Chronos > Chronos User Discussion

F-stop when using lenses from 35 mm camera

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ratas calientes:
Folks - first post here - my camera arrived a few weeks ago.  Still rounding up other gear to put it to use.

Question . . . I already have a few old FD-mount (Canon) lenses . . . particularly a Vivitar Series 1 28-105 mm and a 70-210 mm.  I also have a C-FD adapter.  On using these lenses . . .  does the f-stop change?  If I set the Vivitar lens to f/4, does that still equate to f/4 on the Chronos?

Thanks - Glenn

Simon:
Hi - crop factor affects both focal length and f-stop - so f/4 on a 35 mm sensor will look like f/16 on the Chronos' sensor.

tesla500:

--- Quote from: Simon on October 06, 2017, 09:56:01 PM ---Hi - crop factor affects both focal length and f-stop - so f/4 on a 35 mm sensor will look like f/16 on the Chronos' sensor.

--- End quote ---

Unfortunately that's not correct. F-stop does not change with crop factor. f/4 on a 35mm sensor is the same as f/4 on the Chronos sensor. The only way the f stop will change is if you are using a speed booster.

Effective focal length will change, for example Chronos is about a 4:1 crop factor from 35mm, so a 28mm lens on Chronos would be like a 112mm lens on 35mm.

Simon:
As far as how it looks to the sensor though, won't that 28 mm f/4 lens on a Chronos collect the same light (noise) and have the same depth of field as a 112mm f/16 lens on a 35mm? As in the resulting image taken on a 112mm f/16 on a 35mm body would look the same as a 28 mm f/4 lens on a Chronos?

thebishop:

--- Quote from: tesla500 on October 07, 2017, 12:27:51 AM ---Effective focal length will change, for example Chronos is about a 4:1 crop factor from 35mm, so a 28mm lens on Chronos would be like a 112mm lens on 35mm.

--- End quote ---

Wouldn’t that be the other way around, a 28mm on a full frame camera would be 112mm on the cropped sensor of the Chronos?

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