infrared focussing: i am about to put an infrared film in my eos 1. i know the part of focus first without filter and then adjust to the infrared mark on the lens., my question is that...

corryhully Loc: liverpool uk

i am about to put an infrared film in my eos 1. i know the part of focus first without filter and then adjust to the infrared mark on the lens., my question is that as the eos 1 can autofocus through a hoya 720 filter do i thereby not need to adjust. expensive film you see. thanks

Jolly Roger Loc: Dorset. UK

This is a stab in the dark.
Can't you manually focus with the filter off, then carefully fit the filter without disturbing your settings?

Sorry, I have just re-read your question.

TucsonCoyote Loc: Tucson AZ

Nothing is clear in the OP.....just so you know IR focus is slightly off.....older lenses used to have a white dot on them to indicate where to shift focus to!
Edit....I see you know about the dot.....just use it !

corryhully Loc: liverpool uk

TucsonCoyote wrote:

Nothing is clear in the OP.....just so you know IR focus is slightly off.....older lenses used to have a white dot on them to indicate where to shift focus to!
Edit....I see you know about the dot.....just use it !

what is unclear? If you dont know the answer You dont have to comment.

JohnSwanda Loc: San Francisco

TucsonCoyote wrote:

Nothing is clear in the OP.....just so you know IR focus is slightly off.....older lenses used to have a white dot on them to indicate where to shift focus to!
Edit....I see you know about the dot.....just use it !

It isn't just old lenses which have the IR focus shift dot. It's zoom lenses which don't have them, since it would be different at different focal lengths. I have some newer prime lenses which have it.

TucsonCoyote Loc: Tucson AZ

corryhully wrote:

what is unclear? If you dont know the answer You dont have to comment.

I don't see how putting a filter on is going to change anything in the focusing !

BHC Loc: Strawberry Valley, JF, USA

TucsonCoyote wrote:

I don't see how putting a filter on is going to change anything in the focusing !

It has to do with the fact that you are now focusing light of a significantly different wave length. Each wave length focuses differently, but the width of the visible portion of the spectrum is so narrow, we can't see the differences. Move to a different section of the spectrum and there is a slight variation.

TucsonCoyote Loc: Tucson AZ

Mogul wrote:

It has to do with the fact that you are now focusing light of a significantly different wave length. Each wave length focuses differently, but the width of the visible portion of the spectrum is so narrow, we can't see the differences. Move to a different section of the spectrum and there is a slight variation.

Good discussion point if auto-focus took all that into consideration ......but it doesn't work that way !
Most cameras use a passive/split image type comparison to achieve focus.
The more filters and crap you put between the camera and the object to be focused on just obscures the camera's ability to focus at all.

BHC Loc: Strawberry Valley, JF, USA

TucsonCoyote wrote:

Good discussion point if auto-focus took all that into consideration ......but it doesn't work that way !
Most cameras use a passive/split image type comparison to achieve focus.
The more filters and crap you put between the camera and the object to be focused on just obscures the camera's ability to focus at all.

Sorry, I wouldn't know. All my IR pictures were manually (actually zone) focused. There's not a lot of visible light to see to focus; I'm surprised a camera can auto-focus with an IR filter attached.

jerryc41 Loc: Catskill Mts of NY

corryhully wrote:

i am about to put an infrared film in my eos 1. i know the part of focus first without filter and then adjust to the infrared mark on the lens., my question is that as the eos 1 can autofocus through a hoya 720 filter do i thereby not need to adjust. expensive film you see. thanks

Lots of info here. If you like shooting IR, have a camera converted by LifePixel or another company. You can also buy them on ebay.

http://photography.tutsplus.com/tutorials/an-in-depth-guide-to-infrared-photography-setup-and-capture--photo-9533

BHC Loc: Strawberry Valley, JF, USA

jerryc41 wrote:

Lots of info here. If you like shooting IR, have a camera converted by LifePixel or another company. You can also buy them on ebay.

http://photography.tutsplus.com/tutorials/an-in-depth-guide-to-infrared-photography-setup-and-capture--photo-9533

Test the camera first; not all cameras have a filter on them. It's really easy.

TucsonCoyote Loc: Tucson AZ

JohnSwanda wrote:

It isn't just old lenses which have the IR focus shift dot. It's zoom lenses which don't have them, since it would be different at different focal lengths. I have some newer prime lenses which have it.

That's odd ....my AF Nikkor 70-210mm 1:4 has the IR focus shift mark ! :XD:

BobHartung Loc: Bettendorf, IA

corryhully wrote:

i am about to put an infrared film in my eos 1. i know the part of focus first without filter and then adjust to the infrared mark on the lens., my question is that as the eos 1 can autofocus through a hoya 720 filter do i thereby not need to adjust. expensive film you see. thanks

Autofocus is set for visible no infrared light. Autofocus only works with digital cameras when you focus in live view.

corryhully Loc: liverpool uk

BobHartung wrote:

Autofocus is set for visible no infrared light. Autofocus only works with digital cameras when you focus in live view.

That is what I was thinking bob , but my camera autofocuses with the ir filter on. i am guessing that enough visible light passes through the 720 filter for the eos 1 to focus.