Reverse lens macro magnification calculation?

Started Jan 29, 2011 | Discussions thread
photonius Veteran Member • Posts: 6,895
Re: Reverse lens macro magnification calculation?

MagiCminDpt wrote:

photonius wrote:

hdngo1 wrote:

Would some one please let me know what is the magnification if I reverse a 55mm lens, and mount the front of the lens onto a crop sensor camera? Thanks

Reversing the lens and attaching it to the camera doesn't really give you much magnification. In fact, if the lens is a simple symmetric construction, it will be the same. The magnification you can get is obtained by using extension tubes between the lens and the body. If you have something like a bellows, it can make sense to invert the lens, since you have a lot of extension.

The other way to use a reversed lens is as a "close-up" lens mounted onto another lens. Magnification then depends on the lens you put it on.
A 55 mm lens would be about an 18 dipoter close-up lens, quite strong.

some more information here:
http://photonius.wikispaces.com/Close-up+%26+Macro

Er...
Nope.
BIG NOPE.

This is a ninfa os a Xysticus sp.
Taken with inverted Canon EF-S 10-18 at 10mm, on an A7 II body with an MC11 and a reverse ring:

This is the same, but using:
Canon 100mm + 50mm extension tubes + Raynox DCR-250
Magnification of 4,5:1

So as you can see you see we get a lot of magnification form inverting a lens onto the camera body...
ESPECIALLY wide angle lenses.

Image quality sucks, tough...

You misunderstood my posting. The 18 Diopter for a 55mm lens is when you use this lens like a close-up lens (in your second example this is the Raynox) on another lens (the Canon 100mm).  - And your example 4,5: 1 with your Raynox (which is 8 diopter) I consider very strong magnification.

For a simple reversed lens, magnification depends on the focal length, and the extension, similar to a normal lens. So, a 10mm lens, because of its short focal length, will be very "sensitive" to changes in distance from the sensor. With the simple thin lens formula, a 10mm extension plus focal length (10mm) for a total of 20mm from sensor to center of thin lens will already give a magnification of 1:1. Given you have already about 20mm mount - sensor distance (camera body), plus an adapter, and reversal ring, I'm not surprised that you get a very strong magnification.

PS: My info has moved to https://photonius.jimdo.com/macro/

And this is a really old thread

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