Author Topic: Let's talk LENSES!  (Read 2911 times)

BiduleOhm

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Re: Let's talk LENSES!
« Reply #15 on: July 23, 2017, 04:50:49 AM »
I searched for a bit and I can't find a F to C-mount focal reducer. I guess we need to ask on photography forums if this kind of focal reducer exists.

Electra

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Re: Let's talk LENSES!
« Reply #16 on: July 23, 2017, 09:04:14 AM »
Some info on how they work: http://rubenkremer.nl/2013/11/26/focal-reducers-speedbooster-lens-turbo-and-light-cannon/
https://beomagi.blogspot.com.au/2014/01/focal-reducers-on-dslrs-and-light-gain.html
And a bit about them on more conventional cameras:  http://nofilmschool.com/2014/07/cheaper-budget-metabones-speed-booster-excell-1-fotodiox-pro

I did find: http://agenaastro.com/agena-c-cs-mount-focal-reducer.html
There looks to be a whole range for telescopes. Might be worth looking down that path.

Because we'll be doing something non-standard, I'm expecting half research and half trial-and-error to get this working, but unless I've got something very wrong, it should possible.
Depending on the lens/adapters, we may have to find native reducers for our lenses and then something like that c mount one for the final to get past the adapters narrowest point. One thing that might help is that C mount is made for 1" sensors(or close to it) and we have a 2/3" sensor, so even if we loose some light, concentrating what we can use further might still help.

I know there'll be looses in the optics and I'm expecting most bother, but it's too interesting a path to not at least experiment a bit.

BiduleOhm

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Re: Let's talk LENSES!
« Reply #17 on: July 23, 2017, 10:07:34 AM »
Yeah I found this one too but it's for a 1.25" telescope mount, I don't think it'll be very useful here unfortunately.

Yes, if you can find the proper reducer then it'll work no problem. The main problem is to find one for a C or CS mount and where we can mount a Canon/Nikon lens (EF or F mount) on the other side even if we need another adapter. For now I only found 1.25" to C mount reducer or some DSLR to another DSLR reducer.

nik282000

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Re: Let's talk LENSES!
« Reply #18 on: July 23, 2017, 06:02:37 PM »
Hmm, a speed booster is an element on the back of a lens compresses the image circle. So what do you call an element in front of the lens that compresses the image circle? A fisheye filter!

If you can find a strong enough fisheye filter it would give you both a wider FOV and more light per pixel on the sensor (provided that the aberrations from filter aren't too bad). Given that the Chronos sensor is 2/3" many of the aberrations from a filter may fall outside the sensor area anyway. Looks like there are a couple on ebay/amazon for <$100 but I have never personally tried one.

Any thoughts?

John DeLonghi

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Re: Let's talk LENSES!
« Reply #19 on: July 24, 2017, 06:08:45 AM »
My experience of fitting wide angle adapters to the front of lenses has never been particularly good. The optical performance is usually not very good and as they are often designed to be 'universal' they take no account of the construction of the lens they're being fitted to.
There are some good ones around but they are quite expensive and I don't think the end result will be as good as if we can find a focal reducer.

I also spent some time over the last few days trying to find a decent reducer to fit the Chronos with no real success. There won't be any demand for such a thing at the moment, but if there was a way to adapt something like a Metabones Speed Booster, I'd go for it.

I think it should be technically possible to adapt a Speed Booster designed to take Nikon G/F mount lenses to fit the Chronos, but the missing link is converting one of their camera-side mounts to C/CS.

BiduleOhm

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Re: Let's talk LENSES!
« Reply #20 on: July 24, 2017, 11:32:21 AM »
What's their camera side mount?

John DeLonghi

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Re: Let's talk LENSES!
« Reply #21 on: July 25, 2017, 03:54:21 AM »
They do various versions, all for mirrorless cameras such as Leica M/S Sony E, Fuji X.

I reckon the best bet might be the versions they do for MFT or Blackmagic as those are small diameter mounts to begin with. It might be possible for someone to machine a mounting ring which would replace their one and convert directly to C mount.

There are lots of adapters out there for fitting C-mount lenses to MFT cameras, but not the other way around.

nik282000

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Re: Let's talk LENSES!
« Reply #22 on: July 25, 2017, 10:24:48 AM »
It all has to do with the back focus distance, with mft and e-mount I believe the cmount adapters extend into the body of the camera. To make an mft or e-mount to c-mount I think that means there will be a couple mm of space in which to make an adapter.

