# Major Problem With the Aurora Aperture ND Filters for the Canon EF 11-24mm f/4L



## Canon Rumors Guy (Jan 20, 2018)

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<a href="http://shuttermuse.com/">Professional photographer Dan Carr</a> recently had a chance to borrow a set of ND filters by Aurora Aperture (<em>edit: the filters were provided by B&H Photo, not Aurora Aperture</em>) designed for the Canon EF 11-24mm f/4L and other Canon ultra-wide angle lenses. These are rear mount filters.</p>
<p>The set of 4 ND filters from Aurora Aperture includes a 3-stop, 6-stop, 12-stop and 16-stop filters. Dan had a level of excitement for the filters, because it seemed like an easy solution to add ND to the EF 11-24mm f/4L. While it doesn’t solve the circular polarizer challenges, it seemed to easily solve the ND issues in a nice and compact package.</p>
<p>However, Dan found softness issues shooting with the 12-stop and 16-stop filters. You cannot use AF or Liveview focus with ND filters this dark. It’s standard practice to focus your shot and then add the filter and shoot. The 3-stop and 6-stop filters will allow enough light through to focus the show with them equipped.</p>


<p><strong>The 12-stop and 16-stop issue as explained by Dan:</strong></p>
<blockquote><p>It was immediately noticeable that the shot was soft. So soft that I didn’t need to zoom in on the image to see it. At first I thought that maybe I had nudged the focus ring during the lens removal procedure, but after 4 or 5 more attempts at the same routine, I couldn’t get a sharp shot. For these tests I was shooting the mountains in my local valley, with the focus being set on extremely distant features, basically at infinity.</p>
<p>I also tested the 16-stop filter and had the same problem, so that ruled out a single faulty filter. <a href="http://shuttermuse.com/major-problem-aurora-aperture-nd-filters-canon-11-24mm/">Read the full story</a></p></blockquote>
<p>If anyone else has used these filters and experienced the same problem, please sound off in the forum.</p>
<p><em><strong>Update:</strong> Aurora Aperture has acknowledged that some photographers are experiencing this issue, and they are investigating the cause. We’ll update if we hear more.</em></p>
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## Mt Spokane Photography (Jan 20, 2018)

I would think that he would get a answer from the manufacturer before publishing the issue. One would think that they may have a answer.

A filter on the very rear of a lens is in a extremely critical place, and flatness is absolutely required. I would be surprised if it worked well. 

Its pretty obvious from his testing that there is a issue, but, if you want companies to loan products to you for trial / review, they should be given a chance.


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## Canon Rumors Guy (Jan 20, 2018)

Mt Spokane Photography said:


> I would think that he would get a answer from the manufacturer before publishing the issue. One would think that they may have a answer.
> 
> A filter on the very rear of a lens is in a extremely critical place, and flatness is absolutely required. I would be surprised if it worked well.
> 
> Its pretty obvious from his testing that there is a issue, but, if you want companies to loan products to you for trial / review, they should be given a chance.



The filters were loaned by B&H Photo, I have updated the story.


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## sbauer (Jan 20, 2018)

I've been using these filters on my 11-24 since they were first available on Kickstarter and have been very pleased with their performance. My process for using these filters is to use autofocus first, without the filter, and then place gaffer's tape on the focus ring of the lens. Then, I turn off the Autofocus, remove the lens to install the ND filter, and then take my exposure. I have not had any issues with out of focus or soft focus images using this method and I've been very impressed with the results. An added benefit is there's no color cast to my images. As a result, I sold my Lee system to include the Big Stopper.


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## Canon Rumors Guy (Jan 20, 2018)

sbauer said:


> I've been using these filters on my 11-24 since they were first available on Kickstarter and have been very pleased with their performance. My process for using these filters is to use autofocus first, without the filter, and then place gaffer's tape on the focus ring of the lens. Then, I turn off the Autofocus, remove the lens to install the ND filter, and then take my exposure. I have not had any issues with out of focus or soft focus images using this method and I've been very impressed with the results. An added benefit is there's no color cast to my images. As a result, I sold my Lee system to include the Big Stopper.



