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Near out-of-focus point, program to determine

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#151 MartinPond

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Posted 03 June 2021 - 05:43 PM

Please, spell out "depth of field" or "depth of focus", as the case may be, instead of the acronym DOF.  They are closely related but distinct optical terms.  In some of the posts in this thread it is difficult to tell from context which one the acronym was intended to stand for.

Yes, thanks....good chance to make it clear.

 

Depth of focus is 100.00% of what I am talking about since  post#1

 

NOT Depth of field.

 

 

JG: they bleeped out your respectfull obscenity,

       but 41.9uM out of a 200mm FL is amazingly tiny.   

       And seeing the difference between 2000m  and 750m with a 7x50 is unrealistic....

      It's a bit frightening you don't have a feel for that.

 

And, a reminder:   Depth of focus 



#152 KBHornblower

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Posted 03 June 2021 - 08:20 PM

Check out this reference, along with others that can be found easily enough.

 

https://photographyl...-depth-of-field

 

In addressing the distance to the objects as in your opening post and beyond, it is consistent with the photographic presentation above to call it depth of field.



#153 MartinPond

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Posted 03 June 2021 - 08:39 PM

Check out this reference, along with others that can be found easily enough.

 

https://photographyl...-depth-of-field

 

In addressing the distance to the objects as in your opening post and beyond, it is consistent with the photographic presentation above to call it depth of field.

In photography, depth of field is depth of focus.

I like that, but everything is prime focus...

 

In microscopy, it gets more complicated.



#154 KBHornblower

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Posted 03 June 2021 - 09:38 PM

In photography, depth of field is depth of focus.

I like that, but everything is prime focus...

 

In microscopy, it gets more complicated.

Check out this one.

 

https://www.mastercl...-depth-of-focus

 

Scroll down to Depth of Focus vs Depth of Field.  The author explains the distinction between the two closely related but distinct optical topics.  What applies to cameras also applies to telescopes.


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#155 MartinPond

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Posted 03 June 2021 - 09:56 PM

Check out this one.

 

https://www.mastercl...-depth-of-focus

 

Scroll down to Depth of Focus vs Depth of Field.  The author explains the distinction between the two closely related but distinct optical topics.  What applies to cameras also applies to telescopes.

Another article + POV.

I do like this better.   They are differently figured for the two.



#156 MartinPond

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Posted 03 June 2021 - 10:18 PM

OK:

   From what JG used, I can see what happened.

By going through the objective and eyepiece, I figure the location

   of the virtaul image...

 

 

USAGE:  finalfoc  FLobj(mm)  FLep(mm) Dtarg(meters)

 

D:\all_prog\tcc\tcc-0.9.26-win64-bin\tcc>finalfoc 200  28.6  750

 

fl_obj:200.00 fl_ep: 28.60  Dtarget: 750000.00  Image is at: 15304.88
 

You final virtual image is at 15304mm, JG , or  15meters.

You said that you just need glasses for under 2 meters....farsighted.

 

I'm certain you could see a sign very

   sharply at 15meters ..<----the place where the 750m target makes its image.

 

 

So...you have a near-focus limit on your eyes of 2m , or 2000mm.. (w/no glasses on)..

 

let's do some iterations to find out what you near-focus outside distance should be:

fl_obj:200.00 fl_ep: 28.60  Dtarget: 60000.00  Image is at: 1194.24

fl_obj:200.00 fl_ep: 28.60  Dtarget: 70000.00  Image is at: 1398.76

fl_obj:200.00 fl_ep: 28.60  Dtarget: 80000.00  Image is at: 1603.24

 

fl_obj:200.00

fl_ep: 28.60 

Dtarget: 100000.00  (100m)

     Image is at: 2012.21

                                  <--farther to target than most people,

                                      but it should look just sharp enough at 100+ meters to target.

 

I am discovering both correction and acomodation matter,

   but looking  at the final virtual image location makes it easier....it puts the final image

     into a space I can understand from an eyeball POV.  1,2meters....10,100, etc.. 


Edited by MartinPond, 03 June 2021 - 10:37 PM.

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