Digital Zoom Discrepancy Between Tutorials

John, question about some images in the Digital Zoom Tutorial compared to images found in the PTZ Guide (Both excellent references, by the way) In the first you make a strong case for the irrelevancy of higher than single digit zoom factors. As an extreme example you show this highly pixelated crop and zoom (12X) of a 29MP image:

Then in the PTZ guide, while making a similar if less vitriolic point, you max out the digital zoom here to 12X on a 2.1MP camera:

To my eye, the first one is far more pixelated and has been zoomed far beyond the point of being helpful. The second picture on the other hand, while no Van Gogh, is just reaching the point of not being helpful, IMHO.

Yet, the first is from a 29M image and the second from a 2.1M image, one with less than 1/10 the pixels... How can it be?

Note: The quality difference seems so large that I assume I am misunderstanding something from the videos, or my math is wrong. That's ok by me. Also, I apologize if my cropping and sizing for the post has altered the perception of the images, I don't think it has; but use them only as a reference back to the actual videos to be safe.

I do, of course, have a theory that might explain it partially but first I want to make sure that I have the comparison framed correctly. Thanks!

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*** ** **** ** **** (*** ****), *** ***** ** a ***. *** **** ****** ******* **** ****** ***** ** different.

*** ** **** ** **** (*** ****), *** ***** ** a ***.

* ******* *** '*****' *** ** ****in *** ****** not the VMS, and yes it can matter.

*** **** ****** ******* **** ****** ***** ** *********.

** ****'* *** ** ** * ************* ********* **** ***** than *** ****' ***, *** **** ***** *** **** ***** help **? ******'* ** ** **** ******** *** ****** ****** *** *** ******* *** ******* ************** **** *********** **** * ***** * ********** **** **** like?

*** ** *** ***** **** ** *** **** ** ** reporting ********* **** ******, ******; ******* ***** ** * ****** but ********************** ********* **** ******-**** ******* **** ********** *** ****-******** ******* *****, ******* ** *** *** ** gimp.

****** ******-**** **** *** (*** ****** **) ****before *** ***********/******** is performed, otherwise *** *** **** ********* *********. Though not noticeable at low zooms, once you get to the point where 9x9 macroblocks are identifiable the difference becomes apparent.

* ***** **** ** *** ****** **** *** ***-*********** **** 12X **** ***** ******* **** *** ****-*********** ******** ***.

**** ***** ********** ** ****: ******** *** ****** **** *** do *** ******* **** ***** ** **** ** ** **** as ******, **** **** *** **** *** **** *********** *****. If ** *** **** ********* *** ***-************* ***** *** *** ****, *** **** ***'*.

** ***'* **** ****** ** ********* ** ** ***** *** far *** ******* **** ****** **** *** *******. *** *** low *** *** ***** ** ******* ***, *** *** **** and *** *** ****** **** *******. * **** ********* *** would **** ** **************, ***** ** **** ******* ** *** camera. ** ****** **** ** *** ****** *** ****. ******-*** cameras, **** *** *** ** *** *****, **** *** * selectable ***, *** ****** ****, *** ****** ** ***** ***** you **** *** ******** ** ******.

***'** ***********.

**** ** **** **** *******.

***, ***** *** ***** *** ** ** ******** **** ****, so ** *** *** ***** ** ** ******** ***** ***, but ** *** **** **** **** ******* ** *****, *'** be ***** ** ****** ****.

***'** ***********...

*** *** **. **** ** ** *****, * ** *** speculating

  • **** *** **** ***'* ******* **** ** **** ** *** camera, *** *** ***
  • **** *** **** ***'* ******* **** ** **** ****** ***********
  • **** * ****** ******* ***** ** ******** ** ******* ****** compression
  • **** * ************* ******* **** **** **** * **** ** impact ** *** ********

** *** ******** **** *** ** *****, * *** ******* reasonable ********.

* ** *********** **** *** **** **** **** *** ****** after *********** *** ** * ********** ***** ****** (** ****** zoom ******) **** ** *** ******* ******** ******.I *** ** *****.

**'* **** **** * **** ******** *** ********* ******* ** two ********* ******* ** *** ********* *****, ** ****? ** it ****** *******? ** ***** **** ** ****** ** *** Axis, ***** ** ** *** *** ***** **********, *** ******* camera ****** ***** ***** ****** *** ********. *** *** **'* image ***** *** ******. **'* * ******* ******** ** *** happen ** ***** *** ****** **** ** ****.

******, * *** *** ***** **** *** ***** *'* **** 'busting *****' ** *********. *'* ***. * *** ****** ****** to **** ***** *** ** **; *** ********** ** *** result * **** ******* ***** **** ****** ****** *****... ** for *****, *** ** *** **** * *** **... ***** Alex *. *** * **** ** *** ******* ****** **** he *** **** *** ** *** *** ******* ****/**** ****** access/corridor **** ;)

"**'* **** **** * **** ******** *** ********* ******* ** two ********* ******* ** *** ********* *****, ** ****? ** it ****** *******?"

******* **** **** **** ** ********* *********, **** ********* ****** sizes, **** ********* ***** ******* ******* *** ** ********* ************. For *******, *** **** *** *** ***** ** * **** smaller ***** **** *** ******** ***, ** ***** ***** (***** is ****** ****** ** **** **** * ******* ** *** Exacq ******).

****'* ******* **** ****** ****** ** ** ********* **** ****'*. For *******, *** ** **** ** * **** ***** ***** in * *** ******* / ******* **** *** ** **** HD. ** *** ***'* *******, *** *** *** *** **** yourself *** *** **** *** ****.

