Moire question Sigma50/D880e.

[David Anderson]

I've just done my first proper shoot with the new Sigma 50 1.4 Art on the 800e and have some serious moire in it.
It's the first moire of any note I've seen from the 800e so I have to ask, how much would the lens have to do with it ?
The shot (I can't post it here) is a group of 10 people in shaded light and the moire is in 4 of the shirts that are tightly striped and blue.
Obviously, the shirts are the actual cause, but I haven't seen moire like this since the first Kodak V series backs..

[bjanes]

I've just done my first proper shoot with the new Sigma 50 1.4 Art on the 800e and have some serious moire in it.
It's the first moire of any note I've seen from the 800e so I have to ask, how much would the lens have to do with it ?
The shot (I can't post it here) is a group of 10 people in shaded light and the moire is in 4 of the shirts that are tightly striped and blue.
Obviously, the shirts are the actual cause, but I haven't seen moire like this since the first Kodak V series backs..

It could be due to the lens, but this is not a defect in the lens but rather a tribute to its resolving power. Moire occurs when there is significant resolution beyond the Nyquist limit of the sensor. Shooting at a smaller aperture than you used for the shot would reduce the moire.

Regards,

Bill

[fdisilvestro]

Use a less sharp lens 

Well, jokes aside, as Bill said, this is a case where the lens ouperforms the sensor. In the absence of an AA filter, you need something that acts as a low pass filter such as using a low aperture.

Another possibility is to try different raw converters (I suppose you captured raw). For instance, rawtherappe offers 10 different demosaicing alorithms. Sometimes the reduction of moire is at the expense of sharpness, but you can have two versions of the image and mask the troubled areas from the sharpest.

Regards,

[kers]

Yes it is a sharp lens !
I don not know what raw converter you used, but ACR for instance gives a lot more moiré than Nikon's NXD. I have not tried many others...
So you can benefit from chosing a different converter.

[Some Guy]

Actually, I rejoice if I see moire as I know the camera and lens AF system nailed it.  I own the Nikon "Holy Trinity" series of zooms and I rarely see it, nor with their 105mm macro either.  I went out and searched screens, netting, fabric, and it rarely shows up.  Stuff just ain't sharp I guess, even though they worked on it and meets specs.  Just be glad you didn't spring for a $4,000 Otus lens!  

I believe Nikon's Capture NX-2 addresses some of it (My 1st line of post-processing NEF files out of the D800E.), and Lightroom to some extent.  Photoshop has ways of dealing with it too:  https://photographylife.com/how-to-remove-moire-in-photoshop

There are also times I see it on the screen, but zooming in or out on the screen changes the pattern and printing may not even show it either.  Very odd why that happens.  

Some mentioned some outfit makes a screw on anti-moire filter too that addresses it by adding astigmatism to the optics. Here: http://recordingsofnature.wordpress.com/2012/09/25/dslr-antialiasing-filter-sharpness-charts/

Good luck.

SG

[HarperPhotos]

Hi David,

I’ve been using a Nikon D800E for most of my work and when I do fashion images I use the Nikon D800 instead because of the moiré problem with D800E.

Yesterday I did a shoot of my thirteen year old niece and ten of her girlfriends in the studio to celebrate the end of there school year as she starts high school next year.

I have bought the Nikon D810 so I decided to try it out cause it has no AA filter at all.

The girls where wearing all sorts of clothing and I used my Sigma 35mm and 50mm Art lenses as well my Nikon 85mm F1.4 G lens all at F8.0.

I shot 420 frames and there was not one bit of moiré in any of the  images and I was looking hard for it. So I think the people at Nikon have done some sort of magic in there new processer as I know if I have used my now sold Nikon D800E moiré would have been there.

I have a large fashion shoot in the new year which I would normally use the Nikon D800 but I think I will use the Nikon D810 first and if there isn’t any moiré the D800 will also be going on EBay.

Cheers

Simon

[David Anderson]

Thanks for the replies - they're a big help.
FWIW, I shot raw and then converted in ACR. (I just use Bridge)
I fixed the moire with some photoshop work after conversion and it looks ok now, though I won't be entering the shot for any prizes - lol


Harper, nice idea for a shoot...

[ErikKaffehr]

Hi,

Stopping down to f/11 - f/16 would be able to eliminate moiré. Essentially by reducing sharpness but that sharpness can be regained using good sharpening.

