How to 3D Print a Photo: Lithophanes 101

If you are looking for your next 3D Printing Project, you need not look any further. 3D printed photos, also known as 3D Printed Lithophanes, are an extremely unique and creative application that is sure to “WOW” most people that come across them.

What is a Lithophane you might ask? Well, a Lithophane is a 3D representation of a photo that can only be seen when illuminated from behind. A gray-scale representation of the image is created and then depending on the color it is then converted to a calculated 3D printed height. This allows a specific amount of light to shine through. Darker colors block more light and the opposite relationship stands for lighter pixels. Each pixel in the image undergoes this process and a very unique art piece is created.

What are these good for? These make wonderful gifts for any occasion. If you’re like me, I like to give unique custom gifts that are a little more personal than the norm. This is the perfect way to achieve that. I made a few mother’s day gift for my friends this year, and this Christmas people are sure to receive some of these from me! Plus, it’s a cool way to highlight 3D printing which is not familiar to everyone.

This instructable is designed to give you one path (of many possibilities) to create and 3D print a photo. I plan on going over; the basic considerations of choosing a photo that will give you the best results, sizing an image to prepare it for STL creation, one software example of how to convert the image into an STL, and different ways to light and display the 3D Print.

Step 1: Selecting the Right Image

There are few things to consider when you are picking an image to 3D print. Not all images are going to come out as good as others. Through my experience I feel that there are three main things to keep in mind:

1. PICTURE RESOLUTION

This is a semi-critical metric to keep in mind when choosing a picture. You want to make sure the picture resolution is good enough to obtain the results you are looking for, but you don’t need to have a huge resolution picture for a small piece. I wouldn't recommend picking an image that is 50x50 pixels and expect to print a 8”x8” litho and have anything that resembles a decent image come from it! On the opposite side, there is no need to have a 10 MP image to print a 2”x4” piece.

I have included two excellent links below that give great recommendations on picture re-sizing and cropping to get the best results.

The first link is a good reference on “pixels vs. print size”. I personally refer to this to crop my images almost every time. It always seems to get the image into the exact size I need for STL creation. (The 300dpi is what I normally stick with)

http://www.myphotoshopsite.com/tutorials/level_3/3...

The second link is a “Quality vs. File Size” metric table. It breaks down the necessary file size of your photo versus the quality of your print size you intend to print it in. From my experience, using “very good”, “excellent”, and “photo quality” from the table is more than sufficient to achieve great results.

http://www.urban75.org/photos/print.html

2. COLOR CONTRAST

Picking a picture that has a variety of color contrast is a good metric to keep in mind. A dark picture, or one that has a lot of deep colors next to each other, might make the details in the print look a little blurred together and hard to see. This really will be obvious on printers with lower resolutions. Luckily, the printer I have access to has a great resolution so I am able to get away with a little more detailed and darker pictures. Check out the western picture I included above. The walls, clothing, and fireplace were all pretty dark and I can imagine without a 28 um layer height it might be hard to distinguish between them. Now, lets look at the 3-step picture of the father and son. This shows the original picture, the lighted litho and unlighted litho picture. The original image shows a good combination of light and dark colors. It my opinion, it generates an excellent final product! (That’s with taking my personal bias out of it because my new born son is in it! )

So the main take away it that it’s a good practice to be mindful about color contrast when selecting your picture, but it may not be as critical as you would think (depending on your printer quality).

3. 3D PRINTER

The main factor that plays the biggest role in the litho quality is the 3D printer you intend on using. There are a lot of you out there that have your own 3D printers sitting on your desk or setup in the garage. Unfortunately, some of these machines don’t have the accuracy and precision needed to take a super detailed image and create a super detailed litho like the ones shown above (which was printed with an Objet30 at 28um layer height resolution). BUT, these machines can still create some pretty awesome results for simple and none-complex images. Most portraits and highly contrasted color images will yield the best results no matter what printer you use. More details are described in Step 3 where thickness height of the Litho can affect your final quality. This can be used to increase the quality of the litho for 3D printers with less resolution.

