Why are there strong AA filters in 4/3rds cameras?

[paul_p3]

Now before someone tells me it's to stop moire, etc. Yes, I know that. But why? Are 4/3rds sensors more

suseptible to it than formats with bigger pixels?

 

I ask because I think I'm not that happy with photos from my E-3 of grass or vegetation. When I moved up from the

5mp E1 to the 10MP E-3, I was expecting a noticable improvment in detail in photos. Now I'm not sure I've got

that. I know a 50% increase in pixels is only a 25% increase in resolution but while my camera/lens will catch

small lightposts on a distant horizon, any grass from 10 - 20m outwards is just rendered like coloured clumps and

there's no definition of single blades of grass or similar in vegetation.

 

I'd shot at ISO200 with the noise filter on low and sharpening at 0. When I tried to USM in photoshop, all it did

was highlight the odd noise speckle amoung the grass detail, this 'detail' being 'streaks' or 'blotches' of

darker hues and shades.. not detail as such.

 

I have a sneaking suspicion that the small pixels means the AA filter needs to be strong to avoid moire, look at

the weaker filtered G1 samples for moire if you don't believe me.

http://farm4.static.flickr.com/3128/2897447593_10d0c47568_o.jpg

 

Now part of my 'issues' are because I'm looking at images at 100%, but I remember doing the same to sigma images

of a Venice townscape including a distant bridge with crowd scene but my chief memory of that image is seeing

spectacles/sunglasses on a head on a tiny person in a big crowd on far bridge, etc. It was truely impressive per

pixel detail.

 

Yet my camera returns clumps of grass sporting 'shades of colour' instead of detail and this is stuff far nearer

to the camera than this sigma stuff I recall. Yet when I zoom out of the E-3 images, they look OK and those

distant 1 pixel wide lamposts have gone near invisible.

 

But lets not make this a foveon V bayer thread: my basic question is do smaller pixels require stronger filters

and thus is 4/3rds heading for a future of more quotes like this:

 

"There is a softness / lack of resolution that robs otherwise perfect shots of the pixel-level crispness that

some of the E-3's competitors can offer. Of course at normal viewing sizes we're not talking about a deal-breaker

here, but if you're likely to really push your E-3 to the limit on a regular basis it could be important."

 

http://www.dpreview.com/reviews/olympuse3/page22.asp

 

I'm not unhappy with the E-3, I'd just expected more from their renowned 'designed for digital', 2x the MTF over

35mm, top-notch lenses on their flagship camera. I always thought that "well, it may be a noisy sensor but it'll

hold its own in recording detail against its peers"

 

Am I expecting too much?

[davidlong]

I don't think there's any particular reason other than the usual (needed to avoid moire). That is, there's no inherent need for a stronger AA filter with a smaller sensor. Different companies make different tradeoffs of moire vs. resolution, and if you want a weak AA filter in a 4/3 camera, an L10 is, at least at present, your best bet.

[patrick j dempsey]

What aperture are you shooting? Maybe you are running into diffraction issues at small apertures? Most lenses are typically sharpest somewhere a few stops faster than the smallest aperture. Most companies offer lenses that go beyond their sharpest settings to give the appearance of a wider range of useful shutter/aperture combinations which originated in film cameras having fairly low top shutter speeds. Now that most digitals offer 1/8000th, having aperture settings beyond the sharpest setting must largely be a marketing ploy, as even the fastest lenses can be shot in bright daylight on low ISO's.

[mike_earussi1]

Just in case you haven't seen this: http://www.maxmax.com/nikon_d200hr.htm

 

This is why Sigma's SD cameras look sharper at the pixel level, no AA filters.

[machts gut]

"I'd shot at ISO200 with the noise filter on low and sharpening at 0."

 

Did you try shooting RAW? Maybe this would make an improvement. Shooting JPG, I would switch off noise reduction and set sharpening to minus. At least this is what many recommend for the 415/510 at ISO 100-400 and why shouldn't the E-3 make it even better.

[paul_miller10]

For the best image quality with any digital camera, set the sharpening to the greatest negative value. In an Olympus DSLR that's -2.

[phule]

[[any grass from 10 - 20m outwards is just rendered like coloured clumps and there's no definition of single blades of grass or similar in vegetation. ]]

 

Can you provide a sample photo that you've taken?

[pedro_esteves]

They have changed to a stronger anti-alias filter for the E3, E420/520 series. You get cleaner images (with less

noise) but with less detail. And because this is at hardware level doesn't improve by shooting raw. Hope they

change it in the next models. Until then I'm not upgrading my E-410.

[laurentbaig]

AA filter has nothing to do with reducing noise - in fact, the filter reduces light, thus would lead to an increase in noise. It only has to do with reducing spatial frequencies (what you are calling moire patterns) and that's it. Noise is controlled by the quality of the photon collectors (CCD or CMOS) and the image processing algorithms on the backend.

 

My guess is it was over-engineered.

[paul_p3]

Patrick, it was above f5.6 and below F10.

 

Stefan, no, I don't shoot RAW as DPreview says there's basically no benefits to it, i.e. there's no more detail

or DR that convertors can get out of the data. I look at that the other way, Olympus have rung every bit of IQ

out of that imaging system as they can without lumbering the user with big file sizes and lengthy raw conversion

routines. ;-)

 

As to the in-camera image settings: I'm just getting used to the E-3, I've had it 10-11mths and I've used it

about 3 times in that period. In fact, I've doubled that usage in the past month alone.

 

Sharpening: I take your point about minus sharpening, used to do that on the E1.

 

Noise Filter: 'Off' or 'Low'? Well it's that compromise you have to make, isn't it? I'd like to use 'Off' but I

think the noise may be too bad as I tend to under-expose to preserve highlights so I'm trialing 'Low' for the

present. I will have to remember to try 'Off' soon.

 

Bob, I tried to provide a sample but, to be frank, I'm not sure what I'm talking about [plus, I can't remember

what compression the jpgs where saved at] so can I retract and give Oly the benefit of the doubt? When I look at

images normally, they are fine so ingore this pixel peeper. I've gone through them again and the shutter speed

dips below the 1x focal length rule and it was quite windy on top of the hill where some shots where taken.

 

One day I'll go out into some fields with grass and trees at near, mid and far distances and shoot through all

the NF settings and see what's what.

 

Thanks all

[jtangen]

To get the sharpest photos from the E3, here is what I do.

 

#1 - Always shoot RAW regardless of what Dpreview says. Oly's raw converter allows you to use tools not available for jpegs.

 

My in-camera noise settings are: NR=ON and Noise Filter = OFF.

 

For tripod mounted landscape shots, I manually focus using Live View at 10x zoom on the LCD. It allows me to dial in the sharpest focus. For those types of shots I don't trust autofocus.

 

Having the Noise Filter set to OFF allows me to capture the sharpest image possible. It also allows me the choice to apply any of the Noise Filter settings via Oly Master/Studio if I think the image needs it. If you post process in any other program, they all seem to apply what is equal to the highest noise filter setting in Oly Master. So you they will always give you a softer image.