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06-22-2020, 09:59 AM   #1
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Do any 645 macro lenses report magnification ratio?

I have 645 A 120 macro. It doesn’t even report focal length ( miss that "extra" feature from SR on ibis Pentax ). The FA 120 and 90 macros supply focal length info but do they specify the magnification the lens was at?

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barondla

06-22-2020, 10:41 AM - 1 Like   #2
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QuoteOriginally posted by barondla Quote
The FA 120 and 90 macros supply focal length info but do they specify the magnification the lens was at?
The larger question might be whether the camera EXIF supports reporting magnification. ExifTool's Pentax support is pretty exhaustive, but magnification is not there.

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An option might be to manually determine by direct observation at various focus distances.


Steve
06-22-2020, 11:35 AM - 1 Like   #3
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It is interesting that the sigma 70 macro lens has markings on the lens to tell you. As the lens extends the mark shows on the barrel. Isn't this focal distance the info needed for ttl? It should be able to record this.
06-22-2020, 03:39 PM - 1 Like   #4
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QuoteOriginally posted by swanlefitte Quote
Isn't this focal distance the info needed for ttl? It should be able to record this.
Rough distance information is available, but the magnification markings on the lens are not reported to the camera or if they are, it is something that has not been figured out by the good folk at ExifTool.

What is provided are are one of eight different integers tagged as FocusRangeIndex by ExifTool, that give a rough estimate of distance. Four have been given labels; they run as follows:
  • 0 (very close)
  • 1 (close)
  • 2
  • 3
  • 4
  • 5
  • 6 (far)
  • 7 (very far)
Of course, this information is provided by AF lenses only, but usually continues to work even when using manual focus. I just took a series of test shots with my Sigma 50/2.8 EX DG Macro at several magnifications and got these results:
  • 1:1 - very close
  • 1:1.2 - very close
  • 1:1.5 - very close
  • 1:2 - very close
  • 1:3 - very close
  • 1:5 - close
  • 1' - 5
  • 5' - very far
The information is pretty "course" and may vary by lens. For example, my FA 35/2.0 returns the following:
  • 1' - very close
  • 1.5' - very close
  • 2' - very close
  • 3' - close
  • 7' - 4
My Sigma 17-70/2.8-4.0 (C) is the same as the FA 35mm except for "3" at 7'.

Whether P-TTL flash uses this or some other measure is not known, but FocusRangeIndex is the closest thing to a distance measure yet found in the Pentax EXIF.


Steve


Last edited by stevebrot; 06-22-2020 at 04:39 PM.
06-22-2020, 06:41 PM - 1 Like   #5
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QuoteOriginally posted by stevebrot Quote
Rough distance information is available, but the magnification markings on the lens are not reported to the camera or if they are, it is something that has not been figured out by the good folk at ExifTool.


Steve
It is cool you tested it. Unfortunately it isn't very helpful. I wonder if it is based on full rotations of some mechanical part (screw) of some part as it focuses.
06-22-2020, 08:22 PM - 1 Like   #6
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QuoteOriginally posted by swanlefitte Quote
It is cool you tested it. Unfortunately it isn't very helpful. I wonder if it is based on full rotations of some mechanical part (screw) of some part as it focuses.
My understanding is that the encoding is passive and read in a manner similar to the mount contacts. Turn the focus ring and the pattern of exposed contacts changes.


Steve
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