ACR is about the worst converter regarding moiré, I hope they fix that issue with the next generation of the processing pipe line, now that more and more sensors lack OLP filtering.

But, aliasing is really impossible to remove, just possible to hide. OLP filtering on sensors is intended to defeat colour aliasing on Bayer sensors, which almost all sensors happen to be. It is possible that gapless microlenses can reduce moiré tendencies.

The best way of getting rid of aliasing problems is really smaller pixels, as discussed here:
http://echophoto.dnsalias.net/ekr/index.php/photoarticles/78-aliasing-and-supersampling-why-small-pixels-are-good

Best regards
Erik

Thanks for the replies - they're a big help.
FWIW, I shot raw and then converted in ACR. (I just use Bridge)
I fixed the moire with some photoshop work after conversion and it looks ok now, though I won't be entering the shot for any prizes - lol


Harper, nice idea for a shoot...

[HarperPhotos]

Hello,

Here another image using the Nikon D810 and Sigma 50mm F1.4 Art lens at F8.0.

From past experience if I had used my old Nikon D800E there would have been a good chance of moiré in the denim shorts.

All my images are proceeded with ACR.

Cheers

Simon

[David Anderson]

Stopping down to f/11 - f/16 would be able to eliminate moiré. Essentially by reducing sharpness but that sharpness can be regained using good sharpening.

That's a good idea - I'll keep that in mind next time I shoot something with the possibility of bad
moire..

[Herbc]

I understand Sigma offers a usb thingy to work with the lenses, although I think it is for focusing issues.  Anybody have experience with that?

[Some Guy]

I understand Sigma offers a usb thingy to work with the lenses, although I think it is for focusing issues.  Anybody have experience with that?

Yes!  Just get one!

The AF system is not linear with distance.  The Sigma USB puck allows one to tune it in four distance zones, or whatever ones you want to use it in.  Mine (35mm) has a weird -13, -9, -3, +1 in AF tuning distances with one body, and it is different with another body.  Very odd, but it helps to tune the things.  Nikon only allows for one setting in their menu, and Canon allows for two with their zooms.  Not enough, and I doubt if their techs tune it any better than the owner could do it.

Nikon should make the same gizmo for their lenses, imho.

SG

[bjanes]

Stopping down to f/11 - f/16 would be able to eliminate moiré. Essentially by reducing sharpness but that sharpness can be regained using good sharpening.

ACR is about the worst converter regarding moiré, I hope they fix that issue with the next generation of the processing pipe line, now that more and more sensors lack OLP filtering.

My tests with the D800e and Zeiss 135 mm f/2 ApoSonnar (another very sharp lens) confirm your observations. ACR was the raw converter. These results show primarily aliasing rather than Moire, but the two phenomena are manifestations of the same process. At f/11, there is still some alaising, but it is largely gone at f/16. Deconvolution sharpening with Focus Magic restores much of the lost contrast and resolution down to Nyquist (shown by the circle). The images must be viewed at 100% to avoid down sampling aliasing. Resolution as determined by Imatest and without any sharpening is shown in the graph.

f/4


f/11


f/16


f/16 followed by Image Magic sharpening:


Resolution


Regards,

Bill

[Some Guy]

My tests with the D800e and Zeiss 135 mm f/2 ApoSonnar (another very sharp lens) confirm your observations. ACR was the raw converter. These results show primarily aliasing rather than Moire, but the two phenomena are manifestations of the same process. At f/11, there is still some alaising, but it is largely gone at f/16. Deconvolution sharpening with Focus Magic restores much of the lost contrast and resolution down to Nyquist (shown by the circle). The images must be viewed at 100% to avoid down sampling aliasing. Resolution as determined by Imatest and without any sharpening is shown in the graph.
....
Bill

Bill, have you tried using Nikon's RAW converter rather than ACR?

SG

[ErikKaffehr]

Hi,

Just to say, aliasing artefacts is something that it is possible to mask but impossible to get rid off. The only real cure is improved sampling:

• Smaller pixels
• Area sampling

Both reduce perceived sharpness at the pixel level but improve the quality of the image.


Best regards
Erik

Bill, have you tried using Nikon's RAW converter rather than ACR?

SG

[David Anderson]

My tests with the D800e and Zeiss 135 mm f/2 ApoSonnar (another very sharp lens) confirm your observations. l

Thanks for the samples Bill - that very interesting.

I wish there was an AF version of that lens, I would have one in a minute...

