2D Photogrammetry for Fabrication and Design

August 22, 2017  •  Leave a Comment

In the course of my career as a Fabricator and Designer, I've learned that often the most challenging aspect of the job isn't mastering fine precision of CNC Machinery or even creative fixturing in order to finish a part. Often, the most challenging aspect (unless you have extremely expensive 3D scanning tools tools at your disposal) is getting accurate data into the computer to work from.

How many hours have I spent with a set of calipers, a measuring tape, and a notepad, only to find human error on a measurement or simply overlooked something? Even if I'm perfectly thorough, this process is time-consuming. During my time at Blue Seas Fabrication I was lucky enough to be able to use a Proliner to scan boats with - this provided excellent accuracy, and made design and fabrication of SeaDek much more efficient.

At West Coast Customs, we don't have a 3D scanning device in-house (from time to time we rely on the services of a 3D scanning company), so for the day-to-day digitizing of parts and materials, I've had to find some creative workarounds. This is where my knowledge and experience as a fabricator/designer intersect with my knowledge and experience as a photographer/cinematographer, and the results serve me extremely well daily even on large objects of 10' or greater. It is my intention to share those with you here and now.

 

Option 1: 2D Scanning.

This is quite straightfoward. For smaller parts, use a flatbed scanner, like the one on all-in-one printers that you sometimes get for free. This works remarkably well for scanning small, flat parts and for smaller templates. If needed, one can always scan something larger in pieces, then recombine them using added registration marks. Critical to this (whether a single image or multiple), is adding marks for scaling (see ex 1, 2).

Example 1: Cardboard Template for a custom Spoiler bracket.

Example 2: part 2 of same Cardboard Template. The marks on these are almost impossible to see - miniscule blue dots. Can you spot them?

The final product

In whatever CAD program you prefer, bring the images in and scale them based on your measurement points, and align them using the alignment points - these points can serve multiple purposes, I like to use registration marks that are also measurement marks. My preferred method is a dot surrounded by a circle of dots, as concentric circles are easy for the human eye to spot and align.

Once the images are aligned, draw your part, check your measurements, adjust as needed. Done.

 

Option 2: 2D Photogrammertry.

Scanning is great, but isn't always practical. breaking apart a large template can take a really long time, and the more tasks a human has to undertake, the more room for error creeps into the equation, which could easily cost time and money for materials. If the piece in question is something that someone has already worked a long time on, the results could be disastrous.

It wasn't long before I realized just how important it was to be able to gather accurate and repeatable visual data here at West Coast Customs. Initial efforts with mobile-phones and measuring tapes have been mixed at best, usually requiring a generous amount of grinding and/or bondo to make work, if indeed a revision and re-cutting isn't required.

My solution for this was to find a spot in the shop I could use pretty reliably for Photogrammertry using my camera. Below you will find a basic write-up and tutorial on how to do this yourself, should you feel so inclined.

The supplies and gear I used are as follows:

Sony A7r
Konica Hexanon 50mm f1.7 prime lens with adapter
One 1/4-20 screw (available pretty much everywhere)
Some 3/4" MDF (wood) and tools to work it
glue
a plumb-bob (any sort of weight and string will do)
masking tape
tape measure
either a clear wall or elevated position (in my case I used a catwalk about 15' above a clear section of floor)

The first thing I did was assess where I was likely to do most scanning. Since perspective distortion reduces the further a camera is from the object, I picked the catwalk, a level, elevated position some 20' above a nice flat even surface. It'd be pretty easy to use a wall or pair of walls for this - in my opinion the key to good photogrammertry is repeatabilitity, so ideally, choose a spot where you can install a fixed camera mount or at the very least, someplace where you can make marks for consistent image acquisition.

With my location chosen, I took my camera with fixed 50mm lens and measuring tape upstairs. Holding it relatively level, I measured how far out from the rail it would need to rest in order for the field of view to clear the catwalk. As I was not using leveling tools, I was generous in my estimate - about 15" from the edge of the rail to the base of my camera.

After that, I designed a simple mount to hang on the rail, while sitting square and flush. I used the lower rails as bracing, measuring the standoff difference, and overcompensating for it in my design with the intention of sanding to fit. Below, you can see the completed mount with my camera affixed. As a bonus, it looks like a goat. \m/

Next, I used a plumb-bob to find the center-point of my lens, directly below where it sits on the mount. With a marker in place, I used Adobe's Lens Calibration Tool and associated calibration charts to create a lens calibration profile for my camera and lens. For this purpose, I set the lens to f5.6 to ensure crisp focus across the entire field of view and still let in enough light to keep noise levels low.

Once I knew what was directly below my lens, I used a sanding block to trim down the lower portion of the mount until my mark below was dead-center of my lens. This ensured that the corners of the frame would essentially all be equidistant from the lens on the floor, further reducing perspective distortion.

