Hints and Tips

Why back focus?

When the lighting level falls, the auto iris opens and the depth of field changes. This can be seen when cameras that are in focus during good lighting conditions tend to "defocus" when the light level falls. It is very simple problem to solve - always install the camera using a "Neu- tral Density (ND) filter". Placing these filters in front of the lens simu- lates conditions at very low light levels, such as dawn and dusk, this will allow for the correct setting of focus and back focus. The objective is to open the lens iris to its maximum. The grading of ND filter will vary depending on the ambient light - on a very bright sunny day you will need a larger ND filter (number) than on a cloudy overcast day. To select the correct ND filter, place it over the lens until you can just see the picture but are able to focus clearly.

Manual and fixed iris lenses

1.Set the camera to an object at a point in the distance (the target will appear very small on the monitor).

2.If the lens has a focus ring, set this to infinity.

3.Adjust the lens iris to the widest opening then place the appropriate ND over the lenses to simulate the low light.

4.Adjust the camera focus to achieve the sharpest (clearest) picture.

5.Remove the filter.

Focusing a fixed auto iris lens

1.Set the camera to an object at a point in the distance (the target will appear very small on the monitor).

2If the lens has a focus ring, set this to infinity.

3.Adjust the lens iris to the widest opening. This is best done by pla- cing the appropriate ND filter over the lenses to simulate the low light, which will naturally force the iris open.

4.Adjust the camera focus to achieve the sharpest (clearest) picture.

5.Adjust the Level and ALC controls on the lens for best performance.

6.Remove the ND filter.

Using International Protection (IP) ratings

IP rating is used in this catalogue for defining the weatherproof stan- dard of CCTV products. This is mainly for outdoor products of prime importance. The following table shows the definition of the interna- tional protection ratings and helps you to select the proper equipment for your application.

First number: Protection against solid objects

0 = No protection

1 = Protected from solid objects up to 50 mm (e.g. accidental touch by hands)

2 = Protected from solid objects up to 12 mm (e.g. fingers)

3 = Protected from solid objects more than 2.5 mm (e.g. tools and small wires)

4 = Protected from solid objects more than 1 mm (e.g. small wires)

5 = Protected from dust; limited entrance (no harmful deposit)

6 = Totally protected from dust

Example: IP67 rated product:

The first number is the protection against solid objects:

6 = Totally protected from dust

The second number is the protection against liquids:

7 = Protected from the effects of immersion between 15 cm and 1 m

Focusing a zoom lens

1.Place the appropriate ND filter over the lens, this will force the iris open.

2.Set the focusing ring to "far" or wide angle.

3.Aim the camera at an object approximately 30-50 metres away. The object appears very small on the monitor.

4.Adjust the camera focus for maximum clarity.

5.Zoom the lens to an object nearby (close up).

6.Set the lens focus for maximum clarity.

7.Remove the ND filter. It should now be possible to zoom in and out over the field of view maintaining good focus.

Cleaning of lenses & CCD

Proper cleaning procedures will minimise the amount of time it takes to clean the surfaces of the lens and CCD imager. To clean the front and rear surfaces of the lens,

1.Detach the lens from the camera.

2.Before rubbing the surface area of either the lens or the CCD ima- ger, blow any loose particles using a pressurized "air duster". (can be purchased from photographic supply dealers)

3.Apply a minimum amount of alcohol to clean the surface areas of both the lens and the CCD imager, via a cotton swab. (recommended solvents would include 89-91% ETHANOL, or PROPANOL with a resi- due value after evaporation of maximum 0.001%).

4.Rub lightly with a dry cotton swab after evaporation Blow again with the "air-duster" to remove remaining dirt or dust particles.

Do not use acetone, as this destroys plastic materials.

Second number: Protection against liquids

 

0

= No protection

 

1 = Protected from vertically-falling drops of water (e.g. condensation)

 

2

= Protected from direct sprays of water up to 15° from vertical

 

3

= Protected from direct sprays of water up to 60° from vertical

 

4 = Protected from water sprayed from all directions; limited entrance

 

allowed

 

5

= Protected from low pressure jets of water from all directions;

 

limited entrance allowed

15

6

= Protected from strong jets of water (e.g. for use on ship decks);

limited entrance allowed

 

7

= Protected from the effects of immersion between 15 cm and 1 m

 

8

= Protected from extended periods of immersion under pressure

 

Example: IP41 rated product:

The first number is the protection against solid objects:

4 = Protected from solid objects more than 1 mm (e.g. small wires) The second number ist the protection against liquids:

1 = Protected from vertically-falling drops of water (e.g. condensation)

© Siemens Building Technologies Group

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Siemens CRT, TFT manual Why back focus?, Manual and fixed iris lenses, Focusing a fixed auto iris lens, Focusing a zoom lens

CRT, TFT specifications

Siemens, a prominent name in electronics and engineering, has made significant contributions to display technology, particularly in the realms of Thin Film Transistor (TFT) and Cathode Ray Tube (CRT) displays. These technologies have paved the way for advancements in visual media, ranging from television sets to computer monitors.

TFT display technology, a type of LCD (Liquid Crystal Display), employs thin film transistors to produce brighter and more vibrant images. One of the main features of TFT displays is their ability to deliver high resolution and excellent color reproduction, making them ideal for various applications such as smartphones, tablets, and laptops. TFT screens utilize an active matrix approach, which allows each pixel to be controlled individually. This method results in faster response times and improved image quality, with less motion blur, compared to older passive matrix displays.

One of the key characteristics of TFT technology is its versatility in different settings. It supports a wide range of viewing angles, which enhances the user experience whether one is viewing the display head-on or at an angle. Additionally, TFT displays are known for their thin profile and lightweight design, contributing to the overall portability of devices that incorporate them.

On the other hand, CRT technology, which was once the standard for televisions and computer monitors, uses electron beams and phosphorescent screens to produce images. One of the defining features of CRTs is their ability to display deep blacks and a wide color gamut. CRT technology can achieve high refresh rates, reducing flicker and improving the quality of fast-paced visuals. However, CRTs tend to be bulkier and heavier than modern display technologies like TFT.

Despite the evolution towards flat-panel displays, CRT technology is still appreciated for its natural color and motion portrayal. Siemens has leveraged these characteristics to produce quality CRT monitors that were favored in professional settings, including graphic design and medical imaging, where color accuracy is paramount.

In summary, Siemens has played a vital role in advancing both TFT and CRT technologies. TFT displays are recognized for their high resolution, fast response times, and design versatility, while CRTs are celebrated for their rich color and depth. As technology continues to advance, the legacy of these display types remains influential in shaping modern electronic devices.