Back Focus

[antdickens 0]

Could someone please explain back focus for me. What happens if you don't do it and what do you gain by doing it?

 

Do i need to buy a neutral density filter?

 

 

So confusing

[AVCONSULTING 0]

Back focus may or may not be needed and is usually employed when using zoom lenses so that the focus is good from very wide angle to telephoto. Sometimes on a fixed focal length lens you need to backfocus if the lens won't focus using the lens' own focusing knob.

 

Using neutral density filters when focusing is necessary if you are using an auto iris lens. Because depth of field varies depending on the amount of light you can have a very good focus during the day and find out that at night you have a blurry picture. What you need to do is fool the lens into thinking it is night time and then focus. This will prevent problems later.

[rory 0]

Back focus may or may not be needed and is usually employed when using zoom lenses so that the focus is good from very wide angle to telephoto. Sometimes on a fixed focal length lens you need to backfocus if the lens won't focus using the lens' own focusing knob.

 

Using neutral density filters when focusing is necessary if you are using an auto iris lens. Because depth of field varies depending on the amount of light you can have a very good focus during the day and find out that at night you have a blurry picture. What you need to do is fool the lens into thinking it is night time and then focus. This will prevent problems later.

 

or just focus it in dim lighting. Also, I always backfocus for the final focus, this way its guarenteed to be as crisp as possible, though you can get away without it, and even without focusing in dim lighting or with filters, depending on the camera.