Welp, looks like the flange to sensor distance for all 3 mounts are 17-19mm, not much room to work but not impossible.
« Last Edit: July 25, 2017, 10:36:07 AM by nik282000 »

John DeLonghi

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Re: Let's talk LENSES!
« Reply #23 on: July 25, 2017, 10:55:02 AM »
That's why I thought it might be possible with one designed for MFT in the first place. It's bound to be tight, but 17.5mm seemed enough to me looking at another C mount camera I have here.

It's the engineering of an adapter which is going to be tricky and it would be an expensive mistake if it didn't work.

I do feel the optics of the Metabones reducers are worth the money and could give excellent results if we could get one to fit. I've emailed them to ask if they think it's possible, so let's see if I get a response.

Looking at lens options generally, I'm also looking at Kowa C-mount lenses as there are a few Blackmagic camera owners using them and they have a good reputation for quality. There are plenty of old C-Mount lenses around on ebay but I suspect quite a few of them are not worth bothering with.

Sorchey

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Re: Let's talk LENSES!
« Reply #24 on: November 08, 2017, 07:32:04 AM »
Hey everyone!


First of all, I really don't know much about lenses.

I've purchased this lens (http://www.krontech.ca/store.html#!/Fujian-25mm-f-1-4-C-Mount-lens/p/77244591/category=21981409) in an online auction similar to ebay, since it was really cheap and had some good reviews. After arriving today I wanted to try it out, but I couldn't get the mounted lens to focus at all. I have the feeling that the lens is malfunctioning, but maybe one of you can give me some tips.

If I unscrew the lens and simply hold it in front in a distance of about 2-3mm, I get a sharp image. But even then, turning the focus ring doesn't seem to change much.

In general: Is a spacer ring needed for this lens?

tesla500

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Re: Let's talk LENSES!
« Reply #25 on: November 08, 2017, 11:39:11 AM »
Hey everyone!


First of all, I really don't know much about lenses.

I've purchased this lens (http://www.krontech.ca/store.html#!/Fujian-25mm-f-1-4-C-Mount-lens/p/77244591/category=21981409) in an online auction similar to ebay, since it was really cheap and had some good reviews. After arriving today I wanted to try it out, but I couldn't get the mounted lens to focus at all. I have the feeling that the lens is malfunctioning, but maybe one of you can give me some tips.

If I unscrew the lens and simply hold it in front in a distance of about 2-3mm, I get a sharp image. But even then, turning the focus ring doesn't seem to change much.

In general: Is a spacer ring needed for this lens?

A CS-C ring is required for this lens, yes.

Martin

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Re: Let's talk LENSES!
« Reply #26 on: December 18, 2017, 04:11:58 PM »
Greetings fellow time travelers,

I think this belongs here, came up again in a PM this evening.
I found this way back, when I was still waiting for the Chronos to arrive and researching native lenses:

http://www.ebay.de/itm/142138567245?orig_cvip=true

It's an f/0.7 C-Mount 50mm lens by Fujinon.

IIRC that's very close to the "practical" limit. It was too expensive to just "shop and test" it..
It "could" have been incompatible (I heard about some c-mount lenses lenses which won't work on the Chronos, don't remember the specifics. Protrusion issue into the camera body? See image 5 for example..).
AND notice the lovely "-TV" tag. Would've been too risky ;)
(It may have been vastly overprized as well.)

Here's some explanation why you won't find much faster lenses:
https://www.youtube.com/watch?v=84ZXfviMBFE

And this was just a marketing stunt without actually producing anything usable:
https://petapixel.com/2013/08/06/carl-zeiss-super-q-gigantar-40mm-f0-33-the-fastest-lens-ever-made/

;D

All the best
Martin

Nikon1

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Re: Let's talk LENSES!
« Reply #27 on: February 27, 2018, 05:23:43 AM »
Greetings fellow time travelers,

I think this belongs here, came up again in a PM this evening.
I found this way back, when I was still waiting for the Chronos to arrive and researching native lenses:

http://www.ebay.de/itm/142138567245?orig_cvip=true

It's an f/0.7 C-Mount 50mm lens by Fujinon.

IIRC that's very close to the "practical" limit. It was too expensive to just "shop and test" it..
It "could" have been incompatible (I heard about some c-mount lenses lenses which won't work on the Chronos, don't remember the specifics. Protrusion issue into the camera body? See image 5 for example..).
AND notice the lovely "-TV" tag. Would've been too risky ;)
(It may have been vastly overprized as well.)

