Joined: 15 Jan 2018
|Posted: Fri Feb 14, 2020 4:51 am Post subject: Apo Objectives: Edmund Optics 10x VS Mit MPlan 10x
|Here I will compare the 10x Mitty to the 10x Edmund Optics objective lens, both which are apochromatic. I'll also discuss the limitations/improvements of the test, as I think there's some problems with my setup.
View the 20x comparison here: https://www.photomacrography.net/forum/viewtopic.php?t=41092
I do have the 50x and 100x EO objectives, no Mitty to compare them against, I also don't have an adequate setup to handle 50x and 100x stacking.
The EO10x is $740 while the Mitty 10x is $900. A $160 difference, not a lot. Both copies were purchased new.
I use a mask with square patterns to test CAs. LoCA can also be determined this way. For sharpness, I use a silicon chip.
Using Thorlabs/Nikon ITL-200 as tube lens, the Mitty 10x:
Some CA in both the centre and extreme corners. The corners are pretty soft while the centre is great. An expected result.
ITL-200, EO 10x:
The centre is perfect, better than Mitty 10x. The corners are the same, rather soft.
I didn't expect the EO 10x to do that well. However, eagle-eyed viewers might have realised a small discrepancy, the direction of the edges in the CA crops.
Here, I've cropped out the full square, with rounded edges.
There's some stuff to note:
- ITL-200 yields a higher magnification, not sure why. I've measured everything with accordance to Thorlabs' setup recommendation. This shouldn't happen. Definitely something went a bit wrong
- The edge on the left has less CA than the right, this is the case for both crops. However, the EO is indeed better.
Moving on to the Alphatube, Mitty 10x:
Some CA, excellent sharpness in the centre. The corners aren't half bad, I'd say it's acceptable.
Now, the EO 10x:
Centre is great, corners are alright. The Mitty 10x is clearly better, however certainly not by much.
While overall, the Mitty 10x is solid, the EO 10x doesn't fall behind at all. Is the Mitty worth that extra $160? Hard to tell. If the EO 10x is made to be robust, then I'll certainly recommend it. The EO falls short on its presentation, cheap dinky case, a joke of a serial number that's just some sticker... That aside, both are solid performers.
My next step is to investigate the ITL-200 problem and redo the Mitty 10x shots using that tube lens. The higher mag puts the Mit in a slight disadvantage.
The setup needs improvement too. In the CA shots, the edge facing the light source consistently yields worse results compared to the ones facing away. I need to configure my system to do true backlighting. Currently, I have the mask sitting on a transparent box, the light source shines onto a white surface beneath it, creating uneven illumination. Light also spills onto the mask as well. I will have to custom order an adaptor plate for my stage, can't do it now because of the virus in China.
The adaptor plate needs an aperture opening on the bottom. I currently have the stage mounted to a 150x150mm Newport breadboard via a heavy racket (so 2 pieces of metal) that clamps into a set of Thorlabs RLA rails (this makes 4 pieces of metal, while only one is necessary!), the pieces sit on my Thorlabs vertical stage, just barely exceeding the weight limit. Having a proper adaptor plate will allow me to light up the masks from the bottom.
After all this is done, I'm going to make a detailed blog post. At the moment, I'm happy to recommend both objective lenses. 100x will be coming soon, I'll run some manual stacks using my 0.5um stage, the good'ole way. I can't retest the EO lenses anymore, they are being used elsewhere.
Personal Flickr page: https://www.flickr.com/photos/133023063@N04/
Blog still under construction
Last edited by Macro_Cosmos on Fri Feb 14, 2020 9:40 am; edited 1 time in total