What is the fisheye effect and how to match with it?
Probably every photographer trying to use wide-angle lenses noticed, that the wider angle objective is, the more distortion it causes on the scene. So what to do about it?
If we speak for most popular 35 mm format, typical fisheye length would be 8-10 mm for circular images and 15-16 mm for full-frame images. One could think, that the more you shrink into a scene, the better, alas, this person soon find out, that with wider focal lengths (24 mm and bellow) start to appear distortions of picture. Every single one objective got it, however in narrower focal lengths it is almost unnoticeable. Nothing in world is perfect, which unluckily count even for photographic lenses too.
Physics laws simply can't be passed, however, there are few great trick, how to overcome this.
First of all, it is not bad idea use fisheye effect to your gain - art shoots, security cameras with 360° cover, meteorology or photographing of clouds or panoramas brings you very distorted picture, however it may be from time to time exactly what you want - unrealistic, but artistic! Fisheye lenses are usually very expensive, so be careful when choosing pricey one. As common shooter you'll probably use it very rarely.
If you want to photograph something like panorama of rising sun, there is no need for fisheye lenses. Today there are available applications, which takes common shoots (even from very narrow lengths like 300 mm) and connect them to one maxi and ultra-wide photo. It is recommended to take such photos from tripod and so, that each one covers also 1/3 of previous, so software has got easier work connecting them. Such applications are able to connect even nets of pictures like 10 x 3 shoots etc.
Third way, how to overcome fisheye effect, is again software, but with a little different application. For example if you want to straighten lines on 18 mm length photo, simply use your favorite software and tell the function, which focal length you used (better applications may be able to read this information directly from JPEG EXIF). Do not forget, that the narrower focal length you use, the less likely this effect appear.