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09-10-2012, 10:31 AM   #1
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Please explain AA filter and consequences of having/not having it.

While reading threads/posts on the "upcoming" and "rumoured" cameras, I often come across serious discussions about the need to keep or get rid of the AA filter for sharpness issues.
Then there is the "Moiré" pattern ... although not a scientist, I least I know what that in physics, a moiré pattern is an interference pattern, but that is the end of my knowledge as it applies to photography (the absence of an AA filter).

Can someone here offer a not-too-scientific explanation as to the "consequences" of not having an AA filter, in a way I can understand?

Under which type(s) of photography would one want no AA filter, for instance?
What sort of images would be positively/negatively impacted by the no-AA filter business?
Does the quality of the lens used make any difference IF the camera has no AA filter?

Cheers.

JP

09-10-2012, 10:45 AM   #2
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Here is an explanation and sample.

Understanding Digital Camera Sensors
Images with small-scale detail near the resolution limit of the digital sensor can sometimes trick the demosaicing algorithm—producing an unrealistic looking result. The most common artifact is moiré (pronounced "more-ay"), which may appear as repeating patterns, color artifacts or pixels arranges in an unrealistic maze-like pattern


Basically there isn't enough information for the smaller details to resolve, the information is only captured with for example blue and green pixel but not the red so you're missing colour information which can lead faulty "pixel" with moire you've a pattern that goes across the image, brick wall for example so the error occurs repeatedly creating a false incorrect pattern of wrong pixels.
That why AA filter is used to blur the image slightly so that the smaller details is spread out over more pixels.

Negative impact of such filter is that the image is ever so slightly blurred but you don't get strange patterns or wrong colours.


If i understand it correctly the need for AA filter gets smaller the higher the pixel count but i can be wrong.
09-10-2012, 10:49 AM   #3
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QuoteOriginally posted by Anvh Quote
If i understand it correctly the need for AA filter gets smaller the higher the pixel count but i can be wrong.
That is correct.

Nikon D800 D-SLR Camera | High Dynamic Range Camera

Scroll down to the bottom - there's a guide as to whether you want an AA filter or not.
09-10-2012, 10:58 AM   #4
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Moire patterning occurs when the image contains fine lines (such as in fabrics) that are spaced by about one pixel from each other in the image, causing false color due to the lines being resolved as different colors through the Bayer color filter array used on almost all image sensors (a notable exception being Foveon). The low-pass filter suppresses moire patterning by applying a subtle directional blur to the image. This slightly reduces image sharpness, but reduces the incidence of distracting moire and false color. Removing the low-pass filter (or reversing its effects, as in the Nikon D800E) increases sharpness so that the maximum resolution can be achieved. However, if you're shooting fabrics or other subjects that can trigger moire patterning, you'll need to remove the moire in post-processing. Most digital cameras have low-pass filters; however, medium-format digital cameras generally do not have low-pass filters to ensure that the highest level of detail is captured. Nikon explains this in further detail here.

--DragonLord


Last edited by bwDraco; 09-10-2012 at 12:22 PM.
09-10-2012, 11:13 AM   #5
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Still fuzzy to me...............my question, is this an upgrade to my K5?

If I'm not shooting fabric patterns, do I care?

Is that the major change to the new K5? what about AF?
09-10-2012, 11:39 AM   #6
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QuoteOriginally posted by GDRoth Quote
If I'm not shooting fabric patterns, do I care?
Be careful about this, because this can come into play if you're taking pictures of people because their clothing can sometimes cause moire patterning.

QuoteOriginally posted by GDRoth Quote
Is that the major change to the new K5? what about AF?
The rumors state that the new AF system in the K-5 II will be more sensitive for better low-light performance, and that there will be an f/2.8 high-precision point.

--DragonLord
09-10-2012, 11:47 AM   #7
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QuoteOriginally posted by GDRoth Quote
Still fuzzy to me...............my question, is this an upgrade to my K5?
If it were me, on a 16 MP camera, I'd be a bit hesistant. I'd probably still want to remove it. I'm not into fashion photography, though.

On a 24 MP camera I'd definitely want to remove it.
09-10-2012, 11:53 AM   #8
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Basically, without the filter its sharper, but can have some other problems in certain situations. From what I've heard, not all K-5II will be without filter, there will be a separate version, the K-5IIs that will be without filter. So it will be up to you to decide.
The main difference between the old and new K-5 will be the AF system, but possibly other things (we should wait for official specs and maybe reviews). Will it warrant an upgrade from a K-5? Not necessarily, depends on your usage, your experience with the current camera, and your budget

09-10-2012, 12:13 PM   #9
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I guess we should't write the reviews until after 6PM EST..............
09-10-2012, 12:26 PM   #10
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QuoteOriginally posted by GDRoth Quote
I guess we should't write the reviews until after 6PM EST..............
Off-topic: Not to nitpick, but we are currently in Daylight Saving Time, so this should be 6PM EDT. We should see the announcements in about 2 1/2 hours.