I will say, it doesn't look like the filter in question is fitting into the lens evenly. Do yours fit the same way as the images in the story?


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## sbauer (Jan 20, 2018)

Yes, mine look the same as the photos in the article.


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## Canon Rumors Guy (Jan 20, 2018)

Mt Spokane Photography said:


> I would think that he would get a answer from the manufacturer before publishing the issue. One would think that they may have a answer.
> 
> A filter on the very rear of a lens is in a extremely critical place, and flatness is absolutely required. I would be surprised if it worked well.
> 
> Its pretty obvious from his testing that there is a issue, but, if you want companies to loan products to you for trial / review, they should be given a chance.



I have updated the story. Aurora Aperture has acknowledged the issue occurring for some photographers and are not sure why it is happening, and are investigating the issue.


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## Jack Douglas (Jan 20, 2018)

I wasn't aware of these filters and would appreciate more feedback from users. I was close to buying sheets to cut.

Jack


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## photonius (Jan 21, 2018)

well, wouldn't any piece of planar glass there cause slight shift in focus, effect depending on the thickness? There are enough reports of issues when the same lens is used with different camera bodies (adapting a lens to another brand) that have different thicknesses of filters in front of the sensor.
In this case, probably it also depends on the aperture. Stopped down less of an issue than wide open. Focal length of lens will also have an impact.
In any case, it's assumed the filters are really planar. If not, that's of course another issue.

Edit: I just remember, also with catadioptric mirror lenses that have a filter in the back, if one does not use any of the ND filters, the clear filter should be put in place, so that the optical path is ok, it's supposed to be calculated with that filter in place.


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## Jack Douglas (Jan 21, 2018)

photonius said:


> well, wouldn't any piece of planar glass there cause slight shift in focus, effect depending on the thickness? There are enough reports of issues when the same lens is used with different camera bodies (adapting a lens to another brand) that have different thicknesses of filters in front of the sensor.
> In this case, probably it also depends on the aperture. Stopped down less of an issue than wide open. Focal length of lens will also have an impact.
> In any case, it's assumed the filters are really planar. If not, that's of course another issue.
> 
> Edit: I just remember, also with catadioptric mirror lenses that have a filter in the back, if one does not use any of the ND filters, the clear filter should be put in place, so that the optical path is ok, it's supposed to be calculated with that filter in place.



Yes, the 300 2.8 has a lens in place and it's made me wonder exactly what bearing it would have on the IQ but Canon chose to put it in so it couldn't be that much since its sharpness is undisputed. I bought the polarizing slide in filter but have yet to use it so I can't comment on that effect.

Anyone, where in the path is extra glass the most detrimental and why?

Jack


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## Mt Spokane Photography (Jan 21, 2018)

Jack Douglas said:


> Anyone, where in the path is extra glass the most detrimental and why?
> 
> Jack



Generally, any marks or imperfections on the rear lens element show in photos, but ones on the front generally do not. The closer the issue is to the sensor, the easier it is to mess things up.


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## Mt Spokane Photography (Jan 21, 2018)

Canon Rumors said:


> Mt Spokane Photography said:
> 
> 
> > I would think that he would get a answer from the manufacturer before publishing the issue. One would think that they may have a answer.
> ...



I should clarify. When someone has a issue like this, its easy to say that the world is falling, when its possible that this is a isolated incident. Most lens testers, even those who borrow from B&H, ask for a different sample before pronouncing a product as defective in a general sense.


