how is this so shallow?

wiganwez

wiganwez

Suspended / Banned
Messages
426
Name
Wez
Edit My Images
Yes
just been looking at this picture

http://www.flickr.com/photos/joecroos/861507909/

here is the data for it

Camera: Canon EOS 350D
Lens: Tamron SP AF 28-75mm F/2.8 XR Di LD
ISO: 100
Focal length: 75 mm
Aperture: F/2.8
Exposure time: 1/200 sec



my question is i have a 50 mm f1.8 and wide open with my lens i get no where near as shallow dof as the above image. is it because he is at 75mm?

maybe a noob question but all credit to the photographer it is a great image

thanks
 
aperture and distance from the subject affect the DoF - I think this pic was taken close with a 75MM lens at f/2.8 - but your right - a great shot. :)
 
Last edited:
mostly because the background is just further away probably. the focal length of 75mm at 2.8 on the 350d crop does give a shallower dof than yours wide open but try it with a far away bg and you'll get the same effect
 
wiganwez said:
cheers fr that from ding the calculations of the two lenses you can see the tamron would have much shallower dof. cool site
Click to expand...

Not necessarily. It's a question of magnification (focal length x distance) but if you move close enough with your 50 to fill the frame with that subject to the same size, you would get the same DoF aperture for aperture. At f/1.8, you would obviously get quite a bit less than f/2.8.

Check on DoFmaster. It's easier to do the sums if you compare 50mm and then 100mm at twice the distance - DoF will be the same.
 
You can focus quite close to the subject with the 50mm f1.8, so get as close as you can to the subject, and make sure that the background is far enough away to give a nice smooth effect.

Steve
 
Don't forget as well that at 75mm your camera (not full frame camera) adds a magnification factor of 1.5 so your lens is actually shooting at approx 110mm, hence the reduced dof.
 
khitomer said:
Don't forget as well that at 75mm your camera (not full frame camera) adds a magnification factor of 1.5 so your lens is actually shooting at approx 110mm, hence the reduced dof.
Click to expand...

That's no true. The depth of field at 75mm remains near-enough the same regardless of the sensor size.

There is no "magnification factor".. you're just seeing a smaller area of the image projected by the lens. The field of view changes, but nothing else.
 
Alastair said:
That's no true. The depth of field at 75mm remains near-enough the same regardless of the sensor size.

There is no "magnification factor".. you're just seeing a smaller area of the image projected by the lens. The field of view changes, but nothing else.
Click to expand...

That's not true either. There is a magnification factor when you change format, because the sensor size is different and the field of view changes (by the crop factor) and depth of field changes with it (also by the crop factor).

If you have a 50mm lens on a crop format (Nikon 1.5x) camera, from the same shooting position your framing will be identical to using full frame with a 75mm lens, but the DoF will be greater by just over one stop.

For example, f/4 on the cropper is the same as f/6 on full frame (f/number x 1.5).

Edit: check it here http://www.dofmaster.com/dofjs.html
 
Last edited:
.
 
Last edited:
You must log in or register to reply here.
Back
Top