Sigma 70-200mm f2.8 APO DG HSM Image Quality Issue

Question

I have a question regarding the quality of my Sigma 70-200mm f2.8 (non-Sport) lens. I bought this lens back in 2011, and even though people say again and again a 70-200mm is a must-have, this is my least used lens. I photograph mainly sports and wildlife, and I mostly avoid this lens. At wide apertures, I know that the DOF is very narrow; however just about everything in any image I shoot with this lens at any aperture wider than f/8 is blurry and/or out of focus.

I took a couple of test shots at f/2.8 and here they are (unedited). Both images were shot at ISO 250 at f/2.8 and a shutter speed of 1/4000.

In the image of the solo athlete, the focus was on the athlete's jersey; however only the "Rocky - 21" graphics and her v-collar are sharp, not even her face is. If you look by the soccer ball and really on the entire left half of the image, there seems to be a radial blur around the athlete. I am well aware of bokeh at wide apertures for objects that are not in-focus, but this looks like motion blur moving circularly throughout the left half of the image.

The second image of a larger group is similar. I will say, though, that this shot was unplanned, in that there is no true subject, as I just fired the shutter without thinking. There is an athlete, that just happened to be in focus here – the girl in the way back to the right of the girl with the pink headband.

I have seen plenty of f/2.8 sports shots where, yes the background is out of focus, but the entire athlete is sharp as a knife. Has anyone else experienced this with their lenses? Is it an elements issue. I agree, this is an older lens, but I had this issue even when I bought it. I have another Sigma telephoto lens that performs similarly at wider apertures. So all of my sports photos (at least daytime) are shot at f/9 or tighter because that will produce sharp images. I have been critiqued with the fact that a narrow aperture will create a busy photo because you can see more of the background, which is true, but otherwise none of my images will be sharp. It might be hard to tell because of the compression requirements for this forum.

Thank you all very much for taking the time to read this. I hope I did a good job at explaining this because I stumped the employee at my local photography store. If this is something that happens naturally, just tell me bluntly haha. I have never worked with Canon or Nikon glass, so I figured it was a third-party thing, but I am totally stumped.

[EDIT]: As comparison, I found this blog entry from Rick May. If you scroll down a bit on the page, he has a sample image with his 70-200mm 2.8. link: https://alphauniverse.com/stories/what-s-in-my-bag--how-a-sports-pro-built-an-ultimate-sony-lens-kit-for-fast-action/

For these images of mine (and others I have taken under these conditions- not provided), it looks like, to me anyway, someone has taken their hand and smeared it across and smudged the image.

Answer 1

To be honest the images look to be about fine in my opinion. I dont know what level of quality you want to achieve but if your goal would be to capture the action at a sport event those images look as they were delivering.

If there is any back or front focus you could get your camera lens combo calibrated.

Personal stuff:

I also owned that lens and shot it multiple years on a 12 MP fullframe Nikon D3. I quite liked the lens. When I stepped up to the D5 with 20 MP I often find the images at 2.8 too soft and shot mostly at F/4. A few years later I upgraded that lens with the Tamron G2 one which is a heck a lot sharper at 2.8, focuses faster and feels more solid in my hands. I recently stepped up to a 45 MP D850 with a 400mm F/2.8 lens and I redefined sharpness wide open at F/2.8 so I stop down my newer 70-200mm too. You cant say a lens is good or bad. You always need to say a lens is good or bad compared to what.

But as I said in the beginning: The images look just fine too me. Also you cropped a good amount to the images and it always depends on what you want to achieve. Those images certainly get the job done. If you dont like the quality as your needs get higher over time you might want to upgrade the lens.

Gear does matter but a great image is a great image because it is a great image. Not because it has the most megapixels or is taken with the greatest lens.

Answer 2

The lens is only half the equation when shooting sports at wide apertures. The camera body's AF system also plays a huge role. So does the way the camera and lens interact.

In both of your images something is in focus, just not necessarily what you intended. So the lens is capable of reasonably sharp photos. You've just got to learn how to tell it where you want it to focus.

Part of the issue could be inconsistency on the part of the camera's AF system. The original Canon EOS 7D, for example, was notorious for just missing focus in about equal amounts both in front of and behind the subject when using AI Servo AF in continuous drive (burst) mode. Mine certainly fit this description, and it forced me to learn the ins and outs of its AF system so I could at least get the most it was capable of when using it. Once I moved on to other Canon cameras with more consistent AF, understanding how to tell the camera where to focus where I wanted it to focus instead of letting it focus where it wanted to focus was invaluable.

It's also possible that the lens doesn't always set focus at the exact distance the camera told it to. A few years ago Roger Cicala wrote a blog article about how some AF systems are 'open loop' and others are at least 'semi-closed loop'. With open loop systems the camera tells the lens how far to move, assumes the lens has moved that distance while the mirror is flipping up out of the way (and the AF system is then "blind"), and then takes the picture. Closed loop systems have extra sensors in the lens that confirm to the camera body exactly how far the lens actually moved compered to how far the camera told the lens to move. If needed, the camera can then move the lens another incremental amount to get it closer to where it told the lens to move while the mirror is flipping up before the shutter opens. One needs both a camera body and lens that communicate using newer closed loop protocols to get the increased performance.

If the lens seems to always miss by about the same amount in the same direction, using AFMA (Canon), AF Fine Tune (Nikon), or whatever other manufacturers call camera body/lens calibration can be helpful if your camera includes this feature.

Another hardware related issue might be that the camera/lens combo can't move the focus distance fast enough to keep up with the action you're trying to track. Some bodies can move the AF elements of the same lens faster than other bodies can drive that lens. It usually has to do with the amount of battery power available. Top tier pro bodies tend to run at 11 volts (which is the output of three lithium-ion cells), while most other bodies tend to use 7.4 volts (which is the output of two Li-Ion cells per battery).

The other part of this, though, could be user error. The way AF systems works isn't always as intuitive as we think it is . Most of the AF "points" are far larger than the little dots, circles, or squares we see representing them in the viewfinder. Cameras will try to focus the area of greatest contrast within the entire active focus area, not what is exactly underneath that little AF "point" symbol. It takes a little effort to learn what the actual size of the active AF areas is for each "point" for your camera's AF system. Sometimes you can find published diagrams.

Sometimes you have to experiment with your camera to create your own "map", like Andre did in this blog entry.

Understanding what areas are active with each AF "point" will help you to better see what areas the camera "looks" at to find the area of greatest contrast on which to focus.

For a comprehensive look at possible reasons why photos aren't focused sharply on the intended subject, please see How do I diagnose the source of focus problem in a camera?