Step 2: Picking a Finished Size

Picking your final application or purpose for your litho is a very important one! If you want to fit it in a frame with a backlighting option the final dimensions are needed in order to correctly size it. You do NOT want to convert the picture into an STL (using software options listed in next step) without being as close as possible to the final dimensions. Scaling a Litho STL doesn’t always work out the best. It can cause the image to become pixilated and distorted ultimately leading to a less-than-desired final product.

With this said, a “LITTLE” scaling down has never caused any major issue with the quality of the final product for me. For example, the software I use accepts integer values in millimeters for maximum feature sizes and if I am printing a 5”x7” final piece that would be a max feature width of 177.8 mm. Due to only integers being accepted, I create the litho with a 178 feature size and then use scaling to bring it down to 177.8 mm in my .STL prep software. I wouldn’t suggest scaling the picture up or down more than 1% of the original .STL file size. This is where the initial cropping of the original image comes into play. Make sure your math is right!

Step 3: Software Can Make or Break It

This is probably the most important step! Converting your Image into a lithophane is where everything can go wrong! If the correct settings aren't selected and/or configured for your 3D Printer than weird things can happen. After messing around with several different software applications (mostly free ones), I came across one in particular that made it VERY EASY! The majority of this section will go into the process on how to use this software, but before I dive into the details I thought I would list several different applications that can get the job done if you don’t share the same opinion on my selection.

1. Image to Lithophane – Browser driven, so no software has to be downloaded (My Choice)
2. PhotoToMesh – Huge flexibility and user control on .STL creation (cost money tho)
3. Customizable Lithophane (Thingiverse) – Browser Driven, so no software has to be downloaded
4. Photoshop CC 2014+ - Tutorial on how to use Photoshop plug-in to generate lithophanes.
5. 2D Image to STL Converter (Windows only)

The “Image to Lithophane” software is fairly new (released 1st version in Jan 2015). I stumbled across it a few months back, and once I figured out how to use it I haven’t looked at any other solution since. When you first come up to the “home page”, shown in Picture 1 of this section, you are prompted with a menu bar, a 3D view, and a horizontal profile selection bar.

1.) Selecting Your Image

The first thing you want to do is click on the “Images” tab in the menu bar. You should see something similar to Picture 2. This is where you will drag-n-drop (or select) your image. Once it successfully loads, you simply just click the image thumbnail that is now displayed in the dashed rectangular box and it will automatically bring you back to the “Home Page” view. Next, you want to select your profile from the bottom slider options. Each Profile has a set of options that you can configure, but for simplicity of this tutorial I am going to stick to the flat profile. Click and make sure it looks selected like in Picture 1.

2.) Image Settings

Next, we have a few settings that we need to configure in order for everything to render correctly. Click on the “Settings” tab and you should be prompted with something like Picture 3. First, we need to setup the “Image Settings”. Picture 4 shows the default settings. The only thing that I change in this menu is the Positive Image – Negative Image slider switch. I make sure it is set to “Positive Image”. Unless you want a negative of your picture than you don’t want to change anything. I am sure something cool can be created with the right image.

3.) Model Settings

Next we want to configure the “Model Settings” which should look something like Picture 5. These are the main settings for configuring the creation of your lithophane. The three settings I normally change every time I use this software are:

Maximum Size – This is the value that determines your biggest geometry (length and width) size. The default is 100 mm. One note to be aware of, this feature can cause things to slow down on your computer because there is a lot of client side processing involved with the creation of the .STL. So I wouldn't recommend going crazy and trying to render a 12”x12” piece here. It may crash your browser!

Thickness – This is your total thickness of your piece. I normally leave it set at 3 mm. I have never had any issues with my printer not displaying details correctly. You can adjust this setting to lighten or darken the entire picture if you want. And sometimes you can get better detail out of the final print by doing this as well. For 3D printers with less resolution in regards to print height, this is where you can play around with the settings to see what works best for your application. I wouldn't make it too thick though because light does have to shine through your material for this effect to work.

