The phrase "effective focal length" is a standard optical engineering term that (to use a lot of words) refers to the net focal length of a combination of refracting or reflecting surfaces in some particular configuration. I do not know the origin of the term. But yes, it is "just the focal length"...

Robert, why are you calling these focal lengths "effective focal lengths"? Aren't these just the focal lengths, as usually defined, at the various magnification (focus) settings? What is "effective" about them? Sorry if this topic has already been discussed. And thanks for doing these measurements. ...

Does the lever clamp tighten as well as a turning knob? I have never used that type of clamp. It is super tight for the plates I tried, but you are right to be concerned as there is no adjustment. Perhaps some plates will not fit well. It works great for me but is an expensive solution ($120). I tr...

I had this problem and I solved it by using an RRS lever clamp.

This can happen when the point a focal length downstream of the exit principal plane lies within the physical lens. The infinity-focus aperture can assume what seems to be an unphysical value but this is okay as the lens cannot form an image of an object at infinity (the image plane is inside the ph...

Rik, Thanks for responding to my comments and questions. On the first point, I think I did not make myself clear. I think we are in agreement, actually. When I said "Nyquist business," I meant that to include the deconvolution of the binning. That is what is discussed in the article I referenced ear...

In my mind these two uses of "reconstruction" are quite closely related. In both cases we wish to recover some original signal that has been altered and sampled. Whether we call the alteration a point spread function or an impulse response makes little difference to the math necessary to do the rec...

What's bothering me is that in this thread "reconstruction" is used in two unrelated senses. This thread started by discussing reconstruction of the image from Nyquist samples. This somehow evolved into discussions of reconstruction of blurry images using deconvolution or whatever. The first topic r...

Here is how I think about this now. There are only two lengths involved, the object size and the wavelength lambda. To get good resolution, the ratio size/lambda must exceed n, the number of pixels across the field (I am ignoring small numerical factors here). If, in addition, we want good depth of ...

Why do we need to use focus stacking for photographing a bug but not a tiger? Some will say that it's the large magnification required for the bug photo. But suppose the camera is smaller than the bug? Then we are not in the macro regime any longer and all should be good. This is an extreme example ...

mawyatt, I don't know enough about this topic to comment. I found this article by doing a google search on "Nyquist binning" I think. By following the prev and up links I found that this is related to a manual on SPEX, a code for spectral X-ray analysis. The author appears to be Jelle de Plaa. This ...

mawyatt wrote: What first struck me is that I believe the 1st equation 7.1 is incorrect, the Fourier transform equation has omitted the time domain function f(t) within the integral!!

You're right. I noticed that too but then forgot about it so I didn't mention it.

To tie up the loose end concerning sampling vs. binning, I found a relevant article: http://personal.sron.nl/~jellep/spex/manual/manualse95.html . The sampling theorem does apply to binning also. If the original image is bandwidth limited, then the original image can be reconstructed from the bin in...

Rik,
Thanks for helping me understand how binning should be handled. The effect may be small but you did say that the difference between 1 and 1.22 is significant, so maybe small effects make a difference and should be considered.

Sincerely,
Walter

A camera sensor does not really sample the image at a finite number of points. It histograms the image into a finite number of bins. This is not the same thing and I wonder if the sampling theorem even strictly applies to this case.