Minolta Maxxum 35-70mm F3.5-4.5 True Macro Modification

June 11, 2013 by CPBurrows

O  ne of the first things to interest me in photography was the world of macro. Before I got my first           DSLR, I had seen people’s super macro photos of flies and other insects, showing the facets and reflections in their eyes. I wanted that, but I certainly couldn’t afford to buy a true macro lens, which led me to seek an inexpensive alternative.
 
In my searches, I came across a mention on Flickr of converting a Minolta Maxxum 35-70mm F3.5-4.5 to a macro lens by removing the front element. I happened to have the exact lens with a half-broken plastic mount, ruining its resale value which was not high enough to warrant repair. I butchered it to see what he was talking about.
 
The results are not at all shabby, resulting in a lens with about 1:1.6 to 1.2:1 magnification ratio, satisfactory sharpness and retaining aperture control in-body. The working distance is actually better than that of the Sigma 50mm F2.8 Macro, around 6cm to its 4cm. It also transmits about half a stop more light than the 50mm and costs vastly less. It’s actually surprisingly close to as sharp, but exhibits fairly significant chromatic aberration, more or less digitally fixable.
 
Below are some test photos done with my Sigma 50mm F2.8 macro lens and my recently modified 35-70mm. Both groups of images were developed with 100% identical settings and are cropped identically with no scaling.
 
Below the test photos is a quick guide on converting this very inexpensive lens into a dedicated macro lens.

Sample Photos

Flower With Sigma 50mm @1:1
Flower With 50mm @1:1

Modified 35-70mm @ 35mm

Modified 35-70mm @ 35mm
Modified 35-70mm @ 70mm

Modified 35-70mm @ 70mm

Sigma 50mm @ 1:2

Sigma 50mm @ 1:2
Sigma 50mm @ 1:1

Sigma 50mm @ 1:1

Modified 35-70mm @ 35mm

Modified 35-70mm @ 35mm
Modified 35-70mm @ 70mm

Modified 35-70mm @ 70mm

Modification Instructions

This is actually a very straightforward modification, fairly obvious if you’ve got any experience taking things apart. Regardless, a little foreknowledge is always reassuring when it comes to risking breaking something you’d rather not. That’s mostly what this short instruction is about.
 
Before you start, there are a couple things you should know, and a few things you’ll need to have on hand. The process is entirely reversible but will take substantially longer to undo than it did to do. The front element assembly must be removed, and reinstalling it will require you to reset the ‘infinity’ focus for the lens. This isn’t entirely easy and is a tedious process. The lens will not be able to focus beyond about 6cm after the modification, making it a truly dedicated macro lens. You’ll need a skinny piece of metal like a scalpel or x-acto knife, a small phillips screwdriver, and a 49mm filter before you begin.
 

Here's the lens

First step, use your knife/sharp thingy to carefully remove the trim ring at the front of the lens. Try to do as little damage to it, the filter threads, and yourself as possible in case you want to reverse it or avoid a trip to the hospital.
 

Remove the screws

Beneath the trim ring are 3 small screws. These clamp a metal ring over the element assembly and part of the lens that extends. Remove these and keep them safe. Stick them on a magnet or in a baggie or pill bottle for safe keeping until later.
 

Helicoid removal

Now that the assembly is loose, you can twist it and it will unscrew from the helicoid. Loosen it some, and take the surrounding cylinder and rock it while pulling to remove it. If only one side comes out, pinch it and the other should be easy to remove too. Set it aside for a moment. Finish removing the element assembly and set it aside. It’s greasy, so set it on something disposable. You may want to wipe the top of the helicoid still in the lens body or it will deposit a ring of grease on your filter installed in the next step. It doesn’t hurt anything if it does.
 

Last step

Remember the surrounding cylinder from the last step? Grab that guy and slot the two tabs on its base into the grooves in the lens. Try to do this upside down to prevent dust from falling into the lens. Again, you may need to pinch the cylinder to get it to slot in. Screw that 49mm filter onto this to keep dust and debris out and you’re ready to go shoot some macro. Make absolutely sure to turn off autofocus on your camera before mounting this lens or you’ll risk damaging the autofocus motor.
 
Here’s my end product.

End Result

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