focus grief KP&C-350BH camera Fujinon YV5x2.7R4B-SA2L

[sparrow 0]

I purchased these items from Spytown and cannot seem to get it to focus except in extreme telephoto range. Camera has two switches on the back which I have set for ALC and DC. Lens has a wide/tele slider and a near/far focus. I can almost get it to focus in wide angle but focus ring stops just short of good focus. If I adjust for telephoto range I can get a perfect focus but only at one point.

 

Lens is Auto iris and I plugged the connector into the back of the camera.

 

I have not attempted to adjust the trim screw labeled DC Level as I wanted input from this forum first.

 

What the heck am I doing wrong or is something defective?

[Marrkk 0]

I don't know that particular camera, but If it is a CS mount lens and a camera designed for a CS mount, then you probably have to adjust the camera's backplane. Look at your camera instructions. I believe the normal process with a vari-focus lens is to put both the focus ring and the zoom ring at about their mid-point (in the middle of their range) then adjust the backplane until you get close to focus. Then do your final adjustments. If you have a C-mount lens with a CS-mount camera, you need an adapter (but I doubt Spytown would sell you both on one order without indicating to you the need for the adapter). Call the Camera company's technical support. With a new camera, they should walk you through the solution to this type of problem (I doubt it's a lens issue)

 

Good Luck!

[Cooperman 0]

If you need to set up the back focus on any camera:-

 

1) Set the lens focus ring to infinity and point the camera at a very distant object.

2) Set the iris to maximum aperture (use a filter to reduce the light transmission through the lens sufficiently that you can see at the very least the shadow areas [i.e. the dark bits!!]).

3) If a Varifocal or Zoom lens is fitted always set the focal length adjuster ring to maximum telephoto.

4) Adjust the back focus until a sharp image is displayed, then adjust the iris control (without the filter fitted) to achieve the desired level of exposure.

 

It should then be possible to manually focus the lens on objects at any distance, and focal length setting.

 

If you can't focus the lens using the method above, then it may be a C / CS mount issue, in which case, either fit a 5mm spacer ring behind the C mount lens, or if you don't have a spacer ring, gently unscrew the lens (with the camera and lens in a darkened environment) then manually move the lens away from the mount a few millimetres and you should begin to see a sharp image appear. If that happens, go and get a spacer ring!!

 

Nowadays it's almost unheard of for a CS mount lens to be fitted onto a C mount camera; if you try it, it just ain't gonna work!!

[spytown 0]

since this topic comes up often in this forum..i thought i would say a few words on HOW TO BACK FOCUS A VARIFOCAL LENS

 

Back focusing a lens to a camera that it's attached to is critical in obtaining optimum clarity. With a fixed lens it's quite basic since the focal length is "pre-set." The varifocal lens, having numerous focal length settings, poses the question: Where do I begin?

 

The very first thing you must know to obtain proper back focus is the minimum object distance (MOD). Let's use the 1/3-inch varifocal lens for this example. Most 1/3-inch varifocal lens manufacturers show an MOD of 0.3 meters or approximately one foot for this lens. Now, attach the varifocal to the camera and set the three barrels as follows:

 

Focus Barrel. Move completely to the "near" setting, opposite of "infinity" or "far." You also should notice the front lens element moves forward, away from the front of the camera.

 

Focal Length Barrel. Move completely to the wide "W" setting, the opposite end of the telephoto or "T" setting.

 

Iris Barrel. With the camera on and viewing the monitor, achieve the optimum lighting condition without washing out the picture by moving the barrel from close towards open.

 

Now put a "test pattern" or any white paper with either print or an image on it at the one-foot point from the lens. Fill the entire screen of the monitor with this "test pattern" and begin adjustment. This "adjustment" varies with camera manufacturers. Some allow you to move the CCD of the camera by way of a screwdriver placed inside a hole of the camera body. Others use a collar with the lens screwed into this collar further in or out of the camera to set the lens in relation to the CCD of the camera.

 

In either case, adjust the position to achieve optimum clarity on the monitor. Once achieved, lock this position of the lens to the CCD distance. Now remove the "test pattern." and change the focal length barrel of the lens to any position, then adjust the focus barrel to get optimum clarity. Remember, a varifocal lens means that anytime you adjust focal length, you also must adjust focus.

