My personal macro and tele lens comparison

CrisPhoto wrote:

As promised, I took my Meike rings on the 75-300 zoom.

I took the usual picture of the wristwatch. But I noticed a strong red color shift in the dark tones. I noticed bad contrast in other pictures, but red was new as was the red cloth. Here is the picture, identical exposure settings, same Lightroom settings:

100% crops, @85mm/f11 Meike left, 124mm/f11 Marumi right.

I took the rings off and looked at the rings, they are black but very reflective. The contrast problems seemed familiar now: I had a microscope adapter for my OM-D which was essentially a black tube with mFT mount. But the black was reflective and gave very bad light effect in the center of every picture.

Same is with the Meike rings. You get a strong cast from the inner ring surface.

To give you an impression haw bad the rings shine on the sensor, I took a picture of the lens mount: normal light with simply a white sheet of paper before the lens. Note, the pictures do not exaggerate the reflection: The white paper you see through the lens is not overexposed and no other light source was in front of the lens, only paper.

Strong reflection inside the Meike rings, essentially no reflection on the lens mount without rings.

I think the current findings are very, very discouraging for the extension rings. Maybe other rings have better structured surface. Maybe I have a bad replica of the Meike rings? Anyhow, my rings are near to unusable, have to say it ...

Maybe someone has better rings and can post a photo how they are build?

On top of what you have already found yourself and what jalywol and I have already pointed out concerning the difference between your extenstion tubes and ours, you should perhaps additionally consider the impact of diffraction. Note that when you use extension rings, you effectively use a smaller f-stop than the one you set. See here under "lens extension & effective f-stop".

http://www.cambridgeincolour.com/tutorials/macro-lenses.htm

Note that the source I link to is far from always reliable but I think it's right in this particular case and don't have the time to find something better right now. Note also that the idea of diffraction is just an upshot. I haven't looked specifically for overall contrast differences in my own comparisons between close-up lens and extension tubes, and would like to take a second look at this when I have the opportunity. However, it may be a while before I have the opportunity to get it done.