depth of field on digital w/telephoto lens...

[Andrew OShea]

does anyone have experience using a telephoto lense on a camera like the pdx10 (whixch I have)... Im wondering what effect it has on the depth of field if any, being that digital is so flat??? Thanks...

[Boyd Ostroff]

Hi Andrew, and welcome to DVinfo! I'm moving your post to our PDX-10 forum. Actually, digital isn't flat; it's totally related to the size of the camera's imaging chips and on the PDX-10 that is very small. For a technical discussion, read the following article: http://www.dvinfo.net/articles/optics/dofskinny.php

If you zoom all the way in with your PDX-10 you will decrease the depth of field, and if you add a telephoto adaptor you will further reduce it. However this may not be very practical in all situations since you'll have to get really far away from your subject.

I have the Sony high grade 2x telephoto for the PDX-10, and it's a very nice lens. However I'm not sure you're barking up the right tree if your goal is just reducing depth of field. Why not just zoom in all the way with the built-in lens?

You should also shoot in full manual mode and open the iris all the way. In bright conditions you might want to use a screw-in neutral density filter to help with this.

[Andrew OShea]

i want to incease the depth of field not reduce it, zooming in all the way would increase it, zooming out all the way or using a wide angle lens would decrease it.....

[Andrew OShea]

do i have this backward??

[Boyd Ostroff]

Originally Posted by Andrew OShea

do i have this backward??

I have no idea.... INCREASING the depth of field means that objects which are both near and far away will be in focus at the same time. The small chips on a camera like the PDX-10 make this pretty easy. Using the wide end of the zoom increases depth of field. You can shoot with a small f-stop to increase even more.

DECREASING depth of field means that near objects would be in focus and the background out of focus. To do this you need to shoot with the widest f-stop and also zoom in. Cameras with larger chips (like 2/3" video cameras or 35mm film cameras) have LESS depth of field than small video cameras.

Which do you want?

[Andrew OShea]

i want to decrease the depth of field, (its been a while since I picked up a camera or learned about depth of field) its confusing anyway... I want to try whatever I can to achieve a filmic quality regarding subjects being in focus in the foreground and out of focus in the background... With DV (espeacially lower end cameras) its hard to achieve this without zooming to a super close up... I just want to know is there any way to achieve that using the pdx10, is there any kind of lens attachment that will help that? Im shooting my thesis filmand I cant afford to shoot film (not to mention i didnt pay much attention in film class, young and stupid) and i want to just get the best possible results from this camera since thats what im using period. If you have any more info or advice id appreciate it... Thanks....

[Boyd Ostroff]

Originally Posted by Andrew OShea

With DV (espeacially lower end cameras) its hard to achieve this without zooming to a super close up... .

Please read my earlier post again, and read the article in the link I posted above if you really want to understand depth of field. It has nothing to do with "lower end cameras." It has to do with the size of the camera's CCD's. Small CCD's result in lots of DOF. Zooming in is the only way to really accomplish what you want. Adding the telephoto adaptor will have the same effect as zooming with the built-in lens.

If this is something important for you then you may want to consider one of the 35mm adaptors people are discussing in our Alternative Imaging forum: http://www.dvinfo.net/conf/forumdisplay.php?f=70 These use 35mm lenses which focus an image on a piece of ground glass which your video camera records. There are a variety of other issues associated with them however.