Reverse Mounting + Extension Tubes

Reverse Mounting a Standard Lens Pt 2

Macro Photography by Reverse mounting a Standard lens + Extension Tubes

Equipment Used

In addition to equipment used in pt 1 I have added two EOS Auto' Extension Tubes of 31mm and 21mm length giving a total extension of 52mm.

These have been fitted directly into the camera bayonet-mount and the reverse adaptor lens assembly fitted into the end tube as shown below


This means the lens has moved 52mm further away from the sensor to check the new magnification a Rule with CM markings is brought into focus and image captured as shown below:


From the image of the rule you can easily see that the field of view is approximately 20mm wide on a sensor 36mm wide so the image has been reproduced larger than life size.

Magnification is 36/20 = 1.8 x


Full Frame images no cropping

Image © Phil Gee
ƒ1.4 @ 1/50th sec as metered


Image  © Phil Gee
ƒ22 @ 3.2 sec as metered

At these levels of magnification Dof or rather the Zone of 'Sharp' (Acceptable) Focus is measured in mm or less, it is symmetrically disposed about the Principal Plane of Focus at these levels of magnification.

One must remember what is considered 'Acceptable' is dependent upon the size of the final reproduction, viewing conditions, media, intended audience etc... guide calculations are based on Circle of Confusion (Blur Circle) enlarged approximately 8x and viewed from a standard viewing distance of approximately 25cm at which distance the Blur Circle should appear as a sharp point ref CoC notes.

Use the Histomation Technique to check exposure if using a Digital SLR, i.e. set display to show Exposure Histogram and check the shape and position of values if using RAW files you should be able to restore a stop or so of highlight values that appear to be over exposed i.e. at the RH end of the Histogram the display based on jpeg not RAW values.


Reverse mounting as a Supplementary