About a year ago I wrote a review of the Fotga 77mm ND filter. Though this filter certainly wasn’t brilliant the ultra-low budget price certainly in my mind made up for its shortcomings, making it a product that I recommend for those shooters who don’t use a ND filter all that often and may not necessarily need the highest quality image.
Since writing the review I’ve had a number of inquiries as to the sharpness of the filter. This was something I had knowingly overlooked in my first review, as I hadn’t really had any problems with the filter in this regard. It turns out however that others had found the filter became softer as longer lenses were used. I’ve decide to run my own review of Fotga 77mm ND filter to determine if this in fact is true and if it is, at what focal does image quality begin to degrade and become unusable. The other tests I saw also only tested the filter at f2.8. Moreover, as I often use my ND filter to go for long exposure times I’ll be testing the filter at various apertures and focal lengths to find out just how well the Fotga 77mm ND filter sharpness really is.
To ensure the most accurate results all test images were taken on a tripod using a cable release.
The camera (a Canon 550D) was set to manual mode. ISO was set to 100, while shutter speed was used to set the exposure using the in camera light meter. The light used was standard white florescent lighting (the ambient light in the room).
I used three different lenses for the test: a Canon EF-S 10-22, a Sigma 50mm DG EX 1.4 and a Sigma 70-200 DG EX HSM II.
To test the filter out for different shooting scenarios. I took test images at f2.8, f5.6, f11 and f22 for all the lenses with the exception Canon, which cannot be set below f3.5. I also decide to text the focal lengths 10mm, 22mm, 50mm, 70mm and 200mm. As each lens perform differently, I shot all these focal lengths and apertures with and without the filter to have a point of comparison. The filter was set to ‘Min’, as indicated on the side of the filter (see below), though in actuality it was slightly dark than minimum. At this setting the filter provide a drop in light of nearly 2 stops of light.
Finally, as ND filters have reputation for making focusing difficult, I decided to focus all shoots in live view zoomed in at 10x to ensure the sharpest image possible.
After reviewing the images in depth, I am of the opinion that the filter made no difference to the sharpness of the lens when the aperture was only thing changed. Meaning that that if I shoot an image at f2.8 or f22 using the same the focal length that the filter behaved the same way. For this reason I’ve only included the different aperture test images for the first set of images.
The Canon EF-S 10-22 at 10mm
As you can see the aperture appears to have no impact. At 10mm I also struggled to find an degradation in the sharpness. The color shift I noticed in my first review is definitely still visible.
The Canon EF-S 10-22 at 22mm
20mm is a similar story as 10mm. The image looks equally sharp with and without the ND filter and the color shift is equally as strong.
The Sigma 50mm
Given some of the results I’ve read online, I was expecting the filter at 50mm to show some significant softening. And though I would say that the image with the ND filter is softer, the difference is minute. In fact, I had to zoom in 2:1 to really make the decision. Slightly softer but certainly usable.
Sigma 70-200 at 70mm
Things are beginning to get a little soft. Well, maybe that’s being kind. For me this is just too soft.
Sigma 70-200 at 200mm
The softest test yet, and for me an unusable result.
If you’re looking for the ultimate in performance this definitely is not your filter. In fact, if you’ve got a bit of money to splash out and are looking for a versatile filter, I probably wouldn’t recommend this filter for you either. But I do believe this filter has a niche. If you’re a new photographer curious about ND filters, an occasional user of an ND filter or think you’ll typically use an ND filter for ultra-wide shots I don’t think you can wrong with the Fotga with it’s 15 dollar price tag. If you’re planning to use this filter with a telephoto you’d be better off saving your money.
Let’s take one final look at the Fotga 77mm ND filter’s pros and cons.
- Super Cheap
- Fair build quality
- Works well with wide-angle lenses (up to at least 22mm)
- Is acceptable with mid-range telephotos (should work ok on a 24-70)
- Produces a color shift (although this is common in many more expensive ND filters and can be corrected in post)
- Produces significant dark patches at darker settings
- Extremely soft when zoomed to 70mm or beyond*
* I would like to know at which point beyond 50mm and 70mm that the image quality really becomes unusable. I am planning to buy a 24-70 in the next few months and will update this page when I have a chance to test this.