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I can't believe I beat Dave in here.
Anyway so I want to speak about some basics and help you decipher what is wrong with a photo.
Photos from these digital cameras are files. In these files there is something called Metadata. "Metadata" is information about the files creation.
This information can be very helpful. It will contain information like the date and time the photo was created, the camera and lens used, many of the settings of the camera and lens like lens Apreture, shutter speed, focal length that particular shot was captured with as well as many other things.
That data is also known as EXIF data. This will help you see what went wrong with the photo. If you are shooting with the D7200 and a 35mm lens it is an effective focal length of the crop factor. It's more like a 50mm lens.
Ok so without explaining crop factor. Let's skip over that and talk about shutter speed. A rule of thumb that makes things easy is you want a shutter speed of 1/focal length when hand holding a camera and shooting a static subject.
That means in your case you need at least 1/50 or faster shutter speed to capture a picture of say an apple sitting on the table.
Moving subjects are a different story. You will need a faster shutter speed to freeze the motion. As stated before there are different types of blur.
Blur type 1. Hand shake
Hand shake from you trying to hold the camera still but you move every so slightly and it creates a blurry photo. That's where the 1/focal length rule applies.
2. Moving subject blur
Kids running around, cars driving etc. You can manage this a couple ways. The easiest and most straight forward is with a faster shutter speed. How fast? Depends on how fast your subject is and how far and what focal length lens you are using.
He other is by using a technique called panning. You pace your subject and match its movement. This has a very cool effect in the photo which blurs the background and keeps the subject mostly in focus. There are caveats but you can look up panning technique for further explaination.
3. Lastly is the Out of Focus area blur.
This is self explanatory but it differs based off the Apreture setting of the lens. It also differs between focal lengths. The more telephoto the thinner the focus plane at a given Apreture compared to a more wide angle lens. The out of focus are helps create isolation for the subject and is best for certain types of photography and frowned upon in certain genres. I won't get into that but this is your basic explaination to help you determine what type of blur you are seeing.
The EXIF data with help you determine it also.
The autofocus systems require a decent contrast to work properly. They also work best in a well lit venue.
By the description you are giving of your subject you may find AF-C your best bet. I don't use he back focus button and I dont teach people to use that method. I had a student that used that method and he had more out of and missed focus shots of anyone I've ever seen in my life. I spent years breaking him of that.
Eventually he gave in and started doing things my way and his photos improved immensely. It may be due to the types of photography we often find ourselves doing but I always use the shutter button to also continuously focus on the subject.
We shoot a lot of automotive static, racing and rolling type stuff.
Sorry this is such a long explaination but I feel it necessary for one to gain an understanding.
Regards,
Mike
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