Here's some explanation why you won't find much faster lenses:
https://www.youtube.com/watch?v=84ZXfviMBFE

And this was just a marketing stunt without actually producing anything usable:
https://petapixel.com/2013/08/06/carl-zeiss-super-q-gigantar-40mm-f0-33-the-fastest-lens-ever-made/

;D

All the best
Martin

I own a Set of Schneider-Kreuznach Xenons, 17mm, 25mm and 50mm
All of them are quite fast and have a f/0.95 Aperture and are native C-Mount.
The 17mm is built for 2/3", but almost covers the Nikon1 Sensor. It also prodtrudes extremely far into the Camera Body, and i had to do some extreme Modifications to my Nikon J5 to make it fit.
The 25mm ist for 1" but mostly covers MFT.
The 50mm is not exactly known for what Format it is built, but covers FullFrame with some Modifications.
I would realy recommend, if anyone want to buy such a Lens, to do some proper Research about those old Lenses and the Images they produce and maybe try them on Location when buying if that is possible.
Because some (or even most) of those old, extreme fast Lenses can produce quite some funky Results you might not like.
I realy like the Look those Lenses make, but that is up to personal taste.
That said, i also keep a set of more modern, (not quite as) fast Lenses for every Focal Length, in case i need Images with a "Cleaner" Look or for realy difficult Light situations, if i dont want Flares and all that stuff.
.
Also keep in Mind:
f/0,7 is just one full Stop more Light than f/0,95. And f0,95 is again just one full Stop faster than f/1,4.
That means your 50mm 1.8 or 1.4 is plenty of a fast Lens for its commonly cheap price.
You can get something like a SMC-M PK 50mm f/1.7 for like 20 or even less, if you spend some time searching the internet.
That is a realy sharp and reasonably fast Lens.
And compared to the Prices for your average f/0,95 (or faster) Lens that is just no Question what to get, unless you realy know what for and why you would need those Ultra-Fast Lenses.
Mostly it is just easyer to add Light to whatever you are filming.
Or just use Sunlight +maybe Reflectors & Diffusors, if that is a Option.
.
Depends on what you want capture, it may realy be possible you find yourself someday in a situation, where you cant just add Light and also cant use other camera settings for technical (or other) Reasons, like Framerate and Distance or the scale of your Shot.
Even then those Lenses Wide open can completely "destroy" your image in terms of contrast and so on.
So you will find yourself sometimes maybe even stopping those down slightly to like f/1.4 or f/2 (or even further) if you want to use it for someting else than cinematic images. Technical Imaging for example.
And then you could just use any other Lens as fast as f/1.4 or f/2
.
I have to say those Schneider-Kreuznach Xenon Lenses are Realy sharp, even wide open. Maybe some of the sharpest 0,95s you will get, especialy considering the Age of those.
BUT they loose a Lot of Contrast when wide open, make Flares and quirky bokeh, and some other stuff. And i REALY like that.
Not all of those old superfast Lenses are Sharp Wide open!!! So at least get some high Quality Test images or references of People, that used those Same Lenses you want to buy.
.
And i have to say, i allready find that 50mm f/0,95 Lens Stupid Hard to focus, because of how shallow the Focal plane is.
I never got into the joy of playing with faster glass (that had a proper Mount and could focus to infinity) yet, but i would be realy curios, what it would be like to use & focus those even Faster Lenses.
I am realy used to manual Focusing, but that Lens may be the Hardest one to properly Focus, out of those that i own.
.
.
.
.
SUMMARY: Know what you are doing if you buy Lenses like this, because Stuff is expensive.

baseballcam

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Re: Let's talk LENSES!
« Reply #28 on: March 27, 2018, 11:49:12 AM »
hello fellow time travelers,

looking to shoot some baseball games, maybe the pitcher, from far away (maybe 120-150 feet). Looking for a compatible lens for the chronos but having a hard time purchasing with any confidence.

if anyone can offer any recommendations it would be greatly appreciated

Nikon1

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Re: Let's talk LENSES!
« Reply #29 on: October 13, 2018, 01:57:56 PM »
https://www.ebay.de/itm/ERNITEC-Auto-Iris-Lens-f1-3-5-6mm-2-3-25mm-Gewinde-/232904148794
.
Here is an very wide Lens for an reasonable Price for anyone searching for one.
CS-Mount, so no Distance Ring required.
Lens is auto-Iris so you propably cant change aperture on the go and most likely will need to use it wide open all the time.