Can anyone help? I am using a nikon d7000 for sports photography. My husband kindly bought me a sigma 70-200mm telephoto lens 2.8 as I shoot a lot of low light indoor sports. I have only just started testing it but I am finding that it will not focus in some low light situations. I am keen to know what the best settings to use would be for low light indoor sports. I often get a blur with my 3.5 lens.
Indoor sports photography is a big challenge. You're going to have to be shooting wide open likely in high ISO ranges. If you can set up a remote flash somewhere to pick the scene up a couple stops you'll likely be better off.
I've got a Canon 70-200 f/2.8 and it was really tough to stop the motion (~1/500-1/1000) even at the high school level without getting up to 1600 ISO.
Well, the three values that matter are aperture, shutter speed, and ISO. All of these are in your control, but only if you know what they do for you. I apologize if you know all this, but others may ask the same question, so...
Aperture - This is the ratio of the focal length of the lens to the diameter of its opening. The smaller the aperture number, the bigger the opening, the bigger the opening, the more light it gathers for any given shutter speed. However, typically the more wide open a lens is, the less sharp it is, there's a "sweet" spot that varies a little by lens and sensor size. In any case, in very low light, you're going to want to be wide open or very close to it.
Shutter Speed - Well, this obvious, but it's important to note that when you do not control the light, then the shutter speed is what freezes motion. So, depending on the sport, you're probably going to be anywhere from 1/500s and above to freeze motion.
ISO - The sensitivity to light of the sensor. Low ISO is less sensitive, but usually much less noisy. High ISO is much more sensitive, but also noisy. Nevertheless, in a low light situation, even with the lens wide open, the ISO is going to be at the high side. The good news is that the D7000 is very strong at high ISO, you can get very nice images at 6400 and not bad at 12,800 with a little work.
So, as to specific recommendations... I would shoot using shutter priority or, more preferrably manual with auto ISO enabled. Ideally, I would want to control my aperture and shutter speed and let the camera pick the ISO if the light tends to change a bit (you do have a camera that gives you a lot of latitude in ISO). If the light is constant, I might go fully manual and set all three values, it just depends.
Autofocus on a camera requires enough light for the electronics to pick out distinct edges in the subject.
In daylight it's pretty easy because the changes from shadows to lit areas, or patterns in clothing, or the difference in tone between the subject and the background, help the camera.
It's easy to test how the camera determines how to focus by trying to focus on a monochromatic surface, i.e., one that has no changes in color. A smooth blank white wall can make a camera nuts because, if there are no changes or edges or shadows, it can't latch onto anything and will just seek a focal point then give up.
Similarly, when the light levels drop it gets hard for the camera to find the edges, because the contrast has dropped too. New cameras use more sensitive sensors to pick up focus, but still, they get fooled once the light gets too low. At that point you can try to help the camera out:
- Add a bit of artificial light. Some Nikon flashes will turn on a red beam in a vertical pattern, which helps the camera find the edges. Other cameras can turn on a white LED that adds a bit of light, helping it find the edges.
- Use a small flashlight to illuminate the subject quickly, for the above reasons. A red filter over the bulb might help protect your night vision, be less distraction to others, or might even make the subject stand out to the camera better - I doubt the focus sensor is color, so red might give it better black and white contrast to work from.
- Focus on something that is well lit and the same distance from the camera as the subject then recompose your shot with the subject without refocusing.
- Focus manually.
The f2.8 lens gives you two extra stops of light when focusing, compared to a normal consumer lens which is f5.6. The aperture you have selected for the exposure won't matter when focusing because the camera has the aperture wide open until the shutter is released. At that point the aperture is stopped down, the shutter opens, the picture is exposed, the shutter closes, and the aperture opens to full again. You can prove this is what happens by setting a slow exposure, looking into the lens, releasing the shutter, and watching the blades of the lens close down. Once the shutter closes, the blades will reopen to the full aperture of the lens. If you have a depth-of-field preview button, you can press it while looking down the lens barrel and see the same thing occur. The camera does this so the full amount of light is getting down the barrel while you're setting up the shot and focusing.
I have shot a lot of fast action in lousy light, and acquiring and maintaining focus can be a real problem. I'm using a Canon f2.8 70-200 also, and had to figure out how to quickly find something on the subject that would help the camera acquire and track focus. Once I had focus I could fire, and my strobe system would provide enough light for the right exposure. There were plenty of "hail Mary" shots, where I hoped it had focus because I could barely see - I'd prefocus then wait for the subject to get to that distance then fire, which is an old trick from the days of manual focus. At least the exposures looked good because of the strobes though often the action looked horrible.
It's a tough trade-off and the best answer is to practice with the camera in similar situations so you have your bag of tricks ready when you encounter similar problems while shooting for real.
Sigma 70-200mm is very inconsistent in the AutoFocus department and well known for major focus problems. Life is good when it focuses right, but a sharp lens will not delivery sharp images if not focused properly. You might consider getting another copy of the lens. If possible, get Nikon 70-200 f/2.8 which is more likely to solve your problem. Just so you know, its okay for your camera to hunt a little bit in low light conditions unless you buy a top end piece of optics. In this case, bumping up ISO seems to be the best option for you.
EDIT: Bumping up ISO solely isn't gonna solve the issue, bumping up the ISO gives you chance to use smaller aperture and most lenses perform better when stepped down. I personally never used the Sigma 70-200mm but when my lens starts hunting, I generally bump the ISO up and use a smaller aperture, this solves the issue most of the case.
Thanks to rfusca for pointing it out.
I have been setting the camera to manual exposure with f/4 and shutter 1/1250 and auto ISO on the basis of getting best aperture/shutter combination and the camera setting ISO as the cameras now have higher ISO settings.
I have been pleased with JPEGs which were strong and sharp.
I have tried aperture priority with fixed ISO but get exposure problems when sun pops out or those dark clouds appear.
Make sure you are using Continuous Servo AF, which is displayed as AF-C. That means it is continually focusing on a moving subject, instead of focusing once then waiting for you to take the photo. With AF-C, the D7000 will determine what the subject is, focus on it, and keep it in focus as it moves. This is especially important in sports photography where your subject is moving around alot.