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## StoicalEtcher (Jan 21, 2018)

sbauer said:


> I've been using these filters on my 11-24 since they were first available on Kickstarter and have been very pleased with their performance. My process for using these filters is to use autofocus first, without the filter, and then place gaffer's tape on the focus ring of the lens. Then, I turn off the Autofocus, remove the lens to install the ND filter, and then take my exposure. I have not had any issues with out of focus or soft focus images using this method and I've been very impressed with the results. An added benefit is there's no color cast to my images. As a result, I sold my Lee system to include the Big Stopper.



sbauer, that sounds like a work around that is giving you the results you want.

However, and this is not intended as criticism, that sounds like quite a workflow to deal with in the field (focus, gaffer into position, remove lens from body, insert filter, re-fit lens...), that I personally would be loath to go to - just thinking of sensor dust for one thing alone. I am genuinely interested in whether you had tried the Lee Sw150 II system for your lens, as to me this is a far preferable method, and if so, what made you prefer the Aurora? (Parking to one side the issue of colour cast with your BigStopper).

I might of course just be a stick in the mud, and so used to using filters the old fashioned way, that any change is "bad" :


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## aceflibble (Jan 21, 2018)

This is why you may as well take advantage of modern technology, not worry about having such a strong ND in the first place, and instead use a lighter ND with multiple exposures and use image averaging to take care of the rest. Bonus is the camera's own focus and metering will work more accurately, less risk of colour shift (and less drastic colour shifts when they do occur), and less noise than even the base ISO would usually give you.

For the few people still shooting to film, okay, I get it, filters like this are vital and it sucks that an otherwise seemingly-decent set has problems at the stronger strengths, which of course is when the filters are most important. But for anyone shooting digital, even if these filters worked perfectly, you're still giving yourself more work and opening your shots up to more photo-ruining risks than is necessary.

Whether it's landscape or product, I can't imagine shooting a digital job with anything more than a 3-stop ND these days, maybe up to a 5-stop if we were talking about really top-quality filters I could be confident wouldn't shift any colours. Beyond that, image averaging becomes so much faster _and_ cleaner. There are some things I rely on physical filters for (polarisation, halation, colour filtering), but ND isn't one of them. At least not to strengths like 16-stops. Save yourself the time, hassle, and risk, and just stack multiple frames. Better, cleaner, more reliable results; less effort; less risk.


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## Hector1970 (Jan 21, 2018)

Maybe you don't do long exposure photography which is quite popular (otherwise Lee wouldn't be selling Little and Big Stoppers). I have a 11-24 and its quite a disadvantage not to be able to easily add filters to it. 
It's an interesting product but I wouldn't invest if it impacts image quality. 
Hopefully it can be sorted out.
Gel filters aren't great. I've tried them in the past.
The Wonderpana solution is huge and makes an already awkward lens even more awkward. It is a very good lens though. It can produce really unusual viewpoints.




aceflibble said:


> Whether it's landscape or product, I can't imagine shooting a digital job with anything more than a 3-stop ND these days, maybe up to a 5-stop if we were talking about really top-quality filters I could be confident wouldn't shift any colours. Beyond that, image averaging becomes so much faster _and_ cleaner. There are some things I rely on physical filters for (polarisation, halation, colour filtering), but ND isn't one of them. At least not to strengths like 16-stops. Save yourself the time, hassle, and risk, and just stack multiple frames. Better, cleaner, more reliable results; less effort; less risk.


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## photonius (Jan 22, 2018)

Jack Douglas said:


> photonius said:
> 
> 
> > well, wouldn't any piece of planar glass there cause slight shift in focus, effect depending on the thickness? There are enough reports of issues when the same lens is used with different camera bodies (adapting a lens to another brand) that have different thicknesses of filters in front of the sensor.
> ...



comments "stolen" from another board:

---
- If the lens accepts a filter at the rear, you must always use a filter, clear or otherwise. You must use one which meets the design specifications by the lens manufacturer.

A filter increases the optical path length by a distance of about 1/3rd the thickness of the filter. This effect is negligible if the filter is in front of the lens since the lens to subject distance is relatively large, and the lens can always be focused in compensation. Behind the lens, the effect is usually significant, again because the distance is small. Since it increases the effective distance, it may not be possible to focus at infinity.