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09-10-2012, 12:42 PM   #11
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QuoteOriginally posted by GDRoth Quote
If I'm not shooting fabric patterns, do I care?
I think 99% of us Pentax DSLR shooters does some Post Processing. Removing some local moire pattern in PP takes about 2 seconds. So I never really understood why not all prosumer grade DSLRS are without low pass filter.

Hopefully, there will be an option to remove the low pass filter for existing K5 bodies. I don't care about upgraded AF, my K5 focusses just fine, even in low light.
09-10-2012, 01:40 PM   #12
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QuoteOriginally posted by ElJamoquio Quote
If it were me, on a 16 MP camera, I'd be a bit hesistant. I'd probably still want to remove it. I'm not into fashion photography, though

A fair portion of my work is "dealing somewhat" in fashion photography - and working directly with some of the leaders in that field; in places like NYC, Paris, Milan, etc... I'm presently negotiating a deal with Buckle - and also already do contract work with eleven other clothing type lines.

I would even be willing to risk being an early adopter of the newer version of the K-5 -and then even use it in items like the above mentioned fashion pics; and even as a type of back-up camera for weddings, main line camera for senior portraits, even portfolios.

I've had very little need to actually "edit out" the effects of not having the AA. Although also noting it is not a complicated procedure under CSxx (whatever the version is - either or without plug-ins). But I also do not remember off hand IF the feature to edit such is actually included (or bundled) with items like the included SilkyPics (even as an option) or also if it's available on items like less costly versions of CSxx.

To conclude with my perspective... Yes I'll be upgrading - mostly because my budget would allow it. But I'll also be keeping the current K-5 as well. The only literal consideration is IF someone does have the post-processing that allows the AA to be adapted for. Btw, I also know a number of pro's who rarely even touch digital post-processing; even so far as having someone do it for them if that need ever comes about
09-10-2012, 03:48 PM   #13
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QuoteOriginally posted by ElJamoquio Quote
That is correct.

Nikon D800 D-SLR Camera | High Dynamic Range Camera

Scroll down to the bottom - there's a guide as to whether you want an AA filter or not.
It's funny how they really try to convince the buyer to not get a D800E.
09-10-2012, 04:45 PM   #14
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QuoteOriginally posted by Anvh Quote
Here is an explanation and sample.

Understanding Digital Camera Sensors
Images with small-scale detail near the resolution limit of the digital sensor can sometimes trick the demosaicing algorithm—producing an unrealistic looking result. The most common artifact is moiré (pronounced "more-ay"), which may appear as repeating patterns, color artifacts or pixels arranges in an unrealistic maze-like pattern


Basically there isn't enough information for the smaller details to resolve, the information is only captured with for example blue and green pixel but not the red so you're missing colour information which can lead faulty "pixel" with moire you've a pattern that goes across the image, brick wall for example so the error occurs repeatedly creating a false incorrect pattern of wrong pixels.
That why AA filter is used to blur the image slightly so that the smaller details is spread out over more pixels.

Negative impact of such filter is that the image is ever so slightly blurred but you don't get strange patterns or wrong colours.


If i understand it correctly the need for AA filter gets smaller the higher the pixel count but i can be wrong.
QuoteOriginally posted by ElJamoquio Quote
That is correct.

Nikon D800 D-SLR Camera | High Dynamic Range Camera

Scroll down to the bottom - there's a guide as to whether you want an AA filter or not.
Thanks for the info, guys!

And while we are on the subject, what effect would that have if I were to, (eventualy?) buy into the "new" K5, either the K5 II or the K5 IIs ... one has the AA filter while the other doesn't.
I am into wildlife photography, using telephoto lenses most of the time, and details are a must. So is "resolution".

So, after taking a look at the Nikon write up, with very examples, about Moiré patterns, I suppose I am better stick with a camera which still has the AA filter. Right?

Of course, I do, once in a while, dig into "portrait" stuff (for family stuff only): would the AA filter-less camera cause any sort of Moiré patterns in a "face shot" ? Perhaps on the person's clothing, but what about hair and facial details?

JP
09-10-2012, 04:46 PM   #15
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I guess hair could theoretically cause a problem but I've never seen or heard about it. The facial details would be AOK.
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