Home made "Lens Test Target"

[OzzieTraveller]

G'day all

I'm playing at designing a lens test target and would like some feedback on its layout and suggestions on improvement.

My idea is to create an A4 page that will be copied 5 times and pasted (in a large "X" shape) onto a large piece of cardboard to create a quite large target suitable for most lenses

Below is an 800x600jpg. If anyone wants a copy, I am happy to provide an A4 x 1200DPI PDF for your own use

Regards, Phil
http://i48.tinypic.com/1177d6f.jpg

[I @ M]

Interesting project Phil. :th3:

I would like to make a few quick suggestions ---

Include differing crop factors in your aps-c scale to cater for differing brands eg. Canon 1.3x and 1.6x so that the 25x reference can be quickly and easily read for all makes.

Stress the importance of the fact that an absolutely flat plane relationship both horizontally and vertically between the target and sensor (film) is necessary in order to obtain scientifically valid results. I am not an expert ( let alone basically skilled in lens testing ) but I understand this area to be the hardest bit to achieve without a very controlled environment and it is the part that will show discrepancies in results the quickest by introducing false decentering and field curvature indications.

[kiwi]

Nice

how do you judge backfocus or frontfocus for camera fine tuning ?

[jev]

You might need to have something that will tell the resolution of the lens (linepairs / cm). I'ld suggest to add converging lines that are marked horizontally on the number of lines per cm.

Isn't there some kind of ISO spec chart somewhere?

[I @ M]

Nice

how do you judge backfocus or frontfocus for camera fine tuning ?

Darren, I don't think focus testing was ever an aim of this style of target, it is more to compare resolution, sharpness and chromatic aberration qualities of varying lenses.
Focus test charts are a very much different fettle of kish entirely.

[kiwi]

yes, but I wonder if you simply had a scale whether you can have a one for all chart

[I @ M]

yes, but I wonder if you simply had a scale whether you can have a one for all chart

Focus testing is usually done correctly with charts or objects with depth and angle to them and that totally destroys the aim of this chart. Two separate areas of investigation requiring two separate approaches Darren.

[kiwi]

OK, one focus chart I have seen is simply a ruler on a piece of paper really

This probably explains why I am not an inventor or designer

[Kym]

Free AF test charts... (They are Pentax but will work with any camera)

http://pentaxdslrs.blogspot.com/2008/06/part-1-autofocus-adjustment-for-pentax.html

[OzzieTraveller]

Thank you Andrew for your first posting/suggestions

I had made the presumption that people on this forum would be wise enough to mount camera & tripod at right-angles to the wall upon which the targets were stuck ... perhaps you're right tho ;-)
Otherwise, space & font size on the A4 original becomes an issue with more columns of numbers for different crop sizes, 4/3rds etc etc

The main idea that I'm playing with is to create "something" that I can use with various lenses in order to obtain a feel for lens sharpness etc etc ~ and to arrange for a meet of the Canberra mob so that we can have some fun doing comparisons

As I understand it (from my RMIT days way back in the 60s), the ISO & lines/mm resolutions require hi-res film that is then viewed via a microscope to obtain an empirical result. None of this is available to me, and I don't want to go this far down the track ... I just want to get some idea of lens performance against price against manufacturer etc etc

Regards, Phil