DIY 77mm +0.33 Achromatic Diopter

• Diopter by AliExpress

Today we’re “making” a +0.33 - so low powered - 77mm achromatic diopter for $20. Diopters - or close-up filters - are auxiliary lenses that change how infinity works on lenses. They are incredibly useful for anamorphic shooting especially when it comes to close focusing, since most scopes struggle with that.

Diopters are great, but most of them - the cheap ones - are made of a single glass element. This leads to a good center performance and quickly decaying image quality as we move towards the edges. To address this issue, optical designers came up with Achromatic diopters. These are made of two glass elements one correcting the other’s imperfections, leading to much better overall performance, especially around the edges.

Low Powered diopters are rare by default and they are the most useful for us since we’re not trying to shoot macro here, we’re just trying to make a better looking medium close up shot. The math behind diopters is a bit too thick to tackle on this episode so I really recommend you read that article in the description.

Summarizing: achromats are awesome and low power is great. To give you some reference, one of the most famous diopters in the anamorphic world is the 72mm Tokina +0.4 Achromat. It sells for $250 on average, with peaks of $400. SLR Magic offers 77mm achromats in +0.33 and +1.33 for $100 each. Rapido just started selling its own 86mm +0.5 achromat for $350.

So it might be shocking to say we’re making a 77mm +0.33 achromat for twenty dollars. Let’s do this.

Go to AliExpress and order your glass! https://www.aliexpress.com/item/4000061253352.html?spm=2114.12010612.8148356.1.795b15daBxy1Nf

Mine took exactly 30 days to arrive.

In the meantime you can get started on the other ingredients. Get 77 and 82mm UV filters and knock out the glass. Then 3D print the file linked in the description.

Once the glass arrive, take a moment admiring it. Think that people want to sell you the same thing for 100 or more bucks and you just paid $10. Notice the division between the glass elements on the side. This is a thick piece of glass, eh?

Use a sharpie or permanent marker or model paint to black out the edges of the glass. This will improve light transmission and mainly contrast.

Then mount the glass on the 77mm blank ring and screw the 3d print in place. It should be safely locked in position. Lastly, throw in the 82mm UV so you get filter threads on top and you can mount other things to it!

There you go. Project complete. If you look at the coatings of this thing, you’ll see they’re a strong blue, which leads to eliminating a bit much of the blue lightwaves from the final picture. This means you’ll get a warmer image when using this filter.

This is much thicker than a single element diopter, but quite similar to SLR Magic’s diopters. Even in the coatings. Take that as you want.