In this quick article, I will talk about how to avoid moiré if your camera is not equipped with a low-pass / anti-aliasing filter, or if it has a special low-pass filter like the Nikon D800E that is also prone to moire. Moiré can be quite painful to deal with in post-processing, so it is best to avoid it in first place. Below you will find a list of steps you can take to avoid moiré while shooting patterns.
- Analyze patterns in your images on your camera’s LCD at 100% view – while looking at your images on the camera LCD at 100% view can be very inefficient and time-consuming (especially on the Nikon D800E with its massive 36.3 megapixel images), if you are shooting anything with repeating patterns, you need to know whether there is moiré in your images or not. Looking at the thumbnail on the LCD might not reveal moiré, so you will have to zoom in to see it. Very strong / nasty moiré might be visible even at 50% view or less, while you will only spot mild moiré at 100% pixel level view. If you see moiré and want to avoid it, proceed to step #2 below.
Quick useful tip: if you own an advanced Nikon DSLR like Nikon D300s or higher, you can set the multi-selector center button on the back of the camera to instantly show 100% view without having to press the zoom button several times. You have to enable this feature here: Custom Settings Menu->Controls->Multi selector center button->Playback mode->Zoom on/off->High magnification. Once set, you will be able to zoom in to your images at 100% by simply pressing this button in playback mode.
- Change camera to subject distance or adjust focal length – if moiré is visible in your image, the best thing you can do is change the distance to your subject. You can either physically move closer or away from your subject, or you can zoom in/out with your lens. Remember, moiré only happens when the pattern you are photographing exceeds sensor resolution, so all you have to do is move to a safer distance. Sometimes this means moving just inches away from your subject.
- Adjust focus to a different area – while this is not always practical, adjusting the focus a little away from the patterns will remove moiré.
- Change the angle of the camera – simply changing the angle of the camera a little can completely eliminate even very strong moiré patterns.
- Stop down the lens to f/11-f/16 – when lenses are stopped down beyond a certain aperture (depending on the lens and the sensor size), an optical phenomenon known as “diffraction” kicks in. Diffraction effectively reduces resolution, which also eliminates moiré. While I would personally avoid doing this, if you cannot change your subject to camera distance or adjust your focal length for whatever reason, this technique surely works.
If you did not do any of the above and ended up with an image that has visible moiré, then your only option is to try to fix it in post-processing.