How to shoot through curved glass

[sphelps]

Originally Posted by MarkoD

Why would it be hard to get anything sharp? I use a 70-200 f2.8 on my tank all the time

Same reason why macro lenses are prime. With a fixed focal length a prime lens can be designed to better reduce distortion and typically have better optical quality. For the most part the wider the zoom the more distortion you get resulting in a softer image. Not always an issue but trying to use a zoom lens in a macro type environment doesn't always work well, combine that with curved glass and you're really in trouble. Just something to keep in mind if you're trying to reduce one issue you may be introducing another one.

Now with that said one can't compare the 70-300 with the 70-200 you have, those are much different when it comes to optical quality and design, hence the price difference.