RogerBW's Blog

Polaroid macro lens set 04 September 2017

I picked up a cheap set of macro lenses for the GF1.

There are four of them, and they're simply screwed on to the front of an existing lens. Here are some attempts at the same close subject (a Finnish handmade iron mouse on top of an infra-red remote controller) with different magnifications. The snout of the mouse is about 3mm wide at the tip.

Without enhancement (45mm focal length, equivalent to 90mm on a 35mm SLR):

+1 dioptre:

+2 dioptre (I think I must have pulled back a bit for this one):

+4 dioptre:

+10 dioptre:

As the magnification increases, depth of field drops off sharply.

As you'll guess from the numbers, the lenses can be stacked together (strongest at the front, as the +10 bulges significantly out of its frame). So here I've combined them all for +17 dioptre on 45mm:

And, just for excessiveness, +17 dioptre in front of 200mm (400mm equivalent in 35mm terms):

This would obviously benefit from a tripod, not so much because of camera shake, but because of the knife-thin depth of field; I found myself leaning forward and back to get to a range where the autofocus could manage to lock on.

Now, clearly this isn't the usual extension tube approach to macro photography, which would increase the distance between lens and camera body; image quality relies on the optics of the magnifiers. On the other hand, it's vastly cheaper than a tube that would pass through the control channels for lens electronics; it comes in a slim wallet that fits in my camera bag; and it's not tied to this specific camera and lens system, but will work with anything with a 52mm front.

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  1. Posted by Owen Smith at 11:58am on 04 September 2017

    Note that these macro add on lenses and also extension tubes suffer a problem peculiar to mirrorless cameras, or at least micro four thirds. Lenses for the system don't have to be optically correct, the camera applies corrections in real time in software for both the viewfinder and the saved JPEGs. The camera does this by knowing the non linearities and chromatic abberations of the lens based on data the lens passes to the camera body (there are detail differences between how Olympus and Panasonic do this which I won't go into here). As soon as you put magnifying lenses on the front or extension tubes on the back, those corrections become wrong. How wrong I wouldn't like to say. Raws are saved as is but include the correction data, and most raw developing software applies them. You can find raw processing software that either won't apply the corrections at all or can switch them off.

    I have a set of micro four thirds extension tubes which pass the electronic connections through. I've used them precisely once, you can borrow them to play with if you want and see how much better or worse they are. They didn't really do what I wanted. I was trying to take pictures of RPG figures with a real life like perspective, which needs about an 11mm focal length on micro four thirds but neither my 12-32mm nor 9-18mm lenses would focus close enough. With the 10mm extension tube on they wouldn't focus anything far enough away, and you can't get extension tubes thinner than that. I ought to try again with the Olypmus 12-40mm Pro lens I bought a year ago, it focusses really close anyway. So close I have to take the lens hood off to find the limits of it's close focus.

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