[Abe R. Ration]

I only have the lowly 24MP Sony A7, and in spite of it having one weak AA-filter on top of the sensor it still provides slight moiré at f/16. The finer pixel pitch of the 36MP of D800e helps, but on the other hand the D800e has no AA-filter at all. Some samples at f/2,8 and f/16 with and without simple deconvolution (at 24MP). Much more pixels are needed.

[Bart_van_der_Wolf]

I only have the lowly 24MP Sony A7, and in spite of it having one weak AA-filter on top of the sensor it still provides slight moiré at f/16.

Hi,

The sensel pitch of the A7 is approx. 5.97 micron. That would set the absolute diffraction limited resolution (MTF=0) for 555 nm wavelengths for an aperture of:
Aperture = (2 x senselpitch) / wavelength, e.g. (2 x 0.00597 mm) / 0.000555 mm = f/21.5 , as explained here.

That would make sure that even without an optical Low-pass filter (OLPF) there could be no moiré from detail beyond the Nyquist frequency. Adding an OLPF of some strength would allow to use somewhat wider apertures and let the interaction with residual lens aberrations limit the resolution enough to avoid moiré before reaching the diffraction ony limit.

The finer pixel pitch of the 36MP of D800e helps, but on the other hand the D800e has no AA-filter at all.

That smaller sensel pitch would shift the absolute diffraction limit on resolution (and thus eliminate moiré) for the D800E to:
Aperture = (2 x senselpitch) / wavelength, e.g. (2 x 0.00488 mm) / 0.000555 mm = f/17.6

Better lenses add fewer residual aberrations and will allow to achieve (more) moiré even when close to these absolute diffraction limits, where as lesser lenses will prevent moiré already at wider apertures.

Cheers,
Bart

[ErikKaffehr]

So, in this case More (pixels) is Less (moiré) :-)

Erik

Hi,

The sensel pitch of the A7 is approx. 5.97 micron. That would set the absolute diffraction limited resolution (MTF=0) for 555 nm wavelengths for an aperture of:
Aperture = (2 x senselpitch) / wavelength, e.g. (2 x 0.00597 mm) / 0.000555 mm = f/21.5 , as explained here.

That would make sure that even without an optical Low-pass filter (OLPF) there could be no moiré from detail beyond the Nyquist frequency. Adding an OLPF of some strength would allow to use somewhat wider apertures and let the interaction with residual lens aberrations limit the resolution enough to avoid moiré before reaching the diffraction ony limit.

That smaller sensel pitch would shift the absolute diffraction limit on resolution (and thus eliminate moiré) for the D800E to:
Aperture = (2 x senselpitch) / wavelength, e.g. (2 x 0.00488 mm) / 0.000555 mm = f/17.6

Better lenses add fewer residual aberrations and will allow to achieve (more) moiré even when close to these absolute diffraction limits, where as lesser lenses will prevent moiré already at wider apertures.

Cheers,
Bart

[NashvilleMike]

I'm arriving late to the holiday Moire party but I essentially agree with what everyone else has been saying plus a few thoughts.

I shoot with a D800E although I've also used the 800 and 810. A seriously sharp lens (either of the Sigma art primes, the Zeiss apo sonnar, the Otus) will definitely allow moire to be seen by nature of their exceptional resolution. Unfortunately I can't say the D810 solves the issue either: I've seen moire with a D810 and both a Sigma 50 art and an Otus 85, so it's not exempt. Moire often can also be tricky - at one particular combination of aperture, lighting direction, lens selection it occurs but a slightly different angle, aperture, etc and it can be mitigated - at least in situations where you're not at the absolute sharpest aperture of the lens.

The solutions are generally to try stopping down first - I see F/11 as sort of a "moire filter" - doesn't always take care of all of it, but it helps and if I'm shooting a particularly tricky piece of fabric in the studio (say a mesh of some sort), I'll take off the Sigma 35 or 50 art and use the Nikon 24-70 as a replacement. The 24-70 is still a sharp lens, but not in the category of the two Sigma primes (which in the subject distances associated with studio work are about as good as it gets), and that slight drop in resolution usually solves, or at least, significantly reduces the problem.

I should note I don't use Adobe raw conversion products, since raw conversion does play an impact.

At the end of the day I think it's a case of learning ones tools. I shoot in the studio quite a bit so by now I kind of instinctively "know" which lenses and fabric combinations are likely to give me moire problems and I'll use one of the methods described (stopping down, lens change) when I am going to be using them.

-m