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Keeping Moiré To A Mininum

September 2, 2015

Introduction

One of the most basic problems which can show up in an image is an effect where a photographer has aligned himself, his lens and camera, and the subject/object he's taking an image of...in just the right combination to where a pattern will appear on the image. This pattern is referred to as moiré.

Moiré is one of those issues which has been around not only since film was available, but ever since the humans had two eyeballs. Moiré is around us all the time. A few examples are the screens on the windows of your home. If you take the time to look at them from different angles, you'll notice at a certain angle, a pattern appears out from the screen...then goes away when you move ever so slightly. When you visit a zoo or some wildlife area where fine screens are placed overhead to prevent birds or other critters from getting out, you will also see a pattern when you move around under it. What's happening, is a situation where the resolving power of your eyes cannot define the small details from a certain angle of view when they observe patterns which are overlapping each other.

This experience happens with your camera sensor as well, and there is probably no difference, except when moiré is captured within an image, you have more time to look at it and notice what the effect is doing to your photo.

Does Light Effect Moiré?

Yes. It most certainly does. Frown on any theoretical implication it does not. Since we're discussing photography, light has everything to do with images, and to exclude it from a list of attributing factors...would be somewhat uninformed of why patterns exist at different angles. Reflection has a lot to do with light intensity (just as much as the pattern itself), and when you increase the intensity of light, you increase the potential for more reflection of that light off of objects. Additional reflection is related to additional potential for moiré because light is bouncing off the object and into your eyeballs (or as we're discussing here, a camera sensor).

Since I just mentioned eyeballs, when you look at your subject through your DSLR's viewfinder, you may not notice moiré when the camera's sensor actually DOES. Why? Once again, it has to do with angles. Our eyes shift back and forth, up and down within the camera's viewfinder, and our eyes will unintentionally look for the sharpest image — free from focus distractions. This is an observation on my part, and this will depend on the person, but I've noticed myself I tend to easily forget what I just saw only milliseconds earlier. And what I forgot was a particular angle which projected moiré. Our brains tend to filter out parts of images that are imperfect and replace those parts which it thinks are more pleasing to see and/or replaces those parts with similar experiences from our past.

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Our human brain is amazing, indeed. However, it can lead to some confusion when we take a picture and view it within our image editor, because our image editor displays the image without (or mostly, anyway) prejudice. And then we wonder why a particular pattern is seen now when we view it on our computer, but it wasn't when we were taking the picture.

Sensor Resolution

Just when you thought you figured this out, there's another factor to take into consideration: sensor resolution. If the imager on your camera isn't matched to the resolution of the subject you're capturing...the imager itself will record a moiré image. This is going to be a learning experience for every camera you purchase as technology evolves so fast. However, the good news is resolution of imagers gets better every year, and companies like Canon and Nikon are very knowledgeable of these issues, and are continuously at work to give you and I a better imager which can record the most smallest of details within an image.

Reducing Moiré

If you're a professional photographer, enthusiast shooter, or just somebody who takes images on a regular basis (and are familiar with the settings on your DSLR), the following suggestions won't be difficult to understand — and you might have used some of them already. In any case, here are the following tips which should help you.

• Change Your Shooting Position

If you've been taking pictures for even the shortest period of time, you'll understand that moving your camera at various distances to and from your subject helps greatly in getting the image you want to capture. With the view modes on most DSLRs, you'll be able to compose an image, review it, and recompose it if you see any patterns present.

• Stop Down Your Lens

Most of the time, you won't be taking a picture at f/1.4. Most images I see, and have taken, are at f/5.6 to f/16. Why? Because your depth of field (how much of the image appears to be in focus) is greater when you stop down your lens. Most photographers want most parts of the image in focus for later editing. If your specialty is portraits, then you'll probably not want a large DOF, but this ok. Using the other alternatives mentioned here will certainly help.

• Adjust The Light Intensity

Whether it's coming from your studio lights, flash, or some other source, the light intensity on your subject is also a factor when reducing moiré.

• Invest In Lens Filters

Lens filters can either help you take a great image...or hinder it. Be sure to get a high quality filter that is up to your standards of photography, but also, up to the standards of the lens you own. Why put a $20 filter from a barely-known name on your $1000 lens? Having a good collection of various filters such as circular polarizers, light intensity filters to keep the bright sun from reflecting off your sensitive lens elements, etc., will reduce moiré.

• Dust Off Your Lens Hoods

If you're like me, lens hoods can take up a large area of the camera bag...and so they are left at home in a box. However, those simple accessories which are included with your lenses can also present an opportunity for you to avoid moiré.

RAW Image Editing Can Reduce Moiré Patterns

For Nikon users, Nikon does mention on their website when you experience moiré, it is much easier and more efficiently removed if you have an NEF (RAW) file to manipulate with Nikon's own software (or some other image editor such as Photoshop CS with their RAW converter). This is certainly contingent on the type of image (your subject), how much moiré is present, and how many areas within the image exhibit moiré. This can get very complex, but the point is, if you have more information to edit (more image data), then you'll have a greater chance of removing imaging effects without much damage to the image itself. In this case, a RAW/NEF image file, is a good idea to have around for editing. So, if you have your DSLR set on only compressed images to save space...you might want to reconsider setting your DSLR to recording RAW images as well. Why not. Memory cards are cheap enough, so there isn't much of an excuse, other than "...but it takes up so much space on my computer."

For Canon users the same word of advice would apply. And come to think of it, anyone who uses a RAW file. If you absolutely do not foresee the possibility in your photographic future where you will need the additional image information, and only want some Point N' Clickers to share with friends from your weekend warrior adventures, this is fine. Have and knock yourself out. And with the capabilities of and storage capacities of cameras, you could store thousands of images on a single card. I would suggest taking advantage of your DSLR's user profile settings so you can easily switch from Fun Mode to These Might Be Edited Mode. For Nikon DSLRs, you have U1 and U2 on their enthusiast level DSLRs (such as the D750), which includes the somewhat recently announced, 24MP Nikon D7200.

In Closing...

In this article, we've discussed a few methods of reducing moiré and also brought into the discussion, the human factor. Our own prejudiced visual perceptions can be an obstacle if we're not careful. If taking pictures with the intent to keep them is the goal, having as much information recorded at the time the image was taken (i.e., shooting in RAW), is definitely a wise choice.

Taking pictures is often a delicate matter. Moiré will never be theoretically taken out of the possibility of being in our images, but what we can do, is take certain measures to reduce the chances of it ever appearing. Being aware of it before we begin shooting, during our image taking, and identifying it in our RAW image editors post-processing, can we almost eliminate the potential.

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