Chronos > Chronos User Discussion

Let's talk LENSES!

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I admit I know very little about lenses.  When people have suggested certain lenses and adaptors,   it has just confused me even more!   It would be interesting to know
what people have used,  what has worked,   and what lenses work best for different applications like macro to zoom.   Trying to find the perfect lens can get very expensive,  so I hope
we can all learn from each other.   

My lenses so far:

Angenieux 10mm f1,8 Retrofocus
Kern Paillard Switar 25mm f1.4 (needs some modification)
Angenieux 15-150mm 1.9

All three of them have a native c-mount.

The 25mm Switar is the only one that needs some sawing of the outer frame to fit. It is because of the c to cs-mount adapter that has to be used. I think that if the camera would have a native c-mount it would not need the modification.
It is fairly easy modification to do, if you know how to use a saw or file.

All of them work fine after adjusting the back focus.

Hi TFM, I've been enjoying your content for years. 

I'm in kind of the same boat, never owned a camera before that didn't come with its only lens attached.  Well technically, I still don't (and probably wouldn't for stills unless/until my trusty WB850F dies).  I was likely the very last kickstarter and am still a few weeks away from receiving my Chronos, from the sound of things.  That hasn't stopped me from researching and shopping though.  I've taken the plunge on a Schneider Variogon 18-90mm f/2 from ebay and have already received a Belle & Howe Angenieux 25mm f/0.95 from Victoria Camera Traders (great guys and fast service there, btw).  Neither broke the bank, with both priced about the same as a new sample of the computar 12.5-75mm.  I'll hope the CS-C adapter I plan to get with my Chronos backsaces them properly, but we'll have to wait and see.

I was aiming to find lenses meant for 16mm and super-16.  The frame size of 16mm film is almost a match to the 2/3" sensor on the Chronos so there should be no vignetting and only a minimal cropping factor (a 50mm focal length lens for 16mm film frame should produce an image like a 58mm focal length lens on a 2/3" sensor).  Super-16 is pretty reasonable as well (a 50mm would behave like a 66mm).  Some good info is here and here.  I've been trying to think about the physics of it and while I think I kind of understand how the mismatch alters the field depth to behave like a different f-stop, I am inclined to believe this wouldn't have much impact on the light gathering performance. (if a 4/3" 50 mm f/2 lens is on a 2/3" sensor, we can expect it produce an image framed like 100 mm lens with the field depth of an f/4 aperture but I *think* it would provide the same contrast and brightness as though it were still on a 4/3" sensor at f/2. If anyone knows better, please, by all means, correct me. :) )  I've also noticed there's quite a bit of interest for vintage lenses in the Blackmagic Pocket Cinema Camera communities... its sensor is between 16mm and super-16 so their findings are quite valuable to us, as well.

Anyway, thanks for all the entertainment over the years.  That headspinning Chakotay still has my mind reeling like a block of clay after a silly putty slug. Once my camera is in, if you ever want a second angle, I'd be willing to make the drive from OC up your neck of the woods. Might give me the impetus to finally get my BFR45-70 fixed (or just say screw it and haul up the 460 instead)

C and CS mount lenses are an easy way to go but I have found that unless you pay "real" lens prices you are going to get quality somewhere between security camera and VHS, you get what you pay for.

I have been using a pair of C-mounts, an 8mm f1.3 and a 16mm f1.4 which are both good for a normal field of view, catching what you might expect to see when looking an an object within a few meters of the camera, the 8mm allowing you to fit an ~1m object in view at a distance of 1m.

For close cropped shots I have been using manual focus SLR lenses with a C-mount adapter, lenses like a 50mm f1.4 are great for catching outdoor subjects (birds or squirrels in a park). With the 50mm an object ~1m wide will fill the screen at a distance of 6m.

If the 50mm lens lets you focus at distances of 1m or less you can use it for macro shots of large insects, with an 80mm+ lens you can capture fairly small insects. If your lens wont let you focus at very short distances you have a couple of options, first is to buy a macro filter, these fit on most SLR lenses and make it so you can focus very close (almost touching the lens). If you don't want to use a macro filter you can use macro-rings/extension rings, these move the lens slightly farther away from the camera which makes the lens focus closer, they are made specifically for each lens mount BUT if you want to just hack it you might be able to get away with stacking 1 or 2 CS to C mount adapters. This will have the same effect as macro rings but may cut off the corners of your image.

For insanely high magnification I have used a 400mm f8 lens on the Chronos, it let me see a golfer teeing off from nearly 1km away and still have the ball visible. An ~1m object would have to be 50m away in order to fit on the screen at that point.

Finally, all of the "will fit on your screen" numbers only apply when you shoot at 1280px image width, when you increase the frame rate and shrink the resolution you will need to use lenses with shorter focal lengths to get a wider field of view. For example if I can see my whole shot with the 16mm lens at 1280x720 I will have to switch to the 8mm lens if I want to film at 640x360.

Hope this was helpful.

I'm hoping to get away with my Canon lenses - a 17-35/2.8L, 70-200/2.8L. 

Bought a Fotodiox C to EF adapter - nice quality. All I need now is the camera.

Also have a 17-85 Macro that was chucked in for free with a 2nd hand body I once bought because its electronics would fail and lock the body - glad I kept it.

I will be mainly analysing the strike of a golf ball and prelim calcs showed me the 17-35 will be good. The minimum focusing distance of 0.42m shouldn't change because of the crop, but the crop factor magnification is a godsend in making that golf ball occupy more pixels, so more accurate measurements can be taken.

Like ExaltedDuck, I believe the light gathering performance won't be affected by the crop - sure less total light will hit the sensor but each sensor pixel will still get the same exposure as it would have if the sensor was full frame.

I have done macro work before taping the 17-35 backwards to the 70-200, but depth of field is just too small for anything moving. I had the center of a fly's eye in focus, the outer parts way out of focus it is that small.


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