Ryan Patrick O'Hara
Veteran
Hey everyone!
As many of you Cine-lens users may know, Cooke has a set of MiniS4/i lenses, which are like S4's but a stop slower, smaller in size, lighter in weight and less expensive to buy and/or rent. The image circle of these lenses are advertised at 33.54mm, which covers Epic 5k no problem. However, with the arrival of the new Red Dragon and a larger sensor, the newly required 34mm image circle is a hair out-of-spec for the MiniS4/i's image circle... on paper, that is. Considering many Red Epic users have been using lenses designed for sensors smaller than Epic 5K at the 5k sensor size(for better of for worse) I figured I'd run these lenses through the gauntlet to see if the unintentional portions of their image circle covered the extra .5mm of the sensor.
The first intention of this test is to simply see if the image circle of the lenses cover the sensor, and if so, to get an idea of what kind of increased uneven field illumination is introduced in the peripheral of the image. I focused all lenses to an arbitrary focusing distance of 7' and tested mainly at wide open apertures, the aperture which will show the most uneven field illumination from center to corner.
I built a custom testing rig in order to get a soft and even light to illuminate an opaque surface upon which the lenses would fill within their field of view.
The results where very informative, however I must reiterate the 'light box' I built was homemade. Although the illumination was very close to being uniform, all variables that could introduce a false increase in uneven field illumination within the test is possible. I also attempted to keep exposure as consistent as possible when going between T/2.8 and T/8. I used the shutter to compensate between exposure settings.
See the setup below:
See the test results:
Observations:
1) The 18mm MiniS4/i surprisingly had slightly better coverage than the 25mm MiniS4/i. Both produce a hard vignette in corner at 6k Full frame, but not at 6k HD.
2) At 6k Full Frame, at T/2.8, the 32mm and longer lengths offer moderate to unnoticeable uneven field illumination.
3) As you stop the lens down the uneven field illumination cleans up quite a bit. (see T/8 examples)
4) At 6k Full Frame, when at T/2.8, heavy uneven field illumination yields at 32mm and at 50mm (and longer) becomes a non-issue.
5) At 6k Full Frame, the 25mm always hard vignettes in the very extreme corners.
6) At 6k HD and at T/2.8, every MiniS4/i covers the sensor without hard vignetting.
7) At 6k HD, the uneven field illumination is moderate at an 18mm and 25mm. It is significantly improved at 32mm and is almost completely absent from 50mm and longer.
7) At 6k HD, and stopped down (see T/8 examples), any significant uneven field illumination is absent on all focal lengths.
My first expectation which was thrown out the window was the 25mm behaving better than the 18mm. That was not the case! Typically, the optical designs of wider focal lengths do not allow for as much 'unintentional image circle' other lenses can have, typically telephoto. The surprise in this test is that the 18mm did not hard vignette at 6k Full Frame as much as the 25mm did. As it turns out the 25mm struggled the most to fill Red Dragon at 6k Full Frame.
However, all Mini-S4's covered the sensor without a hard vignette while at 6K HD. When wide open, the unintended image circle in the far corners can exhibit some moderate uneven field illumination on the 18mm and 25mm lenses. When stopped down slightly or using a 32mm or longer, the results drastically improve.
That said, the results were solid and if I were to ever shoot with these lenses on an Epic Dragon, which I'm sure I will, I would adhere to the following rules of thumb:
1) Can shoot any MiniS4/i lens at 5.5k and below.
2) At 6K Full Frame, avoid the 18mm and 25mm. However they work at 6k HD with some moderate uneven field illumination.
3) At 6K HD, I would accept any of the miniS4/i lenses. However I would consider closing the 18mm or 25mm down a tad to mitigate the slightly elevated uneven field illumination if it's an issue.
**Special thanks to Blacklist Productions in Hollywood, CA for letting me take over one of their prep rooms and steal one of their Red Dragons for the day. **
As many of you Cine-lens users may know, Cooke has a set of MiniS4/i lenses, which are like S4's but a stop slower, smaller in size, lighter in weight and less expensive to buy and/or rent. The image circle of these lenses are advertised at 33.54mm, which covers Epic 5k no problem. However, with the arrival of the new Red Dragon and a larger sensor, the newly required 34mm image circle is a hair out-of-spec for the MiniS4/i's image circle... on paper, that is. Considering many Red Epic users have been using lenses designed for sensors smaller than Epic 5K at the 5k sensor size(for better of for worse) I figured I'd run these lenses through the gauntlet to see if the unintentional portions of their image circle covered the extra .5mm of the sensor.
The first intention of this test is to simply see if the image circle of the lenses cover the sensor, and if so, to get an idea of what kind of increased uneven field illumination is introduced in the peripheral of the image. I focused all lenses to an arbitrary focusing distance of 7' and tested mainly at wide open apertures, the aperture which will show the most uneven field illumination from center to corner.
I built a custom testing rig in order to get a soft and even light to illuminate an opaque surface upon which the lenses would fill within their field of view.
The results where very informative, however I must reiterate the 'light box' I built was homemade. Although the illumination was very close to being uniform, all variables that could introduce a false increase in uneven field illumination within the test is possible. I also attempted to keep exposure as consistent as possible when going between T/2.8 and T/8. I used the shutter to compensate between exposure settings.
See the setup below:
See the test results:
Observations:
1) The 18mm MiniS4/i surprisingly had slightly better coverage than the 25mm MiniS4/i. Both produce a hard vignette in corner at 6k Full frame, but not at 6k HD.
2) At 6k Full Frame, at T/2.8, the 32mm and longer lengths offer moderate to unnoticeable uneven field illumination.
3) As you stop the lens down the uneven field illumination cleans up quite a bit. (see T/8 examples)
4) At 6k Full Frame, when at T/2.8, heavy uneven field illumination yields at 32mm and at 50mm (and longer) becomes a non-issue.
5) At 6k Full Frame, the 25mm always hard vignettes in the very extreme corners.
6) At 6k HD and at T/2.8, every MiniS4/i covers the sensor without hard vignetting.
7) At 6k HD, the uneven field illumination is moderate at an 18mm and 25mm. It is significantly improved at 32mm and is almost completely absent from 50mm and longer.
7) At 6k HD, and stopped down (see T/8 examples), any significant uneven field illumination is absent on all focal lengths.
My first expectation which was thrown out the window was the 25mm behaving better than the 18mm. That was not the case! Typically, the optical designs of wider focal lengths do not allow for as much 'unintentional image circle' other lenses can have, typically telephoto. The surprise in this test is that the 18mm did not hard vignette at 6k Full Frame as much as the 25mm did. As it turns out the 25mm struggled the most to fill Red Dragon at 6k Full Frame.
However, all Mini-S4's covered the sensor without a hard vignette while at 6K HD. When wide open, the unintended image circle in the far corners can exhibit some moderate uneven field illumination on the 18mm and 25mm lenses. When stopped down slightly or using a 32mm or longer, the results drastically improve.
That said, the results were solid and if I were to ever shoot with these lenses on an Epic Dragon, which I'm sure I will, I would adhere to the following rules of thumb:
1) Can shoot any MiniS4/i lens at 5.5k and below.
2) At 6K Full Frame, avoid the 18mm and 25mm. However they work at 6k HD with some moderate uneven field illumination.
3) At 6K HD, I would accept any of the miniS4/i lenses. However I would consider closing the 18mm or 25mm down a tad to mitigate the slightly elevated uneven field illumination if it's an issue.
**Special thanks to Blacklist Productions in Hollywood, CA for letting me take over one of their prep rooms and steal one of their Red Dragons for the day. **
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