[Cooperman 0]

I'm just curious spytown, but the method you've suggested for adjusting the back focus, is this a general North American technique, or perhaps something you just do yourself?

 

No disrespect intended, but with almost thirty years experience of setting up cameras, this is the first time I've ever heard of anyone attempting to fix a critical setting (back focus) using a variable (the lens Minimum Object Distance), when a fixed reference point (infinity) is the same the world over.

 

With some lenses, the Minimum Object Distance can actually vary between units in a production batch, much less different models.

 

Also unless the iris is opened fully, the increased depth of field caused by even slightly stopping it down, means the back focus point could be anywhere within the DoF range, and that's obviously not the point of the exercise.

[cctv_down_under 0]

I am betting the answer to the guys question is that he has the ring either on the end of the lens by mistake or on the camera by mistake, some dodgy suppliers still ship lenses and cameras with the spacer in place.. also you may be using a 1/2" camera and the wrong lens format for it?

[spytown 0]

cooperman..that follows textbook on proper backfocus adjustment.

[Cooperman 0]

Just because it's in a textbook, doesn't necessarily mean it's either appropriate or correct. It may be an opinion and it may possibly work, but that doesn't mean there isn't a better way of doing it.

 

The whole point of setting a correct back focus point, apart from the issue of allowing the original lens to produce a sharp image on the focal plane, is that when changing lenses or for example altering the focal length on a zoom optic, you should be able to achieve a focussable image without having to readjust the back focus again.

 

In fact, if you focus a zoom lens at maximum telephoto setting and then change it to wide angle setting, the image should remain sharp if the back focus has been set correctly (and it's obviously a half decent lens!). Try and do that the other way around, and the image will almost certainly go out of focus as you move towards telephoto.

 

If an engineer does not have access to the Minimum Object Distance for a given optic (which of course varies from one lens design to another) , or there is a variation within a batch production, or the iris is set to anything other than maximum aperture, it just ain't gonna produce the desired result.

 

We can do an awful lot with modern equipment, but we can't change the laws of physics.

[rory 0]

i got a question, what do you guys do when focusing a camera outside in sunny tropical conditions ..

[Cooperman 0]

Sunny tropical conditions ..... in the U.K.? .....

 

Seriously rory, we do get fairly intense sun mid summer (contrary to popular myths), and my favoured option for adjusting cameras is to use two polarising filters, one on top of the other, held over the front of the lens.

 

As you rotate one filter, you can vary the degree of "Neutral Density" filtering from absolute minimal to almost total blackout.

 

Of course it's not really a neutral density set up, but it has exactly the same effect, and under any given lighting conditions, you can infinitely vary the filtration to achieve a correctly exposed image.

[CCTVmofo 0]

Check out this link to fact check Spytown:

 

http://www.tekstaroptical.com/faq.html

 

This is where he got the instructions on Back Focusing.

 

In the future, you should be more up front and site your resources. It is more helpful to everyone in this forum to just point out the site instead of trying to take the information as your own.

 

In this case, you would have done a better service by just forwarding us to the original site which actually has a lot of useful tips and tricks.

 

Something to consider...

[rory 0]

well coop im waiting for an overcast day, cause there's only 30 minutes of low light before it gets dark and since its winter now the darn sun is going down looking right at the cameras ..argghhh ..

 

Actually what i did anyway was use a sweatshirt to cover the monitor and my head as i adjusted it (on the 12' ladder with my 13" TV) .. came out good .. though still too sunny to normally do a perfect job, i think i aced it this time .. my main concern today was in th sunlight anyway, to adjust the iris pot. Now ill wait for an overcast day ... hopefully that will be tomorrow .. If not i got 30 minutes of low light before its too dark, to focus 8 cameras all up on poles and a good distance between them all ..

 

BTW i did the normal back light adjustment (without the filter cause i cant get one down here) and yeah i did it the coop way, as thats actually the way I always did it before ..

 

EDIT - had to go back and focus the bad boys in the low light after all

Plus wait around to do the UF500's in the pitch dark again ... darn it was cold ..

