Re: Depth of field difference between APS-C and full frame

cmyk wrote:
Paul Furman wrote
cmyk wrote:
Paul Furman wrote

I like the visualization idea but I can't really follow it without a drawing. I would plug it into that calculator but I'm not sure how to figure the field of view at different focal lengths and focal distances. That calculator does include focal distance and there is a drawing but I don't know how the light bends to reproduce the drawing for these scenarios:
http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

If someone can tell me what focal distances will fit a face at 50mm on full frame and 50mm on APS, we can run the numbers and have an answer.

If we assume that adult faces are roughly 30*20cm, you could position the 50mm lens on the 35mm SLR at a distance of 50cm from the subject. This would give a FoV of 36*24cm. Using the same focal length on a Canon (FoV 1.6 crop), Nikon (1.5 FoV crop), APS-C (1.44 FoV crop) DSLR, you'd get the same FoV at 80cm, 75cm and 71.8cm, respectively.

What distance using 50mm on a 1.5 crop?

75cm - as stated. Oh, and I assumed the shots would be portrait.

Ah, OK sorry... brain freeze... the answer according to that calculator is the cropped DSLR has deeper DOF than the full frame 35mm camera with the same 50mm lens even if you step back to get the same magnification of the face.

at 50mm f/1.8 focused at 0.2 meters on full frame
0.5m Closest distance of acceptable sharpness
0.5m Furthest distance of acceptable sharpness
0.01m Total Depth of Field

at 50mm f/1.8 focused at 0.75 meters
0.7m Closest distance of acceptable sharpness
0.8m Furthest distance of acceptable sharpness
0.02m Total Depth of Field

However.... it's still possible (likely?) that since the OOF background is now enlarged due to a longer effective focal length and the associated compressed perspective, then the OOF background is enlarged enough to make up for that difference.

Say the background is a point of light at 1m distance... the OOF circle is whatever it calculates at... use a longer effective focal length and the background OOF circle gets bigger, therefore more out of focus, less acceptably sharp.

--
Paul Furman Photography
http://edgehill.net
Bay Natives Nursery
http://www.baynatives.com
.

Relevant Pages

  • How can I check if a shape overlaps a hidden geometry section?
    ... with a rectangular geometry section to define the scale ... and starting distance of each section of the drawing. ... Way hidden so as not to clutter the drawing. ...
    (microsoft.public.visio.developer.vba)
  • Re: Hubble deep field question
    ... Let's check that with Ned Wright's cosmology calculator: ... and the next line of the output gives the angular scale ... An interesting property of the angular size distance is that it ...
    (sci.astro)
  • Re: Hubble deep field question
    ... Let's check that with Ned Wright's cosmology calculator: ... and the next line of the output gives the angular scale ... An interesting property of the angular size distance is that it ...
    (sci.astro)
  • Re: Measuring Tool
    ... No need to create a drawing to measure distance. ... absolute space to absolute space, ... reference from, so I need a nearest point. ...
    (comp.cad.solidworks)
  • Re: Flight Planning for Long Trips
    ... I programmed a HP 27S calculator for GC navigation. ... CG distance in SM and NM, I input an estimated ground speed ... courses since the program measures courses east and west of ... | flights most GA aircraft are capable of making. ...
    (rec.aviation.piloting)