Why does wide angle lens adapter + large aperture make images blurry?

Question

I have a kit 18-55mm lens on my Canon. I also have a .45 wide-angle lens that I use on the kit lens. The results are fairly sharp.

When I try to use the .45 wide-angle lens on the 50mm @ f/1.4, it produces blurry images. Changing the aperture f/5.6+ on the 50mm, the images become sharper.

The 50mm produces good images, so it's not the 50mm lens. The 18-55mm also produces good images by itself and with the .45, so it's neither the kit lens, nor the .45 wide-angle lens.

Keep in mind that I manually focused, had a tripod, good light, and was shooting still photography.

So, why is this happening? Why can't I use a wide-angle adapter on my 50mm at a large aperture? And why does it make the photo blurry?

Answer 1

All optics has their own disabilities, and the two lenses are so little blurry you cant notice it. Larger apertures gives more blur. The 50 mm lens you cant notice on its own, the wide angle converter adds so little blur that you cant see it on the small apertures, but the blur on F/1.4 multiplied with the blur on the converter is enough to notice it. Does the specs on the converter say something about what aperture range the optics is made for?