Moire Pattern

That could be fixed very easily in an image editing program. Do you have one that you use?

Yes April. I have Elements 13 but barely have figured out how to use the basics in it. Any pointers would be appreciated.

Are you familiar with layers and masks?

it should print. unless you paint it on something totally smooth and flat, we will see the canvas.


---Mike Savad
MikeSavad.com

Have no idea what those are April. Sorry. And Mike, will the moire pattern show on the print when it is printed? I have had to photograph paintings over and over because of this pattern. Sometimes it is so obvious that I can not use the photograph.

Would anything here be printed in halftones where that would be a problem? I know most inkjets don't use what we think of as halftones—so much so that if you want to print in a traditional halftone, you have to download something like ghostscript.

Theoretically a canvas, having a regular, nearly 90 degree weave, could be a problem if the halftone were of a frequency and direction to create one. However, paper CMYK halftone organizes itself around what to me looks like a series of interlocking shapes. So, while one "film/screen" (color) might have a slight moire, the other colors could hide it if they're at an angle or frequency to do so. T-shirt screen printing process is often too course to pick up the fine pattern of the canvas anyway. But there has to be an old Gutenberg guy/gal here who would be able to tell you more one way or another.

This might help but you probably found this article already:
Frequency vs. Amplitude modulated halftones, configurations, etc: https://en.wikipedia.org/wiki/Halftone

Phyllis, because it's only the black portion that is very noticeable, I would suggest just adding a solid very dark gray or black layer over the photo and masking out the portion with the tiger. This video explains the process. It is actually very simple.

http://tv.adobe.com/watch/learn-photoshop-elements/layer-mask-basics/

Change the blend mode of the solid gray/black layer to multiply or linear burn and adjust the opacity until you get it how you want it. You don't want to eliminate the pattern completely, since you can still see it in the lighter areas. This is simply an easy way to tone it down in those dark areas and make it not so readily apparent.

patterns show as the image is compressed and the compression tries to make sense of the dots. it will also show up more on different screen sizes. up close i don't see an issue. though it might look funky on different screens.

---Mike Savad
MikeSavad.com

Oh, good point, Mike. I was thinking moire and therefore prints. It's kind of like the bad old days of 256 web safe color gradient dithers, right?

i was thinking more like each screen will show it differently depending on size and dot pitch. combine that with the intense compression the images get, and you get moire from that.

like trying viewing it on a phone or someone else's pc, it will look different. on mine i see faint horizontal lines.

---Mike Savad
MikeSavad.com

So you would remove the pattern then? Like they did in the first part of http://photo.stackexchange.com/questions/23445/what-is-the-best-way-to-remove-texture-from-a-scanned-textured-photo-paper or http://www.tipsquirrel.com/smoothing-texture/?

To understand this issue, first and foremost you need to understand the cause of moire. It's caused in nature/mathematics when the distance of one repeated pattern is close to the length of another repeated pattern. Thus, if you fold a piece of cloth onto itself, and they aren't in perfect alignment, you get regions of constructive interference and of destructive interference, much like a diffraction pattern. So you can see in not only in lightness and darkness, but also in color information. It's extremely easy to get moire effects in printing, where pixel or halftone size are one such pattern in themselves, and interact with any pattern in your image which is of similar size to the pixel size. What's amazing is that you don't see it more. Digital cameras, and digital editors use software techniques, such as anti-aliasing, to help minimize such effects. Almost every digital camera includes a software filter which automatically works to reduce moire patterns in your images. Otherwise, you would see them everywhere! (For example, where pixel size is close to the thread count in an image.)

You can buy a few specialized cameras, like the Nikon 700e (If I recall properly), which do NOT have the anti-moire filter built in. I believe the new high resolution 50mp camera has the ability to set the software filter on or off. This keeps the filter from degrading resolution. (If you've seen me discuss resolution in other threads, you will recall me claiming that all filters "mess with" the original image, thus degrading resolution. This is true of the anti-moire software in your camera. In the new 50mp canon 5D (model_number?), I believe, you can turn off anti-aliasing, and this (and perhaps other options) will tend to make moire more noticeable, I suspect, but also to increase image resolution.

