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For sports, I know that a faster lens would usually be considered more important than image stabilization, but what if, after selecting your shutter speed, your camera is picking apertures that don't require a super-fast lens?

Here's my specific example: I bought a Sigma 70-200mm F2.8 lens for my D90 thinking that I would need the F2.8 in order to shoot at my daughter's Figure Skating club. I chose the Sigma over the Nikon 80-200mm F2.8 because the Sigma had full-time manual-focus and a built in auto-focus motor and was about $100 less expensive. The Nikon 70-200mm F2.8 with VR was well beyond my budget.

Now, having used the Sigma a few times, I am pretty happy with the shots I am getting. I set the camera for a shutter speed of 1/500s and ISO-800 and let the camera pick the aperture. However, it turns out that most of the shots I am taking end up with the camera choosing an aperture of F4 to F5.6 (the lighting in the rink must be better than I thought).

So, my question is, would I be better off returning the Sigma 70-200mm, and getting the much less expensive Nikon 70-300mm with VR (saving almost $500 that I could put into another lens or a tripod). The aperture range of 4.5-5.6 on the 70-300m is around what I am shooting at, plus the lens has VR (I know it doesn't help with moving subjects, but I am shooting hand held at 1/500s for the moment).

I could even bump the ISO up to 1600 to maintain or increase the shutter speed with the 70-300mm. On the other hand, in a different arena, the lighting might not be as good, and I'll be wishing I still had the F2.8.

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All good answers, each adding useful information: some cameras have special AF sensors at F2.8, AF will be faster at F2.8 because of more light reaching the sensor, rule of thumb for shutter speed as inverse of focal length for when VR becomes useful, possibility of sharper images from faster lens when stopped down. How do I just pick one answer as "the correct one"? –  seanmc Oct 27 '10 at 2:39

6 Answers 6

up vote 9 down vote accepted

Generally good advice with regard to IS and it's ability to freeze action. However I'm surprised no-one has mentioned the fact that some camera bodies have extra sensitive AF points that are only active with f/2.8 lenses. Thus if you have an f/2.8 lens, even if you end up shooting at f/4 or f/5.6 you are gaining an advantage from the max aperture in terms of focussing performance. This is why f/2.8 is the holy grail of sports lenses, it's not for the speed, it's the for the AF.

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do you know if the Nikon D90 one of those bodies? –  seanmc Oct 23 '10 at 23:34
    
The specs state it has a central cross type sensor (i.e. sensitive to horizontal and vertical contrast), however I can't find anything that says it's only active at f/2.8 and faster. However faster lenses are generally better for AF, and will give you a brighter viewfinder image (until you dip below f/2.8) due to the fact the lens remains wide open until you fire the shutter. –  Matt Grum Oct 24 '10 at 11:03

I have a Canon 70-200mm f/2.8 L IS USM, and I do shoot sports now and then (roller derby for example, since we are talking skating). This is a great lens, sharp even at f/2.8, and I like to shoot at that aperture because of that great, creamy bokeh. Provided that the light is more or less constant at the venue, I shoot in Tv mode (shutter speed priority) and make sure the shutter speed is fast enough that the camera will pick f/2.8. I double-check now and then because if the light decreases, my 5DMII would start increasing the ISO, and I'd rather avoid too much noise. If you can, why not even go full manual: pick f/2.8, ISO 800, and just do a few test shots to see which shutter speed provides the correct exposure. Not always do-able outdoor, but a bit easier indoor with constant light.

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Two things need to be considered here: focusing speed and adequate sensitivity to light to achieve a fast shutter speed.

Zoom lenses are much slower than prime lenses in the same grade because they have lots of moving parts internally. Also, lenses with smaller maximum apertures (like 4.5) are going to be slower to focus because less light gets to the camera (which does all the real focusing magic).

VR/IS does nothing for action shots. It really only accounts for slight movement of the camera when shooting a still scene at a slow shutter speed. It can actually be detrimental when paired with a tripod, and it'll just suck down battery unnecessarily with a fast shutter speed.

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Stabilization is primarily intended to help when your shutter speed is less than the reciprocal of your focal length. Even taking crop factor into account, 1/500 on a 300mm lens shouldn't require vibration reduction since a 300mm lens would want a 1/300 or 1/450 shutter speed as a base for handheld (though my personal experience indicates you don't need to consider crop factor, other opinions vary). Net effect, getting a 70-300 will give you greater range for the action, but I doubt the VR option will end up mattering all that much.

Now, as mentioned in a way, what you may give up is a sweet spot at a wider aperture. Faster lenses often, though this isn't hard and fast, will have a sweet spot at a larger aperture than a slower lens. So what may result is that, by switching, you lose a little sharpness at f4.5 or 5.6. That's not assured, but something to consider.

If possible, before making such a switch, I would see if you can rent the lens and try it out. If you're happy with the outcome, make the switch, the extra 100mm can come in handy. However, if you find the sharpness and quality is missing as a result, then you're only out the rental cost.

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The most important fact - which is buried in one of the previous responses - is focus speed. DSLR Cameras always focus at their widest aperture. So even if you are taking a shot at F/5.6, a lens that can do F/2.8 will let much more light in during focusing.

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Often a faster lens will be sharper even at the same aperture as a cheaper lens. It's not universally true, but it's true often enough that you need to take it into consideration.

I'm not familiar with the Nikon lens you're considering, but it's almost certainly smaller and lighter than the Sigma.

You're the only one who can weigh the plusses and minusses in the end. If it were cut and dry, one or the other lens wouldn't be on the market.

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