[Cooperman 0]

Thanks for the link CCTVmofo;

I had a quick look and there are a few things there which are, shall we say, less than accurate, but I won't hold that against them. IMHO most of the information is very good (but not all).

 

Strewth rory, a 13" TV up a 12' ladder!! I used to use a 9" B/W monitor myself, because we didn't have any small test monitors in those days.

 

One thing you could try - I'm assuming you won't find it easy to get hold of an anti glare filter (you can get some reasonable ones for computer VDU's), maybe check out whether you can get a lightweight slatted wooden louvre. You only need to see small patches of screen to correctly focus, and picture quality always looks different when you see it on a monitor in a darkened room, but it might be worth a try.

 

Incidentally, when focussing cameras (during the day) being used with tungsten IR lamps, I used to remove the filter part of the illuminator, and hold that over the front of the lens to allow re-focussing at the correct light frequency. 850nM is the same whether it's filtered from the sun or a tungsten bulb. Of course the quantity of light will differ, and you have to realign illuminators (at night) for correct night operation, but usually the focussing can be done during the day.

 

Now admittedly, I have a set of IR filters between 800 and 1000nM, but they rarely get used these days.

 

Take care up that ladder rory!

[rory 0]

so Coop its best to backfocus in telephoto rather than wide angle correct?

 

I would imagine as you can focus better when zoomed in on something close to the furthest focal lenth of a lens .. i mean i just did it so thats why im saying, i tried it wide angle but cant see everything as clear, so did it in telephoto and was much easier. Both stayed in focus in wide angle and in telephoto ... not inbetween though ofcourse ..

 

I need a darker tinted glass though, anyway, its low light from overcast now so ..

 

Rory

[Cooperman 0]

Absolutely rory!

 

When you're using a zoom or varifocal lens, if you try and set the back focus at wide angle, the depth of field is much greater than at the telephoto setting, so it's significantly more difficult to find the optimum 'point of focus'.

 

If you set the back focus at telephoto (with the lens focussed at infinity and pointing at a distant object), when you change to a wide angle setting the depth of field increases, so there is a better than reasonable chance that with a quality lens, the image will remain sharp throughout the zoom range.

 

You don't need a correctly exposed image to focus a lens, just so long as you can see the shadow components, it doesn't matter if the highlights white out completely (although excessive flaring with cheap optics can make the job even more difficult).

 

To be honest, it's very easy to get hung up on the 'back focus' issue, where in reality, it's rarely as crucial as we might at first think.

 

If a box camera is going to be fixed in position fitted with a single (non motorised) lens, once that image is correctly focussed it's unlikely to be changed unless the camera is subsequently redployed elsewhere. As long as the image is correctly focussed, that is really the most important thing.

 

From a professional perspective, I always wanted my cameras to be set up correctly, so that if any subsequent installers decide to move it, or fit alternative lenses, it will work first time for them, and they won't be cursing the useless individual who couldn't even get the back focus set correctly

 

It takes less than 60 seconds to set a back focus, so I don't begrudge spending the time to get it right.

 

It's worth remembering, you can always set the back focus using a preferred 'benchmark' lens, preferably a very high quality fixed focal length optic (perhaps a 16 /25 / 50mm), and then any other quality lens can be fitted and it should work correctly without any further readjustment. If you use a manual iris lens (set to maximum aperture) with the cameras 'Electronic Iris' function switched on, then adjusting the correct back focus is a piece of cake.

 

One other quick point; with very cheap and nasty lenses, the back focal point can even vary between lenses of the same batch!

[rory 0]

Yep, anwyay that didnt last, wasnt really in focus ... in wide angle anyway, okay whats the best lighting condition to back focus in, without a filter, since i cant even get a darn tinted piece of glass down here ... also, i have a 50-50mm Computar lens im working with ..

 

PS. I dont think i really ever had to back focus any of the other ones ..

 

I have to do this indoors .. anyway, im not too worried about whether I have to refocus it if i zoom it in .. which i have to anyway .. im doing it in my appt which is only 20' long so i need to do this in wide angle now .. so far it is a great focus once i adjust it in some like 12mm ... waqs having issues for a bit there where only parts of the image was getting focused, had to pull the lens off and replace it again and power on off etc, then it came back to normal ..

