Reversing EF lens on macro lens

I believe I understand how to reverse one lens on another to

increase magnification for macro (use male-to-male coupler), but am

not sure what the pros and cons are of using various lenses in the

reverse position. I have a Tamron 90mm macro lens; I also have the

EF 50/1.8 and 24/2.8 lenses which are my candidates for reversing on

the front of the Tamron. What are the tradeoffs of the two primes in

the reversed position? I just want to buy one coupling ring at this

point and these two lenses are different sizes. Thanks!

<p>I've actually become interested in the same thing. I've been experimenting without a coupler, just leaving one lens resting a couple of centimeters above the object. There are a number of different factors involved in getting the best results and in getting the highest magnifications. My macro lens, a Canon 100mm F/2.8 (non-USM), actually didn't end up being the best for what I was doing because the built-in hood limited proximity to the other lens, I found I wasn't focusing anywhere near !:1 or even 1:2, and I found that a longer focal length lens on the camera gave me better magnification. With my rather crude setup, I was able to capture a segment of a dime at a magnification of 15x, though it wasn't especially sharp, and depth of field was a significant issue. For this I used a 70-200 F/4 with a 2x extender zoomed to 400mm with a 28-90 USM II positioned a couple of centimeters over the dime and set at 28mm. I got some decent results from using a 50mm F/1.4 over the object as well, but I was not getting as high a magnification as with the 28-90. One benefit of using the 2x extender was the ability to stop down to F/64.

I also stopped down the 28-90 by putting it on a cemera, stopping it down, taking a long exposure, and turning off the camera before the shutter closed. I am not recommending this because it may not be good for either camera or lens, but it seemd okay, and I am comfortable taking risks with my 28-90 and my Rebel 2000. Anyhow, the shots I took with my 10D were not terribly sharp at 15x, but when I shrunk them in photoshop and compared them to scans of the dime I made at 4800 ppi on my Epson 4870, the 10D pictures were dramatically sharper.

I also did the same with samples of a slide compared with samples scanned with my Nikon LS-5000 at 4000 ppi, and the pictures from the 10D were clearly sharper when reduced to match the Nikon scan.

<p>My advice to you would be to set up your lenses as I did without actually coupling them in order to get a sense of how your particular combination of lenses seems to be working for whatever your subject. This is definitely one of the more accessible ways to achive high magnifications, although it is not especially easy to take great pictures with such a shallow depth-of-field and awkward working distances. After you try it out thihs way, you'll have a much better sense of what to expect with a coupler.

<p>IMHO, if you cannot achieve or do not need a minimum of 2-3x magnification, then you would be much better off with extension tubes and diopters.

<p>I am interested in what combinations others have found to work well.

 

<p>HTH,

 

<p>Brian

Philip:

 

Some combinations of lenses are better than others. You have to test each combination to see how well it works. A 50mm lens reversed on a 90mm lens will give you 1.8x magnification. A 24mm lens reversed on a 90mm lens will give you about 3.8x magnification.

 

Handhold both combinations (no coupling ring) to get an idea how they work together.

 

A 25mm extension tube and a 2x teleconverter with your 90mm macro will give you up to 2.8x magnification and will be easier to work with.

 

Jim

To give you some idea of what you could get, here is quick snap shot of part of a dime taken with a 105/2.5 (@f5.6) & EF24 reversed (at f4). You may want to change the EF24 aperture buy removing the lens while depressing DOF preview buttom. It is easier that way.<div></div>