How Do I Test My Lenses?

Hi all,

I have a number of ENG zoom lenses that I use on HD and SD cameras. I can subjectively describe the strengths and weaknesses of these lenses. But I would like to know how I can objectively measure(resolution, contrast, tracking, linearity, chromatic aberration...?) them...myself. Or is this testing that requires specialized gear/knowledge?

I appreciate your assistance.

David Brown
St. Petersburg, FL
DP for documentary and news production

David Brown wrote:

>> I would like to know how I can objectively measure(resolution, contrast, tracking, linearity, >>chromatic aberration...?)

Hi David,

Have you looked at Imatest?

http://www.imatest.com/products/software/studio/compare

Jeremy Pronk
animal logic

>>how do I test my glass?

Resolution is fairly simple with a resolution chart. There are also charts for pretty much any of the other attributes, but I'd argue that it's equally important to just put a picture up and subjectively look at it.

That said, get yourself a set of charts and a good monitor and you can test up to the limits of your camera and monitoring system. That way if the lens is holding you back you'll know. But nothing substitutes for looking at actual pictures under various conditions.

I know it's vague, but that's what I do.

Ryan Bedell
DP
Williamsburg, VA

David Brown wrote:

>>Hi all,

>> I have a number of ENG zoom lenses that I use on HD and SD cameras.

If I may be so bold. You can check out:

http://www.gladstonefilms.com/media/Lenstestarticlewithphotos.pdf

Technical testing is important, but don't forget to test the lenses on a face.

--
Steven Gladstone
New York Based Cinematographer
Gladstone films
http://www.gladstonefilms.com
917-886-5858

You'll want a resolution chart, a greyscale, some black theatrical felt or similar and a very small, sharp point source which can be something shiny and reflective or a bare mini-maglite bulb against a black background. Also a good idea to include a colour chart. If you can include a large black (theatrical felt) area adjacent to a bright white area (preferably a piece of backlit diffusion - it should be overexposed) that will be useful too.

These things will give you an idea of contrast, flare and resolution (and colour) and hopefully show the areas where they overlap as well. Shoot at different stops at proper exposure as well as over and under. Shoot in focus and out of focus to get a feel for bokeh.

This type of set up is also great for filter testing.

When using a human subject for testing, try to include some shiny jewellery.

Good luck!

Anders Uhl
dir/dp
east coast, us

Something I've always done to test my lenses is paste up the classified section of the newspaper on the wall, and then shoot it with the lenses I'm interested in. Make sure you're perfectly square
to the wall.

The fine text of the newspaper is great for seeing sharpness and chromatic aberrations.

I guess this is still a subjective test, as you won't get quantifiable results, but you will have an apples-to-apples comparison of all the lenses you test.

Charles Taylor
DP
Toronto, ON

>>Something I've always done to test my lenses is paste up the classified section of the newspaper >>on the wall, and then shoot it with the lenses I'm interested in.

Better move quickly, while (a) your newspaper still has classifieds, and (b) you still have a newspaper.

Printing out pages of craigslist ads just doesn't seem to work as well...

sigh,

Adam Wilt
filmmaker, Meets The Eye LLC, San Carlos CA
tech writer, provideocoalition.com, Mountain View CA
USA

Adam Wilt writes:

>>Better move quickly, while (a) your newspaper still has classifieds, and (b) you still have a >>newspaper.

You can always use printed copies of the US Constitution, while we
still have one.

>Dan Drasin
Producer/DP
Marin County, CA