Multiple 67mm ND filters on 18mm-135mm lens
 

I need to shoot in bright sunlight this weekend and i was wondering if buying 4x .6 ND filters would cause vignetting. I'm pretty sure it does but want to be sure, just got the 7d and i don't have time to wait for a Vari ND.

If multiple filters are no good, would 1x .9 be enough?

Is there any local stores in the Los Angeles area where i could find a Vari ND?

Beware - stacking ND filters the same size as the lens could lead to vignetting - better go oversize using stepdown rings.

Agree with Jay..... several filters will cause vignetting at wide angles. Your other option (in a pinch) is just zoom in until you clear the vignette. It'll cost you wide angle shots, but if you can't find step down rings or a varizoom, it'll work.

If you're outdoors in bright sun you'll need a .9 to work in the mid ranges of your lens. As mentioned above, best to get larger sizes and a stepdown ring. You might think about what your next lens would be--for example, a 72 or 77mm, and get ND filters in that size with the stepdown ring. However, you can probably get by with 2 filters on that lens and no vignetting, but be prepared to lose a couple of millimeters at the wide end if it happens. Still, I'd go for larger filters that you could use with nearly any lens you might get in the future.

Also, you'd probably want a .9 for most shots and a .3 or .6 to stack on if you're interested in shallow DOF for closer shots. The .9 will get you down to around 5.6-8 in the bright sun.

Thanks Bill, i got new lenses.

Canon 35mm 2.0
Tokina 11-16mm 2.8

...and i have the stock Canon 18-135mm f/3.5-5.6

They all have different thread sizes so i got 0.6NDs for each one and step-up rings to 82mm since i have a Polarizer 82mm and Haze-1 82mm. With the Tokina at 11mm i get a big vignette but i goes away around 14mm with the 82mm filters on it.

I will be shooting a house in full sunlight so based on what you are saying, i should probably return the .6's and get all .9s right?

Thanks for the help.

Stacking ND filters on the wide end of a lens on a full frame sensor camera would be asking for vignetting, but on the 7D with the 1.6x crop factor APS-C size sensor you should be OK.

I stack .6 and .9 filters on the 18-55 IS "kit" lens that often comes with the Digital Rebels and zoomed out to the wide end (18mm but 28mm equiv on FF) I get no vignetting. Same setup on the 24mm F2.8 (about 38.8mm FF equiv) again no vignetting and on the 50mm F1.8, same story.

The 2 filters together give about 5 stop reduction in light transmission and while the eye level finder gets super dark, the LCD live view and video compensate nicely.

I am certain this is too late for you Martin but here is a product that we offer:

67MM ND 1.8-64X (106) - Schneider Optics

Vari-NDs are simply two polarizers that are crossed to reduce light. They most commonly have issues of blue leak where the image turns blue and can't be accurately white balanced. Standard NDs are a much better bet for quality of image.

Ryan Avery
Schneider Optics