lens advice

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hywel1984
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lens advice

Post by hywel1984 » 09 Nov 2014, 13:17

Could anyone tell me which lens would be better for an E700 spotter build. The smaller lens is a c mount CCTV f1.4 lens and the larger one is a 50mm m42 f1.8 lens
Thanks very much
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Last edited by hywel1984 on 09 Nov 2014, 19:19, edited 1 time in total.

Jirka
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Re: lens advice

Post by Jirka » 09 Nov 2014, 16:35

Take the smaller one. It is faster and built for similar or identical sensor size. The larger lets (almost twice) less light in and projects most of it to outside of the sensor.

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Torchwood
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Re: lens advice

Post by Torchwood » 09 Nov 2014, 16:52

What is focal lenght on the smaller lens? I guess 25mm . If it's a 25mm 1.4 lens. It's too wide to be a good use for a spotter, I prefer at least 35mm around 2x magnification to be a happy medium. 50mm will give you a good magnification around 3.5x.
M42 lens will work well with a adaptor, but it's bulkier and heavier than c mount lenses.
Toni
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some bloke
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Re: lens advice

Post by some bloke » 09 Nov 2014, 17:47

Torchwood wrote:What is focal lenght on the smaller lens? I guess 25mm .
If it's a 25mm 1.4 lens. It's too wide to be a good use for a spotter,
I prefer at least 35mm around 2x magnification to be a happy medium.
50mm will give you a good magnification around 3.5x.
M42 lens will work well with a adaptor, but it's bulkier and heavier than c mount lenses.
Toni
As above.

Despite some of the light falling off the sensor what does hit it is very loud and proud, and evenly distributed because of the massive glass elements.

If however you are not able to expose all of the sensor to all of the SLR's 1" exit glass, and are budget minded enough to accept second best then a C mount
35mm or 50mm lens with smaller exit glass would get more of what it sees to an unobstructed sensor if the camera has a C or CS mount thread adaptor - or a Watec camera.

S mount adaptors are made for much narrower CCTV lenses, which are pants for low light spotting and need stacks of illumination as a last ditch bargain basement solution.
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hywel1984
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Re: lens advice

Post by hywel1984 » 09 Nov 2014, 18:15

The small lens is 50mm.
Some bloke your really not a fan of s mount adapters are you. I can see where your coming from as they screw into the housing of the e700 and are bound to cut out a small amount of light but if your using it with an illuminator surely its going to negligable? Do you think it's better to take the camera out of its housing all together and cut a 1" hole in the project box to fix a c mount adapter directly into the box and mount the camera behind that?

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some bloke
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Re: lens advice

Post by some bloke » 09 Nov 2014, 18:37

hywel1984 wrote:The small lens is 50mm.
Some bloke your really not a fan of s mount adapters are you.
I can see where your coming from as they screw into the housing of the e700 and are bound to cut out a small amount of light
but if your using it with an illuminator surely its going to negligable?
Do you think it's better to take the camera out of its housing all together and
cut a 1" hole in the project box to fix a c mount adapter directly into the box and mount the camera behind that?

Nope - it's shit solution with shit results for those who can grasp the difference:
I've Been there and done the long range/shadows comparisons.
If you are happy enough to focus IR light into night adjusted nocturnal quarry eyes when you can avoid it then go ahead with a so-so results choice.

Here is a light read of what happens when IR is used:
http://www.dcnr.state.pa.us/wrcp/wildno ... 20108.html

A C mount adaptor is the ideal medium to achieve the near ultimate spotter performance - pardon the pun. :D
But that will not fit to a KTC camera without a lot of specialist effort.
As you know, I make something even more suitable but it is an expensive process.

If that is a Chinese C mount lens I doubt it will give F:1.4 performance but it will be much better than CCTV lenses. which have very small glass and apertures
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Torchwood
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Re: lens advice

Post by Torchwood » 09 Nov 2014, 19:06

I was comparing few lenses last week, on the spotter I had a chinon 55mm 1.7. Which I rated quite high optically. I had my 50mm 1.4 lens on loan earlier but that night it was back and I put it on the potter. It was many times brighter than m42 55mm. I could easily spot over 200m. Eye shine over 250m.

The spotter was made with a cheap effio box camera, with a m12 to c mount adaptor, while I had the m42 on, I always blamed the camera for not giving a clear image, but that night both lens and the camera operated flawlessly.

Toni
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some bloke
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Re: lens advice

Post by some bloke » 09 Nov 2014, 19:15

Hywell, could you edit your first post for us and put a space between the second and third image links so we can read the page better?

Toni - was that while using an illuminator?
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hywel1984
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Re: lens advice

Post by hywel1984 » 09 Nov 2014, 19:29

What about this adapter if I drill the hole larger to fit the e700 lens housing through

http://www.ebay.co.uk/itm/111237741748? ... EBIDX%3AIT

Or this adapter fitted directly into the project box with the camera out of its housing fitted behind it?

http://www.ebay.co.uk/itm/330988662695? ... EBIDX%3AIT

Would you think these would give significantly better performance than this adapter that I'm currently using?

http://www.ebay.co.uk/itm/121202643148? ... EBIDX%3AIT

Thanks for the help
Last edited by hywel1984 on 09 Nov 2014, 19:57, edited 1 time in total.

Snapper
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Re: lens advice

Post by Snapper » 09 Nov 2014, 19:32

Some bloke, I can't comment on your experiences with different lenses but I just think I ought to clarify one point. The f number is a ratio between focal length and entrance pupil so really the exit pupil should have nothing to do with how much 'light' hits the sensor. There is no theoretical reason why an s, c, cs or SLR lens that share the same aperture cannot give the same results - there is of course a difference between lens quality and their ability to transmit visible and IR 'light' so that it likely to be much more important than lens size or mount type. There will be c mount lenses that perform better than m42 lenses and visa versa so it is difficult to say which is better on mount type alone.

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