So the first thing to be aware of is that filters which reduce moire will tend to degrade resolution.

Second, if the image contains innate moire, that effect may differ as you change the pixel size resampled pixel size, in an image. Because there are so many potential variables, my suggestion is to experiment with possible related filters, with a careful eye towards how the filters affect both moire and resolution.

Third, printing can introduce an additional layer of moire effects, since printing has its own visual wavelengths, arising from the printer resolution. Inkjets have an inherent pixel size related to the paper used and the actual ink jet spray hole dimensions and spacing. Half-tone printing introduces yet another set of visual wavelengths which can produce strong moire effects. Likewise, silk-screen printing will produce strong moire effects. These can be interesting, pleasing, or hideous. Proceed with caution!

I knew this would be too complicated for me! LOL

Gregory, thank you for the info. You must have had experience with shops using high tension screens. I've never had the privilege myself. What did you have done?

Edit: I'm genuinely interested since experiences shared help shed light on how to prepare one's work. I'm not speaking about actual separations but how you would evaluate something as printable and what will and will not print in your opinion.

Are you seeing moire in the original file when viewed at 100% or are you just seeing it on the reduced image on the website. BTW, I'm not seeing any moire while viewing on a 1920x1080 monitor. Just seeing the texture from the canvas.

Interesting thread-Guess I'll have to recheck one of my images that I was running off for a gallery-Thought my ink was low or I had to change the paper I used in the printer as that has happened before and that seemed to resolve the issue. But if it is imbedded in the image,as I believe it once was, I ran it through a paint program in paint shop and do remember that resolving that issue at that other time- Sometimes this stuff just gets so confusing, but checking at 100% does at least help discover the source a lot quicker.

I made a copy and just increased the contrast. You have plenty of latitude with your black level. You can darken the blacks without changing the tiger too much. That would be my simple fix. I don't know much about computers either!

I don't see any moire either, just canvas texture...maybe this is your monitor Phyllis and not the images or the cameras. It looks perfect to print.

I agree with Melissa - that's not moire as I understand the term, just a case of a good photo showing exactly how the original looks.

I donīt see any moire, too. If you donīt see something on your original file at 100%, there should be no problem.

Maybe JC can have a look at it. He can see the original file, too. (But maybe then, everybody wants their pictures reviewed by him ... 😎)

I'm not seeing moire, I see the canvas texture.

My related experience is that I did some part time offset printing for my church, where graphics often require half-tones, and I did some hobby work with silk screens, sometimes involving half-tones in that process also. Moire effects can easily happen in both environments, and could be "interesting", or merely distracting. I also did a little work with graphics in the early days of the PC, and early graphics images there typically had a lot of moire effects on fabrics, for example. On the other hand, using compass and ruler and ink, I made a lot of drawings designed to create geometric art, some of which had purposeful moire effects.

Of course, knowing physics and mathematics gave me an appreciation for wave phenomena, such as optical diffraction gratings, standing waves, and interference patterns.

One thing I didn't mention before is that the pixel size of your image and the pixel size of the screen can also produce moire effects, which are NOT in the image itself. I don't see this much (if at all) any more, so I wonder if digital monitors or JPG display algorithms in web browsers have software to minimize moire from this cause.

Greg, I admire your dedication! I would think screen printing beyond casual experimentation. I'd love to chat to see what you've tried regarding wave pattern, too. I guess the canvas pattern had never been an issue with the shops here since the weave was usually too fine to get picked up by anything but the 300's and even then if it was simulated process, the effect would be lost. If the pattern were a problem, turning the whole image 1- 5 degrees usually fixed it (even now I feel compelled to avoid anything set a perfect horizontal or 90 degrees).

It's nice to have the physics and math to back up the visuals, too. I bet you laugh when someone starts mentioning how they'll never use the knowledge in the "real" world.

I thought the screen dither issue was called something else, but yes, I think there are compensations for graphics as much as there are for text but am not sure if it's all done with anti-aliasing.