dsjtecserv

dsjtecserv

Lives in United States Northern, VA, United States
Works as a Technical Director
Joined on Jan 21, 2005

dsjtecserv's recent activity

  • Yes, it isn't really important that the people be the same ACTUAL size as the moon! ;-) First, to even come close to having the moon fill the frame, you would need a very long focal length. The ...
  • Haha, no argument. You were fine in your original post, but went down the wrong trail in your follow-up. So yeah, assuming its "easy" to maintain the same framing, you'll get shallower depth of ...
  • No, I think that's not what you meant! I think you meant for the same framing of the scene (and same f-number), the depth of field will be shallower on full frame than on crop. To maintain the same ...
  • I use the 58 mm 500D on the 70-200 F/4 IS, and a step down ring without any problem; no vignetting, on a crop-sensor camera. I can't recall whether I have used this on full frame, so I won't ...
  • Gentlemen, focusing is done with the lens wide open. It doesn't matter what f-number will be used once the aperture is stopped down and the picture taken. If the lenses on either format have the...

  • Gentlemen, focusing is done with the lens wide open. It doesn't matter what f-number will be used once the aperture is stopped down and the picture taken. If the lenses on either format have the...

  • Replied in Compression
    You are forgetting that the degree of enlargement and assumed viewing distance are also factors in depth of field. Until the image recorded by the sensor is enlarged to a viewable dimension, depth ...
  • Replied in Compression
    Yes, of course, because you then know the magnification desired. Thank you for making the connection for me. Dave
  • Replied in Compression
    Good point. Although to determine scene width, you would need to know something about how far away you want to measure the width, which brings us back to needing to know the subject distance! Dave
  • Replied in Compression
    And enlargement from the size of the recording medium to the final assumed viewing size. That is the source of the circle of confusion, which is also an element of the equations used to calculated ...
  • Replied in Compression
    A simpler way of understanding the relationship between focal length and subject distance is to keep in mind that depth of field is a function of magnification, and that magnification in turn is a ...
  • Interesting that exactly the same issue came up in the Open forum at almost the same time. As others have said above, the perspective relationships among objects ("compression") is a function only ...
  • Replied in Compression
    That's generally a nicely done and succinct explanation. As Mr. BG says, it is a frequent source of confusion, and this is a good reference to strainten that out. There was one area that is ...
  • For your situation, pay attention to jetals' answer; thats the right one. What you are experiencing is not due to a temperature difference between the camera and the air, but simply because the air ...
  • Replied in Scheimpflug
    Focus stacking is a valuable tool (I use it a lot), but it doesn't emulate the effect of tilting the lens relative to the image plane. With focus stacking, the plane of optimum focus stays ...
  • Well it would apply any time the lens is stopped down, for whatever reason. A more common situation is a variable aperture zoom lens, when the maximum aperture at the longest focal length is ...
  • Exactly! You said it perfectly. Yes, this is also true, except that depth of field would in fact be different, unless you took steps to equalize that as well. The image shot with the 24 mm lens at ...
  • Yes. One will be more tightly framed than the other. But for all of the objects that are contained in both, their relative sizes and positions will be identical. You could, in fact, take the more ...
  • You are misunderstanding. A lens' focal length doesn't change depending on the sensor it is used with. That is correct and not in dispute. But you are incorrectly assuming that perspective is a ...
  • I think you are mixing two effects. I have no problem autofocusing even through 5 stops of ND when the ambient light is bright, even though my f/4 lens is effectively f/22 by your logic. That is ...
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