I have tested a +6 Macro lens with M67 thread and found that I can see the edge of the lens in the image when I take pictures without zoom. I need to zoom in on the image to get the desired effect. Of course I see the great advantage of the lens, but I originally learned to shoot macro completely without using the zoom. Is this a common “problem” with which you have also experienced or is it normal?
Answer by PanOceanPhoto
Don’t worry, zooming in is no problem, quite the opposite!
The statement that you should not “zoom” underwater (regardless of macro or wide angle) comes from the fact that you always want to have as little water as possible between the subject and the lens.
Now it’s like this: When you zoom in, i. e. choose a higher focal length, you seem to bring the subject closer to your camera and it will appear larger on your picture. The real distance and the path of light through the water remains the same. You will find that you can’t even get closer to your photo motif. Because with a higher focal length, there is always an extended close-up limit. In other words, your subject will no longer be in focus after a certain distance.
Unless you’re using a lens. This looks like a magnifying glass. On the one hand, it enlarges the subject (= higher magnification). However, it also reduces the close-up adjustment limit. That means you can get closer and your camera can still focus clearly. Of course, with the attachment lens you can keep it that way: With a longer focal length, you (theoretically) always have an enlarged close-up limit. But we are only talking about a few millimetres to centimetres. And for animals with flight behaviour you are happy if you can stay 2 cm further away. As long as you don’t have to keep even more distance to the subject, everything is fine.
And one last thing: you could also think about an achromatic. These lenses are magnifying lenses that are designed to reduce chromatic aberrations. And in most cases they also have less edge blurriness.