** *** **** ** ** * **** ***** *** **** methodology *** **** *******, **** ** **. ***'* ********* *** draw *********** ***** ******* **** **** **** ***** ********* ******.

*** **** ***** *** ** ****, *** *********** ***** *******, claims ** ******* **** ** *** **** * ******** ********** as *** ******* *** ** ********* ****** *** *** ** their ***** *** **** **** ****** ** **** *** ********** details ** *** ***** / *****.

"******'* ** ** **** ******** *** ****** ****** *** *** ******* *** ******* ************** **** *********** **** * ***** * ********** **** **** like?"

***, *** *** ********* **************************** * ***** ***** **** ** *** ** *** ***** to ******* *** ******* *** *** *********.

*** *******, *** **** *** *** ***** ** * **** smaller ***** **** *** ******** ***.

***** **** *** *** ** ******? ;)

***, * **** **'* *******, * ******** *** ** ********* zoom ** * *** **** ** ********* ** **** *** Gimp ***, **** **** ******* ********* *** **** ***.

*********** ** **** ** **** *** ** *********** ********** ***** we **** **** **** ******** ***:

****'* ******* **** ****** ****** ** ** ********* **** ****'*. For *******, *** ** **** ** * **** ***** ***** in *lot ******* / tighter than 12x on Axis HD.

***** ** ***, ** ** ********.And ** * *****, the Gimp image appears zoomed in far more That could certainly be what I subconsciously picked-up on and good reason for the quality difference. That ***** ******* ** and I would be ready to accept it, case closed, if it weren't for this baffling (to me) picture:

****'* *** *****, ** ************ ******* **** ****** *************** ******why ** ***** ******** *****? Not only are they apparently between two different cameras mfrs. Axis and (Canon?*), but they also show that Axis' digital zoom is reported in line with the way their optical zoom is. ** **** **** ********* **** ******* **** ** ** *** think **** ******* ******* **** *********** **** **?

*** *** ** ***** ** *** ***** **** "*** ****** has **** **** ****** ******* ****", *** *** **** ******* multiply **** ** ** **** **** ******, **** *** *****-********* cameras. *** ** *** *** ***** ***** *** **** ********* differences, **** **** ***** *** ***** ** ***** ** **** cameras, (*** ******* *** **** ****** ***** *** ** *********).

** *** **** ** ***********,*****'* ************* **** ***** ***** *** ******* ***** ***** **** ** the **** ***** **** *** ***** *** ****?? (* ****, I ****, *'* ******** * ***** ***** ***. ;)

******** ** ** *****.

"****'* *** *****, ** ************ ******* **** ****** *************** ****** *** ** ***** ******** *****?"

* ** ****** **** ******* **** ****** *** ********* **** gimp, *** ********* **** *****.

***, ** ******* *** ******, *** * ** **** *** agree, **** ******* ** ***** ******** ** *** *** ****. Clearly, *** ***** ** ****** ** *** ***** ** *** better, ******* *** ***** ** ******* **** **** *******.

**********, **** * ** ****** ** **** **** ***** ******* zoom ** * ***, *** *** ***** ** **** **** than ****** ** '**' ********** ** **** *** ****** ****'* its ******* **** ***** **.

* ** ****** **** ******* **** ****** *** ********* **** gimp, *** ********* **** *****.

**. ******* ***** ****** **** *** ****** **********'* ******** ******* zoom **** **** ********** ******* ***** *******? ****/***** ** ****?

*******: ***** ********* *** ***** ********** ** *** ** ** and **** ******** *** *-**** *** ** ** *** ** 48 ****, * ******* **** ***** *** **** ************ ****** the ***** ** *** *****. **** ************ *** ***** ******* as *** ** ** *** ** **. **** ***** *** entire ***** ****** *** ***** ******* ***** ****. *** * do ********* *****? *******'* *** ***** *** ****** ****** ** the *** *********?

******* *****=*.*

**. * ******* ** ***, ** ***********.

PTZ ******** ** ****.

*** **** ****** ****, **** ******* *** *******, **** *** PTZ ********do ******** ***** ****. I scaled in gimp the wide opening Axis shot to 40x and then to 120x and the FOV's match up.

*** ****** **** *** ******* **** ******** ******** **** *** more **********, **** ****** ****** **** ****** ********** ******* ** simple:

*** *** (*********) **** ******* * ******** ** *** ****** zoomed *** ** **** *******. **** ** ******** ******* ********* and ********* *********,*** ****** * *** ******,gimp ***** *** ***** ***** ****** ****** **** ***** ****. But as you point out, you don't have a 3MP screen, so when you zoom much of the scene goes off the screen. Especially in the case of the 12X 29MP image. Which gives the illusion of extreme zooming. So you were right in saying that the two screenshots can't be compared, but the reason is that one is not displaying the whole zoomed FOV.

***** *** ***** **** **** ** **** ** ********* ** atechnical *****, at least?

* ******* *** *****, ***** * ******* **'* ******* ** you ***** *** *****, ** * ****'* ******* *** *********** or '********'. **** ****** ** **** ***** *** ****. *** I ** **** ****, *** **** ******* **** ** **** not ***** *********.

****, * ****** *** *** ******** ** ***** **** ** doesn't ****** ******* *** ***** *** ** *******, *** ***** I ****** ** **** **** ** *** ********* ***** **** technically ** ********.