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FORUMS Photography Talk by Genre Macro Talk
Thread started 11 Nov 2017 (Saturday) 13:03
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Photographing a moth egg - advice please

 
Trik
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Nov 14, 2017 14:00 |  #31

Archibald wrote in post #18496375 (external link)
Hint - shorter focal length will give more magnification.

So, are you suggesting that my wide-angle at, say 50mm, might be better, or only if reversed, please?

Trik




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Temma
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Nov 14, 2017 14:03 |  #32

Trik wrote in post #18496359 (external link)
I am unsure as to how they work as well - after each movement, I would need to re-focus. Is that correct?

No.

You achieve initial focus slightly in front of the subject. You never touch the lens afterward.
All subsequent focus changes are accomplished by moving the entire camera forward via the rail until you have an area slightly behind the subject in focus.




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Temma
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Nov 14, 2017 14:17 |  #33

Archibald wrote in post #18496375 (external link)
Hint - shorter focal length will give more magnification.

I get my greatest magnification from a 50mm Minolta manual reversed onto two sets of extension tubes.

I've been keeping my eye open for a bargain on another manual lens in something like the 28-35mm range.




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Wilt
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Post has been last edited 3 days ago by Wilt. 4 edits done in total.
Nov 14, 2017 14:20 |  #34

Trik wrote in post #18496381 (external link)
So, are you suggesting that my wide-angle at, say 50mm, might be better, or only if reversed, please?

Trik

extension / FL = reproduction scale...

As already suggested, use the SHORTEST AVAILABLE FL lens with a specific extension tube in order to obtain highest magnification of subject on focal plane

  • 25mm extension on 100mm FL (focused at infinity) = 25/100 = 1/4 scale image
  • 25mm extension on 50mm FL (focused at infinity) = 25/50 = 1/2 scale image
  • 25mm extension on 25mm FL (focused at infinity) = 25/25 = 1/1 scale image


...of course, the above does not take into consideration the internal focus mechanism's own Minimum Focus Distance (using no extension tube).

Consider how long of an extension tube is needed, to obtain a 1:1

  • 100mm extension on 100mm FL (focused at infinity) = 100/100 = 1/1 scale image at a distance of 400mm from subject to focal plane (4* true FL)
  • 50mm extension on 50mm FL (focused at infinity) = 50/50 = 1/1 scale image at a distance of 200mm from subject to focal plane (4* true FL)
  • 25mm extension on 25mm FL (focused at infinity) = 25/25 = 1/1 scale imag eat a distance of 100mm from subject to focal plane (4* true FL)


BTW, 50mm is NOT 'wide angle' especially on your APS-C frame size 7D or 7DII ! 50mm FL does not become 'wide angle' unitl it is mounted on a medium format camera like a 645 or 6x6 format.

And reversing any lens on a dSLR makes for very inconvenient macro shooting of any live mobile subject because of the methodology needed to shoot with any lens -- particularly for any lens which ordinarily uses electrical contacts to communicate with the body! It is workable (but nevertheless rather awkward) even with a moth egg (which does not move).

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Trik
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Nov 14, 2017 18:23 as a reply to Wilt's post |  #35

Temma : Good to know that, after initial focussing, no more is necessary when using a rail.

Wilt : I used the term "wide angle" because my lens is actually a 24 - 105 mm, and only suggested setting it at 50 mm as a possibility for using with extension tubes and/or reversed. Would that particular lens work at 50 mm reversed, though? Also, how can a reversed lens be manually focussed? Wouldn't it be going the wrong way? As you can tell, I have never got involved with this sort of technique and it is all very strange to me.

Trik




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Temma
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Nov 14, 2017 18:47 |  #36

Trik wrote in post #18496557 (external link)
Also, how can a reversed lens be manually focussed?

By moving the camera forward and backward with the rail.

I don't touch the focus ring on my reversed Minolta 50mm.

A lot of this is counterintuitive, but that's how it works.




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Trik
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Post has been edited 3 days ago by Trik.
Nov 14, 2017 19:13 as a reply to Temma's post |  #37

Do you set focus at infinity then, Temma? And do you think my 24 - 105 mm, reversed and set at 50 mm, would work?




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Wilt
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Post has been edited 3 days ago by Wilt.
Nov 14, 2017 19:13 as a reply to Trik's post |  #38

A 'reversed lens' is an ambiguously used term...it can be either


  1. a lens mounted to another lens, front-to-front, rather than directly to the body
  2. a lens mounted via an adapter which allows the front of the lens to be directly mounted to the body


The problem with #2 is that there is zero control of the lens' automatic diaphram, making it more difficult to focus with wide aperture and then stop down to shooting aperture at the moment of pressing shutter button.
In the case of #1, the lens mounted on the body in the conventional manner has its normal aperture control, but no focus control.

In either event, the focus distance is effectively set by the back of the lens, and the only way to 'focus' is to move camera+lens forward and back.

You need to give me OK to edit your image and repost! Keep POTN alive and well with member support http://photography-on-the.net/forum/donate.p​hp
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Trik
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Nov 14, 2017 19:20 as a reply to Wilt's post |  #39

Thanks for the explanation, Wilt, and for pointing out the disadvantage of #2.

I have thought of another drawback to a reversed lens, i.e. my Twin-Lite won't fit...




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Trik
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Nov 15, 2017 12:35 as a reply to Trik's post |  #40

I have been window-shopping and like the look of the Fotodiox Pro Extension Tubes (as suggested by Temma) and the Manfrotto Micro Positioning Plate (only forward and back but the adjustments can be less than 1mm according to some reviews I have read). Any thoughts on those choices, please, before I go ahead?

Thanks




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Photographing a moth egg - advice please
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