Chronos > Chronos User Discussion
Let's talk LENSES!
BiduleOhm:
Even without a reducer you can still use it without any problem, you just need to put the camera farther away and/or use lens with a smaller focal length ;)
Dan Kanes:
Sorry , no.
Crop factor is a bad idea that confuses people about how lenses work.
What he was saying is you need a 50mm lens made for a 2/3" sensor, and that a 50mm lens for a 2/3" sensor would have a different field of view than a 50mm lens made for a 35mm sensor.
Go get a 50mm 16mm format lens, a 50mm 35mm lens, and a 50mm 2/3" lens - they will all provide the same field of view on the Chronos - because they are ALL 50MM LENSES.
Now, your understanding of effective crop factor is sort of an okay way to translate concepts - but you get into a real shitstorm when you realize there are a lot of 35mm formats and you start making decisions about a shot size on incorrect understandings of how lenses function.
It's better to think in "wide, normal, and telephoto" terms if you're just starting out.
A wide on the Chronos could be anywhere from 6mm to 12mm pretty much.
A medium on the Chronos would be 16 , 25 or 35 (with 35 being pretty long actually)
Telephoto could be a 50 and above on Chronos.
On a 36x24 film format a 50mm is a "medium"
And on a super-35mm motion format a 35 is pretty much "medium"
You could try learning with this whole crop factor BS that photogs often lean heavily on, but if you want to learn the more scientific way that won't leave you with incorrect assumptions - watch the Abelcine video with mitch gross that I posted.
I hate crop factor because it always confuses people new to motion imaging and is akin to trying to translate every word in a foreign language before learning a native language.
--- Quote from: BiduleOhm on July 21, 2017, 04:04:43 AM ---
--- Quote from: Dan Kanes on July 20, 2017, 04:44:23 PM ---A 50mm lens made for a 35mm camera will offer the same field of view as a 50mm lens made for 2/3" or 16mm.
--- End quote ---
Actually, no, the "A lens is a lens is a lens, and it doesn’t know what size sensor or film gate is placed behind it." is exactly why we have the crop factor. Please see https://photographylife.com/what-is-crop-factor and https://www.bhphotovideo.com/explora/photography/tips-and-solutions/understanding-crop-factor and https://en.wikipedia.org/wiki/Crop_factor
This means that for our 2/3" sensor the crop factor is almost 4, so a 50 mm lens on 2/3" sensor will have the same effect as a 200 mm lens on a 35 mm sensor, and what ExaltedDuck said is spot on (except the reference sensor isn't 4/3" but 35 mm).
--- End quote ---
ExaltedDuck:
FWIW, The way I think of it is in terms of the resolved image circle's diameter and whether that is relatively similar to the sensor's widest dimension (diagonal). If the circle is smaller, there will be vignetting, if it's similar, the lens should work as expected, and if it's larger then the edges of the resolved image are not captured, reducing the field of view. I tried to keep the language similar to how photographers describe things because that is what we will find if we look into photo/videography forums for ideas as to what might work on our cameras as well as being consistent with how the topics were approached in the links I offered.
Anyhow, I don't want to jack the thread from its original intent: discussion of which lenses we've chosen for our cameras, and why. I wanted to try a prime and a zoom, I wanted something native C-mount to (hopefully) minimize hassle, I wanted it to be intended for at least a 16mm film size to minimize likelihood of vignetting but no bigger than super-16 to ensure that as much as possible of the objective lens's light gather capability is focused on the sensor. I wanted to find something not much more expensive than the Computar 12.5-75 and I was willing to settle for maximum aperture around 1.8-2.0 as long as it was from a notable name in optics. I looked at many possibilities on ebay, bhphotovideo, and a few other sites. I preferred to buy second-hand so that if I am unhappy with the results, I should be able to recoup my costs and redirect the money to something else. Those models I chose met all of my criteria. I have high hopes for both and anxious to try them out when my camera gets here in a few weeks.
BiduleOhm:
@Dan Kanes I'll not argue more on the subject and I'll wait to have the camera and some F-mount lenses (already bought a F to C mount adapter) to compare to some real C-mount lenses (actually the Computar 12.5-75 mm and some other small lenses for CCTV) so I'll see by myself who is right.
@ExaltedDuck As said I have the Computar 12.5-75 mm f1.2 which should be perfect for most shots (excepted macro maybe) and I have some small CCTV lenses I was using for CCTV but maybe one of them will do good on the Chronos (or maybe they're all too crappy...) :)
Electra:
I'd have thought that the focal reducer/speed booster would have been more useful because it gives you another F/stop? Are there such things for C mount or is this going to be Krontech's next custom made accessory? :)
That's why I was looking at them. If you take a lens for a 4/3 or full frame sensor and focus all that light on the 3/4" sensor the Chronos has, it'll give you much better light gathering capabilities, the one thing that your always fighting for with high speed cameras.
Getting second hand glass for much larger sensors is fairly easy due to the SLR market, but a lot of the light is lost using it with the smaller sensor size. It would be nice to get some of it back even if it means quite drastically changing the lens focus length.
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