Background: I misplaced my filter wallet at an outing two years ago, in it were the filters I used on a regular basis, among them, the gradual ND filters. So I had to purchase some new filters.

I know some may argue that this is the digital era and with the post processing in Photoshop and/or other software, filters are no longer needed. I am well aware of the capabilities of the editing software but it's just my personal preference - when given the choice, I'd rather spend the time taking pictures in the field than sit in front of the computer for the same effects.

Anyway I decided to go with the Cokin filters, because I've always used the Cokin system (holders but not their ND filters) and they are inexpensive. The only legitimate complaints I've heard are that they have a magenta color cast, and that they get scratched easily (but so do other higher priced resin filters). I thought I would give them a try, and if the color cast was really that bad I would just replace them, or use Photoshop to get rid of the color shift if they are relatively minor.

Fast forward - it has been almost two years since I got the Cokin gradual ND filters (0.3, 0.6 and 0.9), somehow I just don't see the infamous color cast I've heard so much about in my images. So I decided to run a quick test so see if I have missed something. Here's what I did:

I set up a towel in the mid-morning sun (around 8:30) and took pics. of it at 0EV, -1EV, -2EV and -3EV using exposure compensation. I then set the camera back to 0EV and manual exposure mode, and took pics. with the Cokin 121L, 121M, and 121 (corresponding to the reduction of light of 1 stop, 2 stops and 3 stops respectively, and these are soft-edge filters). The images are JPEG straight from the camera with no PP except cropping; white balance was set to AUTO.

No filter at -1EV:
http://cmsfoto.zenfolio.com/img/v5/p983612063-4.jpg

With Cokin 121L (one stop):
http://cmsfoto.zenfolio.com/img/v6/p917585729-4.jpg

No filter at -0.7EV
http://cmsfoto.zenfolio.com/img/v0/p763887964-4.jpg

Comparing the images with and without filters, I don't seem to detect any color shift (there is, however, a 0.3EV difference between the -1EV and 121L images, but the -0.7EV image looks identical to the image with filter). So my questions are:

1) Did I miss anything?
2) As stated previously, these filters were purchased less than two years ago. Is it possible the color cast problem has been fixed on the new Cokin filters? Or the color shift only exists on Cokin's glass ND filters? Unfortunately I don't have any Cokin glass ND filters so I can't verify the latter.

Note: I am only showing the comparison of -1EV (w/o filter) and that from Cokin121L because the colors are most vivid with one stop reduction and easy to compare; but the results from 121L, 121M and 121 are practically identical in terms of color shift.