- It is one of those "photographic myths" that a filter must always be either in the "drop-in" position, or the rear for those lenses equipped with same. The filter will shift the focus to the degree of t(n-1) where t is the thickness of the filter and n is the refractive index (usually about 1.5). Since glass has the property of dispersion (change of n with wavelength) there will be a slight difference in focus for different colors, but so small that it can be neglected for all practical purposes. Just focus normally, either with or without the filter, and you will never know the difference.

---
In any case, AF focusing or live view focusing will take care of this problem. The problems become apparent with the high ND filters, where AF doesn't work (well). I guess one can always AF with a ND2, fix focus, and then switch.


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## wm700293 (Jan 22, 2018)

Well, the immediately previous remarks regarding the effect of filter thickness would make me want to put a micrometer to the four filters to see if the "12" and "16" filters were significantly "thicker" than the others. One easy way to get more density (darkness) in a filter is to make it thicker rather than changing the relative opacity of the material from which the filter is made. Could this be a contributing factor??? Inquiring minds want to know...


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## sbauer (Jan 22, 2018)

sbauer, that sounds like a work around that is giving you the results you want.

However, and this is not intended as criticism, that sounds like quite a workflow to deal with in the field (focus, gaffer into position, remove lens from body, insert filter, re-fit lens...), that I personally would be loath to go to - just thinking of sensor dust for one thing alone. I am genuinely interested in whether you had tried the Lee Sw150 II system for your lens, as to me this is a far preferable method, and if so, what made you prefer the Aurora? (Parking to one side the issue of colour cast with your BigStopper).

I might of course just be a stick in the mud, and so used to using filters the old fashioned way, that any change is "bad" :

I was using the Lee system, to include the Big Stopper, with my 16-35 and when I got the 11-24 I began to look at an alternative. I understand there might be others with different results but, I've been pleased with the Aurora system. I agree that having to remove the lens to install a ND filter can be a pain and can possibly introduce sensor dust but, I usually just have to do it once and then I'm done. The Gaffer's tape stays on my lens and has not been a problem at all. Additionally, these filters a so much smaller and therefore are in my camera bag whenever the 11-24 is loaded. I'm also interested in hearing from others who have actually used these ND filters. Thanks for the information.


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## Jack Douglas (Jan 22, 2018)

Thanks photonius

Jack


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## jeffa4444 (Jan 22, 2018)

Photonius explaination is indeed correct. If you add filters to the rear you should adjust the back-focus. Personally I would never use rear filters much safer & easier to use at the front (unfortunately not so easy to do with the EF 11-24mm).


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## Steve Balcombe (Jan 22, 2018)

wm700293 said:


> Well, the immediately previous remarks regarding the effect of filter thickness would make me want to put a micrometer to the four filters to see if the "12" and "16" filters were significantly "thicker" than the others. One easy way to get more density (darkness) in a filter is to make it thicker rather than changing the relative opacity of the material from which the filter is made. Could this be a contributing factor??? Inquiring minds want to know...



If you read the article you'll find that the problem also occurs with the 3-stop and 6-stop - if you add them after focusing. It's just that you never actually _need _to pre-focus with those filters, whereas with the very dark filters you have no choice.


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## StoicalEtcher (Jan 22, 2018)

sbauer said:


> sbauer, that sounds like a work around that is giving you the results you want.
> 
> However, and this is not intended as criticism, that sounds like quite a workflow to deal with in the field (focus, gaffer into position, remove lens from body, insert filter, re-fit lens...), that I personally would be loath to go to - just thinking of sensor dust for one thing alone. I am genuinely interested in whether you had tried the Lee Sw150 II system for your lens, as to me this is a far preferable method, and if so, what made you prefer the Aurora? (Parking to one side the issue of colour cast with your BigStopper).
> 
> ...



Thanks for the response, Stoical.


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