The EO objectives come in a cheap case, I like the heavy duty case Mitutoyo objectives offer. The serial number on the EO objectives are a piece of sticker, and only one week of use, the text already faded. Nice job... As long as there's an invoice I guess, but how would they distinguish between different serials if the number fades so easily? Moreover, what's the repair policy? I do not know, we are going to handle these with care.
To compare the two objectives, I used my setup and the following photographic interests:
- Mask with diffraction gratings of various frequencies, LoCA
- Mask with square segments, CA
- Silicon chip, sharpness
My setup is vertical, the camera setup is mounted on a manual linear translation stage that offers .5um resolution. I used two tube lenses, my custom tube lens (calling it the alphatube for now) and the Thorlabs ITL-200. My Mitutoyo 20x does have some issues, it's likely decentered. Nonetheless, I wanted to see the matchup. I need to retake the diffraction grating shots, those will be posted later.
Let's look at the square mask first, which illustrates the CA of the objectives.
EO on the top, Mit on the bottom, Alphatube.
Both of these objective lenses have quite the colour fringing, however for such a subject under such circumstances, the issue is exacerbated. The Mitty 20x gets a score here, less CA, not by much. Bottom left and right looks as if it's out of focus, it's the best I could get.
Now, time for the ITL-200. EO on top, Mit on bottom.
The result is the same. The Alphatube coupled with the EO performs better than the ITL-200, for mitty, the two are almost indistinguishable.
For sharpness, a silicon chip was used. Starting with the Alphatube, EO on top and Mit on bottom:
The EO is definitely sharper in the centre. The EO has an edge in the corners too, however not by much. Both objectives have poor corners.
Now with the ITL-200, EO on top and Mitty on the bottom:
The EO is sharper in the centre, while the corners are worse than the Mitty.
It's pretty clear here, my Mitty is somewhat decentered. One set of corners consistently outperform the other. The set will depend on the orientation of the objective lens. A new Mitty 20x should be expected to do better. Is the EO 20x worth that $300 saving? You be the judge.
The CA doesn't matter in the real world in both scenarios, however it's fair to say that the Mitutoyo 20x is better corrected for CA than the EO branded 20x.
The 10x comparison will be posted tomorrow. My Mitty 10x was purchased new, which gives the comparison more explanatory power, since we're comparing 2 objectives that are essentially new. I don't have the Mitutoyo 50x or 100x objectives to compare against my EO ones.