Once a repeatable, level camera position had been achieved with a clear level space in the field of view, it was time to create a lens calibration profile for my camera. For this, I used the Adobe Lens Profile Creator Tool, a free download for Windows or Mac. Granted, this will require Photoshop or Lightroom to use your created profile, but a subscription isn't cost-prohibitive, and full demo-versions can be downloaded and used for a full month from Adobe's website. Following the instructions of this tool via the included PDF was not a simple undertaking, but absolutely worth the effort. Stock lens profiles are not nearly as accurate as can be achieved via a custom profile. Using a measuring tape, measure the dimensions of your field of view. Compare these dimensions in inches to the resolution of your camera images. This will allow you to find an approximate measurement of pixels per inch. My setup has a resolution of about 78 PPI. For my purposes, this is the right blend of precision with overall size capacity. Using our large-format printer, I printed a nice big lens calibration chart (for my purposes I used "Landscape JIS_B0 - 40.60 In x 57.30 In (Square Print Dimension 54 Pts, Version 51 x 73).pdf" from the included charts). Make sure you choose a chart that is large enough to cover a significant portion of the frame and has small enough checkers to give the computer good data, but not less than 20 pixels across.

Initially, I had planned to move the chart in the frame, but the software will NOT work if you do this (I discovered this the hard way) - you'll need to move the camera itself, so loosen the screw on the mount enough to pivot the camera from its position enough to take a series of images as per the instructions, and run your calibration profile creator based on them. Make sure to take enough images to avoid having to do it twice - I recommend 13. Below is an image of me setting the initial position. Technically, this is a selfie.


 

Once your calibration profile is complete. use of the setup is quite simple. Place the piece to be scanned, extend your measuring tape and lock it, laying it on top of or next to the part, check focus and f-stop, photograph the piece, correct the geometry of the image in Photoshop of Lightroom, crop and export, import to CAD, draw your part, check measurements, adjusting as needed, and you're done! Enjoy drawing parts from accurate visual data!

A custom door trim piece for a Camaro. Photographed, corrected, and drawn. The final part was dead-on.

 

A final note on photography equipment:

It doesn't have to be expensive to gather accurate visual data! Not at all! The lens I'm using for this I bought at a Swap-Meet for $6. Of course the higher-resolution and better build quality camera you use will help you gather MORE data, but even an old used inexpensive mirrorless camera with a garage-sale fixed focal length (prime) lens will absolutely do the trick. You COULD use a variable zoom lens, but I would advise against it if you are attempting to make accurate scans. Good Luck!


The Decentralized Library of Alexandria

June 08, 2017  •  Leave a Comment

I'm changing the way I publish digital media, you should too.

Lately I've begun publishing some of my work on "The Decentralized Library of Alexandria" - a unique, decentralized, peer-to-peer based distribution index. There's a lot of nitty-gritty stuff I could go over, but I wouldn't be able to explain it as well as the owners of the company. In any case, the important things other artists need to know are:

1. The cost to host and sell ANY sort of digital content is almost zero - right now, it costs about 10 cents per submission. You don't pay any renewal fees, subscription fees, or any of that nonsense, and bandwidth does not cost extra.
2. The uploads are permanent (though you can have them removed from the website's listing), and referred to as "Artifacts".
3. There are ZERO ADs. None. Zip. Zilch. Nada.
4. The system is coupled with a built-in copy protection scheme which permanently protects your artifacts.
5. You can accept micro-payments for content - as much or as little as you want! $.05 a view? No problem. $1 downloads? ok. Up to you, and you alone. The money goes DIRECTLY to you, IMMEDIATELY. No intermediate third parties taking your hard earned money.
6. Scale is irrelevant. Whether you publish two videos that sell once or twice, or a thousand that sell a million times each, it all works the same.
7. You can monetize content DIRECTLY in social media.

Sound impossible? Nah, just better tech - the system uses "Blockchain" technology, which is also a part of Bitcoin, a virtual currency which has over 10 million users as of this writing. Head on over to Alexandria, and check it out. Below is an example of one of my more recent artifacts.

 

"Skatin' With Dayton" - "Pump" Shot and edited by me.


10 Basic "Do's and Dont's" of Photo Editing

June 13, 2015  •  1 Comment

As some of you may know, I've spent a decent amount of time working in the Film and TV industry in Hollywood - as a Cinematographer, Editor, and as a Colorist. As a Colorist, I developed a skill set that transfers quite well to photography, and has served me incredibly well both in my professional work as a photographer and cinematographer, as well as in my personal artistic work.

Recently, I shot a set of photos for a client who owns some vacation rentals - I've done similar photos for her in the past, but this time, one of the final images in the set used so much editing, I thought a post on the subject was worthwhile, as it's something I haven't written about yet.



