Subscriber Discussion

Field Reference Charts For Testing Resolution

OK, I know of the Snelling Eye Chart used for checking our own eye performance, but what other reference charts are availble for use in the field to assist with comparing video camera performance in the field? I cant seem to remember the name of the one used in the UK that starts with and "R" (I think).

What other devices / charts can be used and what are their dimensions so I can reproduce them on an enlarged CAD plotter?

Thanks all.

I think an eye chart, a license plate and a human subject is fine for real world field use. They will tell you very reliably how good or bad cameras are for that scene.

The UK offering is the Rotakin. I've never understood it and wish someone could explain the advantages of it (beyond that the UK seemingly requires it - which is irrelevant in the US). Years ago, I inquired about it and it cost ~$1,000 for the board itself and another $300-$500 for the manual to use it.

I agree with John's answer. For fine-grained lab testing, a proper resolution chart, and lighting, is essential to get readings that are based on (mostly) repeatable testing criteria. Those kinds of test will give you what amount to best-case scenarios under tightly controlled conditions.

In a real-world case you don't really care about the maximum number of tiny black and white lines you can see in some part of the FOV. You want to read a plate or recognize a face or whatever at some distance. The mug shot + eye chart + license plates + dollar bill test board is pretty universal and gives you the ability to check for the most commonly requested "I want to see X at Y" requirements and perform basic demonstrations.

The rotakin is useful for end-to-end testing of a CCTV system. One of the things people don't understand is why the original version developed by PSDB in the UK rotated (hence the name rotakin). This is very useful for revealing dynamic image problems that can occur during MPEG encoding. For example an anti-alias filter can halve the vertical resolution of the image - but because it only happens on moving objects, you don't notice it unless the test chart is moving. I agree a cost of a $1,000 is crazy for a piece of painted wood - but you can make a reasonable facsimile by printing out some test charts and pasting them to a piece of board 1.8 meters high. There are plenty of images, videos and other information about Rotakin on the internet.

Thanks everyone for the useful feedback. I like the KISS principle to the responses. Just using simple objects makes sense to me.

thanks again

For whatever it is worth, I am giving below a link that gives detailed instructions on how to make your own test targets. This is a UK government recommended procedure. The tests are designed for human identification, vehicle registration number legibility, colour rendition and resolution. The material is free for download. Be warned that the file is about 250 MB. Disclaimer: I have not personally tried making the test targets. and the file is

Jayant, thanks for sharing. Unfortunately, I cannot find the link/download. Can you share the full URL?

Btw, when looking for that, I found the 'Norman' which looks like the Rotakin and costs almost as much.

@jayant and others : the full link is:

[Withdrawn] Imagery Library for Intelligent Detection Systems - GOV.UK

CCTV Test Targets zip download

look in section "Testing CCTV image quality"

Martin Gumm

Independent IP video consultant