My first Bahtinov mask was for the Canon EF 200mm f/2.8L. On the EF 400mm f/5.6L, I had always problems to recognize the typical pattern in LiveView mode (10x). And in the last few months my images were sometimes a little bit out of focus…
So I decided to buy a new Bahtinov mask for the Canon EF 400mm. It’s a Gerd Neumann 77mm Bahtinov mask (77mm lens filter size) made of black coated aluminum.
I’ve to practice only removing it after focusing… If the lens hood is completely moved back, it turns together with the focus ring. So I’ve to be very careful, when I move out the lens hood back after focusing.
This Bahtinov mask has much smaller and much more slots than my first mask. I was able to made a test tonight and it works like expected… YES! 🙂
The pattern is clearly visible at 10x magnificaion in LiveView on my EOS 70Da.
It seems that the typical pattern becomes visible for stars < mag 4, even clearer for stars below mag 3. Also check that the star is not exactly centered on the displays field of view when not magnified. It’s better when the star is in the left or right third. This gives you a better averaged sharpness for the whole image.
Live View EOS 70Da