Thinnest Layer – This is basically setting your white pixel value. Again, I very rarely change this from the default of 0.8 mm.

With my above settings, this gives a total print height of the lithophane of 2.2mm. With the printer I used that has a 28um layer height resolution, which gives me ~78 shades of grey to play with. I have still yet to see any details lost with this resolution, but I haven’t printed every combination imaginable… yet! ;)

The other settings to play around with in the model settings tab can give you more unique results. For my applications, I normally print with no border or base height because I put them in a shadow box with led back-lighting.

There are many different settings in the case of selecting a different profiles and I leave the fun and experimentation of those up to you. Please share your unique pieces in the comment section below for everyone to see. The possibilities and applications of these are limited only by ones creativity. I, myself, am working on ornaments and touch lamps using this same approach.

4.) Create and Download STL

Once the settings are configured you simply click on the refresh button on the left under the 3D rendering display box and it will automatically generate your STL in a few shorts steps. Once it is visible in the display box you can simply click download (to the right of the refresh) and pick your destination for it to be transferred to.

And that is it! You now have successfully created your STL and are ready to get your 3D print on! Dont forget to verify your STL with a repair and analyzer tool. Google search "Free STL file repair" and several free options should come up if you don't have this software easily available to you.

After STL mesh is created and ready for 3D printing:

For those of you that have your own printer at home, here are a few things to make sure that are configured correctly before you start your print.

1. Make sure you print the model solid (no inner mesh or honey comb structure). Without this, the whole concept behind a lithophane won’t work!

2. Print at the slowest speed possible that your printer supports.

3. Print at the smallest layer height possible.

Other than the above tips, I am not familiar with open source setups of a typical “home use” 3D printer. So I pre-apologize if there are any additional steps that I didn't mention above. I do know that slicing your model is critical, but I can’t begin to elaborate on this because the background knowledge isn't there for me! I guess there is still plenty more for me to learn in the future.

BONUS:

For the brave and adventurous, creating your own software to do this process is not completely impossible! This whole process can be another Instructable in its self, but for now I will just give a quick step-by-step description on how to do this. The process can be broken down into four main parts:

1. Converting image into a gray-scale representation. Wikipedia has a great breakdown on how to convert an image to its native gray-scale representation.

2. Inverting the image pixels to reflect the height of plastic accurately. We want the white pixels (RGB=255,255,255) to be thinnest and black pixels (RGB=0,0,0) to be darkest. As you can see from the RGB values above, that would not be accurately reflected without the inversion since the height is determined from the RGB value. Without doing the inversion of pixels you create a negative representation of the image. I personally have done this a couple of times and it gives a unique finish. With the right picture I can imagine something quite amazing could be created.

3. Creating the STL mesh from pixel color. This is probably the most complicated step. This part includes the sizing of the mesh which is important to the overall success of your design. The three key factors to consider when creating the mesh are; minimum thickness of the base, maximum thickness of the total design, and the X and Y final dimensions. For generating the code to create the actual STL you can reference the following Instructable where he gives an example that can get you started.

4. Check and prepare STL for printing. This can typically be done with secondary software or for free online. Some of the software I have used to create these STL files left holes and intersections that are nearly impossible to find without the correct software. Luckily I have access to Spaceclaim, and fixing these issues is as simple as clicking the “auto fix” button!

The rest of the details I leave to you. Perhaps I can find some additional time to do this one in more detail in the near future.

Step 4: Light It Up

This is the fun part! When your 3D print is finished and cleaned it’s time for the ooooh’s and awwwe’s to start coming out! Even after printing dozens of these, every time I put light behind it, my smile never shrinks and I get all excited like it’s the first time I have ever seen something like it! There are several ways to light them up. I will go over the two most common that I have run across.

