Fotga 77mm ND Filter Sharpness Test

Fotga 77mm ND Filter Sharpness Test

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.

Methodology

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.

The Sigma 70-200mm DG EX HSM MACRO II, the Canon EF-S 10-22mm, and  the SIgma 50mm 1.4 EX (the lenses used to test the filter)

The Sigma 70-200mm DG EX HSM MACRO II, the Canon EF-S 10-22mm, and the SIgma 50mm 1.4 EX (the lenses used to test the filter)

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.

072_FotgaSharpND-2878

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.

The Results

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

10mm f5.6 with ND

10mm f5.6 with ND

10mm f5.6

10mm f5.6

 

 

 

 

 

 

 

 

10mm f5.6 (100% Crop)

10mm f5.6 with ND (100% crop)

10mm f5.6 with ND (100% crop)

 

 

 

 

 

 

 

 

10mm f11

10mm f11

10mm f11 with ND

10mm f11 with ND

 

 

 

 

 

 

 

 

10mm f11 (100% crop)

10mm f11 (100% crop)

10mm f11 with ND (100% Crop)

10mm f11 with ND (100% Crop)

 

 

 

 

 

 

 

 

 

 

 

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

22mm f5.6 with ND

22mm f5.6 with ND

22mm f5.6

22mm f5.6

 

 

 

 

 

 

 

 

 

22mm f5.6 (100% crop)

22mm f5.6 (100% crop)

22mm f5.6 with ND (100% crop)

22mm f5.6 with ND (100% crop)

 

 

 

 

 

 

 

 

 

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

50mm f5.6

50mm f5.6

50mm f5.6 with ND

50mm f5.6 with ND

 

 

 

 

 

 

 

 

 

50mm f5.6 (100% crop)

50mm f5.6 (100% crop)

50mm f5.6 with ND (100% crop)

50mm f5.6 with ND (100% crop)

 

 

 

 

 

 

 

 

 

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

70mm f5.6

70mm f5.6

70mm f5.6 with ND

70mm f5.6 with ND

 

 

 

 

 

 

 

 

 

70mm f5.6 with ND (100% crop)

70mm f5.6 with ND (100% crop)

70mm f5.6 (100% crop)

70mm f5.6 (100% crop)

 

 

 

 

 

 

 

 

 

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

200mm f5.6

200mm f5.6

200mm f5.6 with ND

200mm f5.6 with ND

 

 

 

 

 

 

 

 

 

200mm f5.6 (100% crop)

200mm f5.6 (100% crop)

200mm f5.6 with ND (100% crop)

200mm f5.6 with ND (100% crop)

 

 

 

 

 

 

 

 

 

The softest test yet, and for me an unusable result.

Conclusions

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.

PROS

  • 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)

CONS

  • 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.

076_FotgaSharpND-2881

 

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There are 2 comments

  1. Anthony

    Colin,
    Just getting into DSLR and got hold of a second hand canon 50D off a friend. Also came with this fotga variable ND filter. How do I find out which ND the markings are. Apart from min and max there 9. The filter is from ND2 to ND400.
    Looking at tables the ND setting don’t add up.
    Cheers.

    • Colin Jones

      Hi Anthony,

      Different companies use different number systems to show the amount of light an ND filter will block/allow to pass through. An ND1000 for example may also be called an ND 3.0 and both will block around 10 stops of light.

      I think this chart (http://bit.ly/1XvndGx) should help.


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