If it was not ok and caused problems, don't you think these third-party makers would be out of business? That there would be thousands of posts online to bash them? That people on this forum would never recommend them? That a google search for "is it ok to use a third-party lens" would yield thousands of replies?
There is no problem with using 3rd party lenses at all. But let me quote from the digital picture website.
You should be aware that there are potential issues with third party lenses. Since 3rd parties reverse engineers (vs. licenses) manufacturer AF routines, there is always the possibility that a new body might not support an older third party lens. There are examples of this happening in the past. Sometimes a lens can be rechipped to be made compatible, sometimes not. Additionally, there is the risk of a problem that results in the lens and body manufacturers pointing blame at each other.
Third-party lenses have always served me fine... you just have to watch out for some of sigma
's older lenses peeling and the IQ of the lenses. Otherwise, u will be able to get along fine unless u are a pixel peeper.
let me see...Tamron is 3 year warranty, Sigma is 2 year warranty so if i am not wrong...they are very good alternatives to lens manufacturers that offer 1 year warranty especially important if you buy lenses with high speed motor as they can be expensive to fix out of warranty.
One good thing about staying with original manufacturer is that the lenses MTF data can communicate with the camera to put it simply so each lens is optimized somewhat.
Depents on which DSLR body you're using. Generally no problem but not all 3rd party lenses are 100% compatible unless they stated it clearly in the lens specs.
So to play it safe, first read lens specs, read reviews, and read complaints as well!
only if all sound good then ask and compare price from those well known shops. CS also have some guide, make sure you know the range of price and have a benchmark. Don't forget to ask the warranty!
Always bring your camera to the shop and try with different aperture setting and shuttle speed to view the IQ, some even do a focus test as some time lens will have back or front focus problem...
Before you pay them...
3rd party lens can be very good too. Just to give an example: Tamron 28-75mm F2.8. It cost abt SGD580. A similar lens under Sony is Carl Zeis but it cost close to SGD 3000. I read a comparison review on these 2 lens. Although CZ built quality is a lot better, the image quality beats tamron only slightly. Given the big price difference, Tamron is a better deal.
And perhaps you have read something about the QC issue on front/back focus of certain models. It will not cause any problem to your camera except the out of focus image.
For me, you are paying 2~3 times more on a manufacturer's lens for an increment of 20~30% performance. But somehow, some 3rd party lenses had fetched even better reviews as compared to manufacturer's lens.
So now you are safe to use 3rd party lens, happy shooting ~