Photo of a succulent plant. Image by Eduardo Libby

Is it better to mount Canon’s 500D Close-up filter in reverse?

Here and there I’ve read in the internet that mounting Canon’s 500D close-up filter in reverse gives you better image quality.  So, I tried it…

Even though I own a nice 105 mm macro lens, I don’t always carry it with me: There is a physical limit to what you can put in your backpack! However, when I don’t, I always make sure I have a quality close-up filter for my telephoto zoom lens.

The trick I always do to get good image quality is to stop-down the lens a bit and also keep the lens focused close to the infinity mark. Zoom lenses are great for macro photography because you can change the magnification without having to move your lens (and tripod) forward or backward. Nikon used to make a true macro zoom lens but it is long discontinued now, and used ones for sale have become very, very rare.

So, what happens if you reverse mount the filter? Some people unscrew the lens holder and mount the filter backwards, but I simply mounted it with adhesive tape for the experiment. What I found out is that, with slow lenses like the popular Nikon AFS 70-300 or the AFS 80-400 (about f/5.6), mounting it one way or the other does does not make a big difference, and it is always advisable to stop down the lens a bit.  However, when I tried it in my Samyang/Rokinon 135 f/2, where I cannot get a sharp close up image with the filter unless I stop down to at least f/4, reverse mounting it does make the images I get at f/2 almost as good as the ones I get by closing down one or two stops. Now I can  have this lens’s beautiful Bokeh in the macro range!

All is not good news though: the flatness of field does decrease a lot by mounting the 500D filter in reverse. Now, this might not matter for three dimensional subjects but it’s something to keep in mind should you need to photograph flat objects.

 

Photo of Rivinia humilis (Phytolaccaceae) fruits. Image by Eduardo Libby
I made this photo using a Nikon Close-up filter and my 70-300 mm zoom lens at a large aperture to isolate the fruits from the background. I did focus stacking to keep most of the fruits sharp.

 

Using a computer screen to reveal the focus field. Image by Eduardo Libby.
I photographed my computer’s screen at close range using my Rokinon 135mm f/2. The sharply focused area (where the field of focus is flat) is red due to Moire interference. Notice how in the first picture, taken at f/2 with the normally mounted close-up filter, nothing is really sharp but stopping down rapidly creates a large sharp area. In the second row, with the filter mounted in reverse there is a sharp zone even at f/2 but it does not widen as much by stopping down. This is useful if you want to isolate your subject but not so good for keeping a flat object sharp.

To sum up: Do use top quality close-up filters to save weight… and get as close to using a true macro zoom as you can. Just stop down a bit and don’t try to focus your lens too close. Experiment to know the  limits of your equipment. If you have a slow lens or if you need to photograph flat objects, do not bother mounting Canon’s 500D filter in reverse. In this case, you will be stopping down your lens anyway.

Canon’s 500D is a great close-up filter and a good purchase… and it is a Nikon user who says it!

 

 

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