a question about close up filters...

[saldiamond]

i love how DSLRs have more narrow depths of field, but i can't afford a DSLR at the moment. so i was wondering, if i were to buy a close up filter for my a95, would i be able to have blurred backgrounds if i were to take a picture of something (a person, flower, animal, etc.) far away, or would i have to be close to the subject?

thanks in advance. :)

[JTL]

i love how DSLRs have more narrow depths of field, but i can't afford a DSLR at the moment. so i was wondering, if i were to buy a close up filter for my a95, would i be able to have blurred backgrounds if i were to take a picture of something (a person, flower, animal, etc.) far away, or would i have to be close to the subject?

thanks in advance. :)With a close-up lens, you need to be close to the subject...how close is determined by the focal length, but you will always be operating at the minimum focusing distance for a particular focal length. So, to make it easy for yourself, take the minimum focusing distance for your camera/lens at full wide angle or full tele and divide by 2 for a +2 close-up lens (such as the Canon 500D) and by 4 for a +4 close-up lens (such as the Canon 250D) to calculate the focusing distance with the close-up lens attached.

To achieve shallower depth of field, what you actually need to do is shoot at as wide an aperture as possible. The larger the aperture (smaller number) the less depth of field. Also, shooting at telephoto focal lengths or using a tele-converter will help...the greater the focal length, the shallower "perceived" depth of field (but not actual depth of field). Another trick is to make sure there is distance between your subject and the background.

Here's a blurred background example of something that was about 30 feet away. I shot it with a Canon S2 at f/4 at 400mm:

http://JTL.smugmug.com/photos/43338635-M.jpg

Also, here's some reading to start you off:

http://www.photoxels.com/tutorial_dof.html

Once you get more familiar with the subject, here's some more advanced reading for you:

http://www.luminous-landscape.com/tutorials/understanding-series/dof.shtml

http://www.luminous-landscape.com/tutorials/dof2.shtml

And last, but not least, get out and shoot and experiment! :)

[saldiamond]

thanks so much!

but i just want to make sure i understood your response...

so it's not really possible to get a shallow DOF if i'm far away with a close up filter, and if i had more zoom on my camera, i'd be able to achieve this?

and when i divide my camera's minimum focusing distance by the magnification of the close up filter, will the distance be in millimeters?

also, do natural density filters actually make a more shallow DOF?

[JTL]

thanks so much!

but i just want to make sure i understood your response...

so it's not really possible to get a shallow DOF if i'm far away with a close up filter, and if i had more zoom on my camera, i'd be able to achieve this?

and when i divide my camera's minimum focusing distance by the magnification of the close up filter, will the distance be in millimeters?

also, do natural density filters actually make a more shallow DOF?All a close-up lens does is decrease the minimum focusing distance. Although, to be honest, I never experimented using one for objects far away or at wide angle settings...I have to try that for curiosity sake, but...I'm assuming that a close-up lens should have no effect at infinity...except to degrade the image...but I don't know for sure. Does anyone else have an opinion or fact to offer?

So, let's use your A95 as a practical example. The minimum focusing distance is 18". Put on a Canon 500D and it's 9". Put on a Canon 250D and it's 4.5". It's really that simple. And, millimeters, inches, whatever...half is half, one fourth is one fourth ...;). It's also good to keep in mind...the closer you get to the subject, the narrower the zone of focus/shallower the DOF...

Now, all a neutral density filter does is decrease the amount of light entering your camera. It, in-and-of-itself, has no affect on DOF...but...and it's a big but...because it decreases the amount of light entering your camera, if you kept a constant shutter speed, the ND filter would force you to use a wider aperture to achieve the same exposure. So it could be used as a tool to achieve a desired (in this case, shallower) DOF depnding on your desired exposure. But, people usually use them for the opposite reason, to be able to use a constant aperture yet force slower shutter speeds to achieve motion effects...like those pictures you see of waterfalls where the water looks feathery and blurred. Or it's used when there's just too much light to set the exposure settings the way the photographer wants them. I carry 1, 2, and 3 stop filters with me in my bag...because, hey, you never know!

As far as zoom goes, it has no actual affect on DOF...telephoto focal lengths only create the illusion of shallower DOF.

Remember, DOF is only affected by two things really and a third thing through perception:

1. Aperture
2. Distance to the subject
3. Focal Length (but not really)

I know this stuff can be confusing. But read and experiment. The best way to learn is by doing! :)