know if "pump action" zooms are dust nightmares or not, but I have seen that the Canon EF 100-400 IS is not an uncommon lens selection for Safaris. Thus said, with my current configuration, I believe that I'm close enough to not really need to pick up a 100-400 now, and that my next likely step would be something in the 400mm to 500mm range and probably also complementary to stacking a 1.4x on it as well.

FWIW, one wildlife photographer whose gear selections I'm paying attention to is Art Wolfe. He has a TV program on Public Television that does a nice job of illustrating both the destination as well as giving you insight into how he photographs it ... and even the Videographer does a nice job!


Here's the gear list that Art carries; note that he's using Full Frame dSLRs:

Canon EOS 1Ds Mark II body
Canon EOS 5D body
Canon 16-35mm f/2.8L USM lens
Canon 24-70mm f/2.8L USM lens
Canon 70-200mm f/2.8L IS USM lens
Canon TS-E 90mm f/2.8 Tilt-Shift lens
Canon 400mm f/4 DO IS USM lens
Galen Rowell graduated neutral density filters
Lexar Pro 80x and 133x 4GB CF cards
Gitzo 1348 Carbon Fiber Tripod with the Arca Swiss Ballhead
(12) 60 – 120GB USB 2.0 external drives

-hh