Zomei Slim Graduated Grey Neutral Density Nd Filter Review
I recently purchased a video-capable DSLR (Digital SLR) camera and wanted some ND filters (neutral density filters). I purchased some Zomei resin ND filters from ebay. Zomei is Chinese, but they make lots of filters and the products are nicely presented. There was very little feedback about Zomei on the web and then I wrote this review.
I found that the Zomei resin ND2 and ND4 filters were satisfactory. For the ND8 filter, exposure was inaccurate and colour errors were relatively large.
Update: The cases of the Zomei filters I tested are labelled 'ROHS HD RESIN' and 'PRO OPTICAL FILTER Black almite frame' on the front. The backs of the cases point that the filters are manufactured in partnership with Bingo Network Technology Co. Ltd. Some readers accept commented below that Zomei have some glass filters that are satisfactory. In writing this post, I did not intend to trash all Zomei filters.
Filters tested
I tested Zomei ND2, ND4 and ND8 58 mm filters. The filters are well made and the threads are good. The filters are not multicoated.
Zomei ND2, ND4 and ND8 filters.
I immediately noticed that the Zomei filters felt different, because they are made from high-density resin. Some Zomei filters use glass, but these ND filters were plastic! The ebay seller had incorrectly stated they were import optical glass (and promptly removed the listings after my negative feedback).
I also tested Kenko SMART ND8 52 mm and ND8 77 mm filters to compare with the Zomei results. The Kenko filters have a slim frame and are not multicoated. They were made in the Philippines, I think using drinking glass from Japan.
Methods
I photographed an X-Rite ColorChecker Passport in sunlight on a clear afternoon (uniform and stable lighting is required) with a Canon EOS 350D DSLR and EF 85 mm f/1.8 lens. I fix the base of operations exposure (one/500 seconds shutter speed) with a xviii% grayness carte du jour and photographed the ColorChecker four times with fixed aperture f/eight and fixed ISO100:
- No filter and base exposure before.
- ND filter and base of operations exposure.
- ND filter and exposure compensation (slower shutter speed: +i terminate for ND2, +2 stops for ND4 and +3 stops for ND8).
- No filter and base exposure after.
The residual of this section is very technical and for specific software. Y'all might adopt to jump over to the results.
Linear device RGB is required. I candy each image in Raw Therapee version four.1 as follows:
- Processing Profile = Neutral (disables nearly adjustments).
- Input Contour = No profile (device RGB).
- Output Gamma = linear_g1.0 (linear RGB).
- Custom white balance on the third-lightest grey patch of the ColorChecker (any neutral low-cal-greyness patch should piece of work).
- For image ii, apply linear exposure White Point Correction (2× for ND2, 4× for ND4, 8× for ND8).
- Crop to ColorChecker target.
- Save as TIFF (16 bit).
Rather than applying exposure compensation to epitome two, I could have but used epitome 3. The shutter speeds should exist authentic enough.
I used Argyll CMS to read the ColorChecker patches from each linear RGB TIFF image:
scanin -v -p -a -G1 -dipn input.tif ColorChecker.cht ColorChecker.cie
-five verbose.
-p compensate for perspective distortion.
-a nautical chart orientation normal (non upside down).
-dipn generate diagnostic image.
-G1 Gamma encoding of paradigm (linear).
input.tif is the input image and input.ti3 is the name of the output text file.
ColorChecker.cht is a nautical chart recognition file.
ColorChecker.cie contains the the nautical chart reference data (which is copied to the .ti3 output file).
I copied the scanin output to a spreadsheet. I compared white patch average RGB values with- and without filters (they should all be the aforementioned if lighting and exposure were the same).
Adjacent, I used Argyll CMS to compute colour differences relative to the ColorChecker reference data. For this, I had to match the exposure of images 1 and 3 to minimise lightness differences increasing the colour differences. I used image 3 because it has a better signal to noise ratio than the underexposed image 2.
I had previously made my own camera contour for the Canon EOS 350D and matched white patch average RGB values to that profiling prototype. Alternatively, one could just profile image 1 as the reference. After applying linear exposure White Point Corrections in Raw Therapee, I ran scanin again and then profcheck to evaluate colour differences:
profcheck -v2 -k prototype.ti3 profile.icc
-v verbosiy level 2.
-k report CIE Delta-East 2000 colour differences.
input.ti3 is the output from scanin.
profile.icc is the camera profile.
Argyll CMS profcheck takes the patch RGB values from the .ti3 file, applies the camera profile and computes color differences with the chart reference data in the .ti3 file. I repeat: to minimise lightness errors, the exposure of the image must friction match the exposure of camera profiling image.
I copied the profcheck output to a spreadsheet. I compared average DE2000 differences with- and without- filters.
Exposure errors
Afterward three-stops exposure compensation, the Zomei ND8 filter was even so underexposed −0.49 stop relative to the images without any filters. The ND4 filter was improve (−0.17 stop) and the ND2 was skillful (+0.02 cease). The ND8 filter was finer a ND11 filter (2^(three+0.49) = 2^3.49 = 11.two), i.e. the effect is stronger than 8×.
Zomei ND filters exposure errors. Exposure compensation was applied to the ND images (+1 stop for ND2, +2 stops for ND4, +3 stops for ND8) before making these comparisons. Numbers above the columns are exposure errors in stops = log(RGB/RGB_before) / log(2). The before and after measurements without whatsoever filters agree, which indicates that the lighting was abiding during the tests.
For comparison, exposure errors for two Kenko ND8 filters were much smaller at −0.xiv and −0.12 stops.
Colour errors
The 3.3 boilerplate colour error for the Zomei ND8 filter exceeded a just noticeable difference (DE > 2) and the maximum was 6.4. Colour accurateness was satisfactory for the Zomei ND4 filter (average DE = 2.0) and good for the ND2 filter (boilerplate DE = 1.6).
Zomei ND filters color errors. Numbers above the columns are average DE2000 colour errors (DE = ii is a only noticeable difference). The earlier and after measurements agreed closely and average colour differences were small (DE < two). This indicates: ane) the lighting (afternoon sun) was similar to lighting for the camera profile (morn sunlight) and, 2) the lighting was abiding during the tests.
For comparison, average colour errors for two Kenko ND8 filters were much smaller at 1.5 and 1.4 stops.
The following two charts highlight the colour differences when using the Zomei ND8 filter.
Colour differences for 24 ColorChecker patches. No filter. Nearly differences are pocket-size (DE < 2) and were like to the camera profiling errors.
Colour differences for 24 ColorChecker patches. Zomei ND8 filter. Many differences exceed a but noticeable difference (DE > ii).
Conclusion
We can utilize a ColorChecker chart, Raw Therapee and Argyll CMS to evalute ND filters.
The Zomei ND filters were increasingly inaccurate for college densities. Results for the Zomei ND8 filter were unsatisfactory. This doesn't mean that filter is useless, however it is not the 8× (3 terminate) and neutral density (DE < ii) filter that we want. Results for Kenko filters showed that authentic ND8 filters are doable.
Disregarding the ND8, I purchased 2 Zomei ND filters for AUD22 (AUD11 each). The Kenko filter was AUD19 (for 58 mm diameter). I retrieve it is worth paying more than for better quality drinking glass ND filters.
Source: https://stephenstuff.wordpress.com/2015/03/19/zomei-neutral-density-filters-testing/
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