 

I back focused in low light, where only 1 light in the hall was on .. focused it in the same light, when i turn the light on its clear ...and when i turn it off it stays clear .. obviously not 'as' clear as its lower lighting .. but the writing i was using to focus on stays clear.

 

I got some more time to play with it .. but anyway, any tips on setting the Iris pot level? That part also is messing me up .. Should i just do it indoors with the lights on .. or does it have to be done outdoors ..?

 

thanks

Rory

[Cooperman 0]

Ideally, setting a back focus in the least amount of usable light is the perfect situation, then you don't have to worry about ND filtering, you just have to put up with on screen noise the size of golf balls

 

Most manufacturers back focus their cameras before delivery, so it's usually only an issue with odd or exotic lenses.

 

The other way of approaching the subject is where (for example) you want to focus on an object about 30 feet (10 metres) away. Twist the lens focus ring slightly away from infinity (if it's marked up, then obviously leave it set to a point approximating 30 feet), then use the back focus adjuster to move the imager until the image is in sharp focus.

 

If the camera is being used for a fixed view indoors, then this "alternative" method works just as well.

 

Setting an iris pot, is light level (not location) dependent. If you have a very well lit room, adjust the pot slowly from maximum aperture until the image is correctly exposed. Then turn the pot perhaps a further 5 > 10 degrees, and that will still maintain correct operation, but allow for a small amount of tolerance under varying circuit temperatures. Personally, I always like to set cameras up when they're running at normal operating temperatures (if you set it up 60 seconds after power up from cold, it may well drift a few hours later, particularly if it's being used in a very warm environment).

 

Also, if the camera is eventually being installed near a ceiling, the temperature can rise quite dramatically above that found on a test bench, and that can cause circuits to drift.

 

If you shine a torch directly down the lens (or point the camera at the ceiling and move it slowly until the light source drifts into view), the iris should then shut down correctly, and reopen again as the light moves out of the field of view.

 

No matter how well you set up a camera on a bench / in a lab / on site, you still have to double check that it's operating correctly when it's finally installed 'in situ'.

[rory 0]

Anywayz, so in bright sunlight for backfocusing or regular focusing, should use the NF or a PF? Would it be fare to say use a NF for back focus at Infinity, and a PF for general focusing? And i take the level of the NF will depend on the amount of light at the time? Whats good for Bright sunlight, and then overcast, 0.5?

 

Rory

[Cooperman 0]

Neutral Density Filters are normally sold by photographic dealers in graded steps, so for example NDx2, NDx4, NDx8 (x2 is equivalent to one 'f' stop on a lens).

 

For focus setting in very bright light, you normally need a very dense level of ND filtering, so (for example) with a set of 3 filters, you can combine them to create anything from NDx2 > NDx14.

 

With two polarising filters, you simply rotate one over the other to create an infinitely variable level of filter density.

 

They work in different ways, but achieve similar effects, albeit there is a price differential, so you pays yer money and takes yer choice.

 

Personally I prefer the flexibility of using two polar filters, but each to their own.

[rory 0]

well i went to the only camera store here, took a 20 minute walk and 1 hour drive ... anyway, they dont sell filters, except for large lenses .. oh well ..

[Cooperman 0]

The filters don't have to fit ... you can simply hold them over the front (or tape them in place), while you make any adjustments.

 

Usually 52mm diameter or larger are ideal for this type of work.

[rory 0]

true, didnt think of that, though they probably want a fortune for them ..

 

im just going to order some from Tiffen after christmas ..

[Cooperman 0]

rory, you could always leave a stocking at the end of your bed on Christmas Eve

[rory 0]

yup, darn i gotta go back and focus this camera again at night .. at least in BW mode ... as when it got low light and switched to BW before the IR came on .. it was focused in color but not as focused in BW mode ... darnit .. i installed it in the day, and was just watching the playback over the internet,

[Cooperman 0]

Try using your 840nM dichroic filter. It's the same frequency of light day or night, so it's only the light level which will vary after dark.