1.) Using the natural light around us

Natural light is key! Sunlight works the best (in my opinion) for these pieces of art. Simply placing them in a window or near some sort of sunlight source you will see the image suddenly appear. This can be as easy as resting it against a window, or drilling a few holes in the corners and adding some suction cups.

This is the easiest way to show off your new lithophane. This method works great for inexpensive gifts and/or knickknacks that you may find yourself spreading across the house! I will admit, I do have my fair share hanging in “many” rooms in my house!

2.) Custom back lighting

For the little more advanced users, buying a shadow box,or other frame style, and putting some back-lighting behind it can allow someone to create a real work of art! There are two different types of back-lighting, direct lighting and edge lighting. The details on these I will leave up to you to research… there are pro’s and con’s to each. My experiences have shown that edge lighting might be the best (easiest) solution for lithophanes, but I am sure someone can come up with a unique and crafty way of diffusing the direct back-lighting across the print without having too much of a focal point.

I have found that a 12V LED flexible strip (or any other flexible LED strip of choice) works great and are fairly easy to get them wired up with a basic electrical background. Picture 1 shows an example of one of these setups! Just a standard 12V power supply was used. I cut the end barrel jack plug off and soldered the connector you see in the picture so that it connected directly to the LED strip flawlessly. Please check the polarity of wires before doing your final soldering. You don’t want to fry your LED strip right out of the gate and not get to see your brand new lithophane!

For ease of wiring you can go to Lowes. They have an easy kit that you can have setup in minutes. Take a look at it here. One thing to mention about this kit is that it comes with two 18” strips which are great for larger lithos like an 8”x10”, but you only need one strip for 5”x7”. You can use a universal 12V 1A power supply for the other strip and modify the jumper connector (comes with pack) by cutting it in half and soldering it to the power supply. This has worked great for me in the past when a quick LED solution is needed.

Also, you want to make sure the back of the frame is white to help disburse the light inside. Simply adding a white piece of paper will work, or you can spray paint the entire inside of the frame gloss white. Just make sure your lithophane and LED strip doesn't get any over-spray on them in this process!

I have tried coming up with a battery powered option, but the 12V voltage requirement has made some of these solutions quite undesirable. Eight “AA” batteries on the back of a frame look a little bulky. I have entertained the idea of putting a rechargeable battery like a Li-ion battery or something similar, but the price associated with having the correct setup puts it a little higher than I want to spend, and it would still have to have a charger lying around depending on how often you have it on display! Maybe throwing a timer and motion sensor circuit on it would be cool. That way the LEDs will turn on when someone walks by and then turn off after a set amount of time to save on battery life. The possibilities really are only limited by ones creativity.

Something I have NOT done, but think would be an awesome project would be to integrate some neo-pixels or RGB LED strips into a display that gave the user the ability to fade and change the back-light in different areas. This could allow someone to shade a beach picture with blue on the water and red or yellow for the sun (sunset). This could lead to an incredible effect if done right.

Step 5: Conclusions

This is my first attempt at posting an Instructable! I decided to take the leap and create one that is something I know a significant amount of information on and have lots of experience with. My hopes are that I will inspire at least one person to give this a shot. It really is something that I think is quite incredible, and I still haven’t met anyone that doesn’t think it is amazing when you flick the power switch on and magically a picture appears!

Please vote for me in the 3D Printing Contest and Mind For Design Contest. I would love to try different materials and printing processes with lithos. I am very limited (less than 4”) on height with the printer I have access to, so having a printer like the Rostock max would allow me to experiment with lamp bases and other vase like shapes along with other colored materials.

Also, if this process is something that seems out of reach or you just don’t have the time, but LOVE the concept and want to buy one. My good friend, that has been generous enough to let me use his printer to make my own personal lithos, would be more than happy to help you out. All he needs is a picture, print size, and lighting choice and he will do the rest. You can contact him at:

[e-mail]

Thank you for taking the time to read through everything and if there are any further question please leave them in the comments section, and I will do my best to answer them in a timely manner! I look forward to seeing what others come up with and I hope you share them with us when they are done!