Cooke Mini S4/i's are also available with uncoated front or front/rear elements.
WHAT DO UNCOATED ELEMENTS DO?
The introduction of uncoated elements are a wonderful way to give a more vintage feel to your image, but what do they exactly do? Uncoated elements offer a look more similar to vintage lenses; exhibiting an increased sensitivity to lens flares, lower contrast from veiling flare, more flare artifacts in the optics chain, and a slightly softened edges.
Different strengths for different effects
The Cooke Mini S4/i lenses are offered in two different combinations: uncoated front elements and uncoated front + rear elements. While the intensity increases with the addition of the uncoated rear element, so does some uncoated side-effects I like to call 'gremlins'. Read more about these uncoated shooting tips after the examples below.
Cooke Factory Coatings
Uncoated Front Element
Uncoated Front and Rear
The uncoated rear gREMLINS
When utilizing both uncoated front and rear elements, the uncoated rear elements beautifully amplify the uncoated look as one can see in the above examples. However, they also exacerbate some of the uncoated caveats, which brings me to make this list of two situations to be aware of when shooting with Cooke and uncoated elements.
First, when using uncoated front + rear elements, the shape of the iris blades will become much more apparent and numerous within the lens flares. All of the above examples were shot at wide open T/2.8... this is the best stop to shoot uncoated rear elements on Cooke Mini S4's because the aperture is a perfect round shape when wide open. However, if stopped down, pay attention to your lens flares. Sometimes you won't mind a little Cooke iris shape buried in the madness, while sometimes you'll catch an angle just right where there feels like a giant polygonal shape is taking over half the screen!
The second situation to be aware of when using uncoated elements is when shooting a very bright object/subject within a darker scene. Now that there are more internal reflections in the optical chain, it is more common to see your lens flares not as out of focus balls/globs, but at particular focal lengths and focus distance, you may see some of the lens flares be small, inverted and sharp mini-reproductions of the object you are shooting. For instance, look at the example below. It is an 18mm, so the reflection is smaller, however, one can see a very small, upside down and sharp image of the window within the flare. Changing focal lengths, or moving considerably closer or further from the subject can put the mini sharp reflection out of focus, but it's at the expense of your original framing. It's rare but happens.
The following are links to public videos posted by other people or institutions that have Cooke Mini S4/i Uncoated Element tests/footage. They are not involved with CookeMiniRental.com and these links are just additional examples to what these lenses can do for your educational purpose.