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Rainer
May 4, 2007, 14:56:47
.. of different camera models

Hi,

I did take a look at the specs of The Imaging Source page and found following

DMK 21AF04 4 lx at 1/30s, gain 0 dB
DFK 21AF04 4 lx at 1/30s, gain 0 dB
DBK 21AF04 0.5 lx at 1/30s, gain 20 dB

Now an interesting value is that you specify the DFK as sensitive as the DMK.

DFK
http://www.theimagingsource.com/en/products/cameras/firewire_color/dfk21f04/specification/

DMK
http://www.theimagingsource.com/en/products/cameras/firewire_mono/dmk21f04/specification/

The DFK has a Bayer Matrix filter as well as a UV/IR cut filter and in the DMK the chip is naked ?

Can you tell me how do I calculate this so I can compare on the same basis ?

At first sight with 0.5 lux it looks like the DBK being a sensitivity wonder but then I look at gain 20db ?

So why do you not give comparable values ? e.g. measure the DBK also at gain 0 dB

Thanks in advance for your comments

saludos Rainer

profjohn
May 9, 2007, 18:34:11
Rainer,

Thanks you for the interesting comments on the sensitivity of our cameras.

(1) First of all, there seems to be a typo. I will ask our documentation department to take care of it asap.

(2) Unfortunately up to today there is no standardized method to measure the "sensitivity" of cameras.

Recently the EMVA (European Machine Vision Association) released a preliminary version of the first module of such a standard (please see the attached PDF).

The Imaging Source plans to specify its cameras based on this standard. However, the only way to compare cameras is to test them in the specific application context.

So, for the time being, we have to live with estimations. All industrial CCD cameras offer the same "sensitivity" regarding their basic premise, that is the "conversion from photons into electrons". As a rule of thumb we can assume that two "green photons" create one electron.

(3) Unfortunately, industrial customers (and up until recently, www.theimagingsource.com mainly addresses these customers) insist on having the "lx" parameter in camera spec lists. For these applications, the correct parameter specification is listed(i.e., gain = 20 dB):

DMK 0.05 lx
DFK 0.5 lx
DBK 0.3 lx

Rainer
May 9, 2007, 21:11:13
Hi,

Thank you. The problem is not the Lux definition but the fact that one camera was measured at 20dB gain and the other at 0dB.

The lx values you mention in your post more or less do coincide with the empirical measurements I have taken.

Rainer
May 9, 2007, 21:20:37
Recently the EMVA (European Machine Vision Association) released a preliminary version of the first module of such a standard (please see the attached PDF).



Hi,

Where is the attached PDF ?