IP CAMERA LEARNING & RESOURCE CENTER

It can be quite a challenge to find a suitable lens for megapixel cameras. It seems that the technology in an average IP camera progresses at a much faster rate than lens manufacture. After all, crafting lenses is a highly skilled industry with very traditional roots while the electronics industry tends to move faster than a freight train.

So when we heard that Axis had began to replace the lens that ships with their popular 211M camera with a brand new megapixel lens to improve picture quality, we had to take a look. Any improvement in megapixel image quality is very welcome and of great benefit to the IP CCTV industry.

Lens

The new lens that ships with the Axis 211M is a Tamron Lens. Unlike the Pentax lens before it the new lens is suitable for megapixel cameras. It has almost the same specification as the previous lens: 3-8mm varifocal DC-iris, F1.0 and a viewing angle of 37 degrees (tele) – 93 degrees (wide). The new lens is also 15mm longer but should still fit into any standard housing without any difficulty.

Ease of use

The lens I received was pre-focused but not at it’s widest position. First impressions were good:

Axis 211M - New lens – Default settings (640×480 VGA – 30% compression)

Adjusting the lens was simple. First we disabled the DC-iris to allow the maximum level of light through to aid focussing. Then we zoomed out the lens to its widest position and refocused before re-enabling the DC-iris. The process was quite simple and easy to do with the new lens.

Performance

To compare I set up two Axis 211M IP cameras. An old model with the Pentax lens and a new model with the megapixel Tamron lens. Both cameras were installed indoors behind a glass window.

When comparison shots were taken the settings in each camera were identical and we tried to allow for the same amount of light in each shot. Snapshots from both cameras were saved and the results are as follows:

Axis 211M – New Lens, wide 94 degree horizontal – (640×480 - 30% compression)

Axis 211M – Old Lens, wide 94 degree horizontal – (640×480 - 30% compression)

In terms of color and color reproduction we would say the results shows more dynamic range to the palette, the depth of the colors is richer and more natural than the previous lens while the image produced by the old lens seems to be misty and not as rich.

Resolution is definitely clearer in the new megapixel lens providing a sharper, more clearly defined image.

As with all cameras, the amount of light captured by the image has a large effect on the overall image quality. Too little and the image will be grainy and less detailed, too much and it will underexpose key elements of the scene. In the Axis 211M, exposure control is limited to “Automatic, hold current, Flicker-free 50Hz and Flicker-free 60Hz”. This doesn’t give room for fine adjustment of your exposure so attention must be paid when installing the camera. Place the camera ideally in a spot where the sun will be behind it and try not to capture too much sky in the image. Of course if you zoom the lens in this will also reduce the amount of light which passes through to the sensor.

Comparison with similar models on the market

Mobotix M22M-SEC-D22

Mobotix M22M-SEC with D22 90 degree lens

The Mobotix M22M-SEC can be considered as a direct competitor to the Axis 211M. When we compare images, the result doesn’t look as sharp as the Axis 211M and the colors are much more muted. There is a good range of depth to the colors though; the dark colors appear slightly darker on the Mobotix camera, they are just not as vibrant. Of course I cannot match exact camera settings using a different model of camera.

Axis 233D

Axis 233D (768 x 576 - 30% compression)

Axis’ high-end PTZ dome camera really suffers in terms of sharpness due to its non-megapixel resolution and the colors are not as vibrant or realistic giving similar reproduction as a Mobotix camera.

Overall

In summary we would say that adding a true megapixel lens to a megapixel camera does provide tangible benefits in terms of picture quality and colour reproduction. The new lens improves resolution, sharpness, color depth and reproduction. Importantly though, increasing the image quality and detail seriously improves identification of people and objects in a scene which is the main reason why we consider megapixel cameras in the first place.

Ideal for security applications, for both indoor and outdoor use, we have no problem recommending the Axis 211M for anyone’s IP CCTV needs.