Depth Of Field?? (1 Viewer)

[jekatz]

What is more likely to limit the depth of field in my shots, my Zeiss 85 or my Sony W5 at ~f3.4? I find my setup takes fantastic shots of small birds, like the sparrow at

http://www.birdforum.net/showthread.php?t=50955

larger birds, however, are more difficult- most often, the breast feathers are sharp but the head and tail are slightly out of focus. Tomorrow I will post a Coopers hawk to illustrate my problem.

do other Zeiss users find this to be true with other cameras? do other Sony W5 users find this to be true with other scopes? does f3.5 on a sony yield the same DOF as f3.5 on a nikon?

This may be a matter of my technique too-- I shoot mostly at 1.5x zoom on the camera (yielding f3.5) and 20x on the scope. I usually use P mode (the closest thing to aperture priority on this camera), ISO 100, EV 0 or -0.3, no saturation or sharpness enhancement, fine compression, and center auto focus with center metering.

Thanks,
jon

 

[iporali]

What is more likely to limit the depth of field in my shots, my Zeiss 85 or my Sony W5 at ~f3.4?

Jon,

It is more than likely that the limiting factor is high magnification of your scope. Compact digicams are known to have almost infinite depth of field due to their small sensors and short focal length objectives. You can marginally increase depth of field by stopping down the camera, but it often causes more harm by adding blur from motion and shake.

All the scopes having the same power have the same dof, but in theory the cameras may be slightly different (smaller sensor -> more dof).

Best regards,

Ilkka

 

[mmdnje]

Hi Jon and Ilkka: I have attached a composed pic of the same subjetc increasing the F number. Obviously this resulted in slower shutter speed but some of the backgroung becomes more "in focus". The branches are about 1.5m behind the flower and the flower is ~15m from the scope. This was taken using a pentaxPF80A/PentaxXW20mm eyepiece and a coolpix 4500.

 

[iporali]

Jose,

Thanks for a nice illustration of aperture vs. depth of field - and shutter speed. This series of images tells more than 4000 words :t:. I was wondering whether your adapter would permit any fine tuning of the distance between your camera and the eyepiece - that increased vignetting at small apertures indicates that the exit and entrance pupils don't quite match - but are very close.

Ilkka

 

[mmdnje]

The distance between eyepiece and camera is constant. I screw the CP4500 to the eyepiece using a 28-43mm sep ring.

 

[jekatz]

Yes, thank you Jose, that is a good array you posted. I see the background does get a little bit more focused, but there is little effect on the primary subject. I wonder if maybe the autofucus on my camera is slightly off and may be placing the primary subject at the back of the depth of field? I decided that I don't have a great example of this, but this Mockingbird shows it a bit. I am looking at the upper breast feathers, they seem to be in fair focus while the feathers near the back of the head are already out of the field, yet they are only 1 cm, maybe 2 behind the breast.

It is f3.5, shutter 1/500. maybe the foliage confused the autofocus.

thank you both,
Jon

 

[digitalbirdy]

Hi jekatz - really lovely photo that one.
is your softening neck feathers down to depth of focus or movement?
1/500 sounds fast but since I have been digiscoping (only 3 moths) I have noticed that birds can twitch real fast at times!
What makes me wonder about possible head movement is that some of the feathers towards the tail still seem to be pretty sharp - as well as we can see on the smallish image posted.

Regarding Depth of Focus - its a very complex subject. I have been reading a lot on it lately - but some of the explanations were very deep! So I asked for simple answers on the DPreview forum, and got some great and understandable answers.

Here is a link to that thread, I think you may find it interesting:
http://forums.dpreview.com/forums/readflat.asp?forum=1018&thread=17491591

 

[jekatz]

Thanks for directing me to that thread Adrian, you got some good answers to some good questions. I will have to spend some time playing with the calculators, but they have already enlightened me substantially-- I now see that when shooting at just over 1100mm of 35mm equivalent magnification my effective f stop is 2.8, not the 3.5 that the camera shows. I also see what you are saying regarding shutter speed, I could only begin to make inferences about DOF if I was closer to 1/1000, where my Sony W5 tops out.

Thanks again,
Jon