What make and model camera? Which Sigma lens? Do you have autofocus turned on, both on the camera and the lens?
Testimonial: "Wow, that would be helpful! I have a Canon Rebel t3i and a Sigma 70-300mm F/4.0-5.6 DG AF"
SOURCE: Using auto focus 35-55 mm lens on d40x will not
It is because the lense is only an AF lense. The d40x doesn't have an on-body auto focus motor so that needs to be on the lense. I have a d60 and have the same problems. You can use the manual focus on the AF lenses; however, to use auto focus, you need to buy an AF-S lense. It's disappointing I know, but that's the price we must pay for saving on our body lol
SOURCE: My Nikkor AF-S DX VR 18-200 stopped focusing
the lens internally has a electrical circuit ribbon that contracts when you adjust the lens everytime. They are prone to get crease causing a short in the auto mode.b It can be checked and replaced bt most camera technicians
SOURCE: I have a weird problem. When i put the 50mm 1.8
You probably have a problem with the A/M switch on the body-- flipping that switch should extend or contract the autofocus pin that drives the lens. This particular lens doesn't have its own focus motor, so there's no way that it could be focusing on its own without the pin from the body driving it.
Try taking the lens off of the camera and looking at the autofocus pin as you flip the switch from auto to manual focus.
SOURCE: I accidently knocked over my
The impact damage to the lens will require complete disassembly to repair. These are quite complicated but can be repaired fairly inexpensively. However, it's not a user serviceable problem and will need to be repaired by a qualified service technician.
My name is Rick and I'm a professional repair technician with over 20 years in the business and have repaired many of these. I'm semi retired and work from home with little overhead so I can keep repair costs low. If you decide to have the camera repaired, please click HERE for a directory listing that suits your needs. If this response has been of any help to you, please be sure and give a positive vote for me on FixYa.com.
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Canon Rebel t3i with a Sigma 70-300mm F/4.0-5.6 DG AF
Do you have autofocus turn on, both on the camera body and the lens?
Yes. My Canon 18-55mm focuses fine.
The camera thinks that it has successfully focused, but it's just a blur.
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