So, without further ado, here are 10 do's and don'ts of Photo Editing:

Do:

  1. Shoot with editing in mind - this means shoot RAW, and even if you can't plan every single part of your shot or your shoot, try to build habits that serve you well later in Lightroom.
  2. Underexpose for landscape, overexpose for portraits - highlights clip easily, skin looks muddy and sallow when underexposed. Exactly what the number is will vary depending on your equipment and your own personal style - experiment.
  3. Understand that even the best camera's dynamic range is limited, my A7R tops out at about 14ev.
  4. Give yourself room to crop! As you'll note, I didn't crop this image at all. This is a problem. I need to work on this. Many times I've been editing a photo, wishing dearly I could pull wider just a touch because I accidentally cropped out someone's toe, or ear, etc. You can't make it wider. You can only make it tighter.
  5. Shoot with as low an ISO as you realistically can; the lower the ISO, the more dynamic range you can eek out before noise becomes a serious problem. In the sample pic, you'll note that if I had been taking my sweet time instead of hustling through a shoot to get everything necessary in a tight timeframe, I'd have been able to shoot a longer exposure time, higher F-stop, and a lower ISO. When I'm in a hurry, I like to keep my exposure speed to at least 1/160th of a second to prevent vibration blur, etc.

Don't:

  1. Expect that what you see right out of the camera represents the true character of an image. Sometimes something amazing is hiding outside of what's currently visible.
  2. Underestimate the importance of editing your photos well. If I didn't edit my photos, I'd probably only have a dozen pictures on my entire site.
  3. Get too cute. It's one thing to see a photo and for it to be notable that it has been edited, it's another for it to be gaudy. (I realize of course that the sample image I've posted here is quite borderline gaudy) The difference is sometimes a fine line - and sometimes, an extreme edit is purposeful, intentional, and conveys a critical feeling that contributes to the photograph. Try to keep your editing tasteful, and always ask yourself if what you're adding contributes to the feeling the photograph is intended to evoke, or if it has no effect, or worse, a deleterious one. It's very easy to use Lightroom's tools to create things that look very artificial and unnatural, and while I (obviously) enjoy pushing the boundaries a little sometimes, I generally try and keep things in the range of the quasi-believable. Sometimes the key to this is a generous amount of feathering on your masks - sometimes it is a very high-resolution mask that has barely any feathering. Skies and soft shadows like feathering. Defined objects like faces and tree trunks like defined masks.
  4. Crush your blacks and clip your highlights. Look at the histogram, and attempt to maintain at least a small amount of detail in them while using the exposure slider to get the body of the image where you want it, and the contrast slider to push the boundaries until they just brush the edges. (obviously there are occasions where clipping is desirable, and in these extreme edit type situations, of course, go right ahead, I'm generalizing)
  5. Rush. Take your time. Have a cup of coffee, read the news, throw digital poo on Facebook, etc, and come back to things later. Sometimes I'll look at an edit later on and want to entirely re-do it. Using the "Virtual Copy" in Lightroom is very useful for doing this and not losing your previous edit.

 

Well, that's it for this post, hope you all enjoyed - feel free to hit me up with any questions or point out my mistakes (in a polite way please).


The Death of Paul Shephard

August 16, 2014  •  Leave a Comment

Well, I've been writing lately.  As a creative person and multidisciplinary artist, I never really know what strings inspiration will strike a chord with.  While the source of inspiration in this instance was simple aging, the result is something I am more pleased with than anything I've written in a long time, which is why I am publishing it here as a PDF for download for a limited time for free releasing it on the Amazon Kindle store for only 99 cents.


For all my fellow lovers of Science Fiction, for the crazy ones, for those of us who believe aging is mandatory but growing up is optional, this is for you.  Without further ado, here is "The Death of Paul Shephard" - I do hope you all enjoy it, especially the twist in the end.

What's the old man feeding the seagull have to do with the story?  Well, nothing, really.  ...but I think the story needed an image to go along with it, it was getting lost on social media without it.


Code Fluidics Kickstarter Campaign Launch!

October 25, 2013  •  Leave a Comment

A Kickstarter video I produced has just launched!  This is a seriously cool project run by a fantastic group of guys, so glad to see their campaign not only beginning, but off to a fantastic start!  Way to go, Code Fluidics!

From their Kickstarter page:

"Our first project takes color customization in products to a whole new level. We have developed a technology that allows anyone to change the color of their products in real time and as often as they want. Our patented technology uses microfluidics embedded into a product to control the color. There are virtually no limits to the combinations of colors one chooses, or how often one changes the color of a CODE-enabled product, such as the CODE Case."

If you get a chance, head on over to their Kickstarter campaign page and back them!

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