Saturday, February 25, 2012

Wireless tethering simplified (and cheap)

Elle
Why Tether?

In tricky lighting situations, or when you're experimenting with new lighting designs, it's great to be able to see previews of what you're shooting to get feedback on whether you've got good light coverage, see that the shadows are deep enough (or maybe too deep), and so on. But inspecting that teensy image on the camera's rear LCD screen is not very useful. The contrast is poor and it's just too darned small to see much detail. You can zoom in, but navigating is awkward and you lose the overall viewpoint.

What you'd like is to be able to take a shot and immediately view the results on a reasonable size screen, like a large desktop monitor, or a notebook display. That is, you'd like to tether.

Cameras meant for studio use, like medium format bodies with digital backs, are easy to tether as they have ethernet or FireWire interfaces for the purpose. You can shoot and your full-rez image is transferred right into Lightroom for viewing. That's fine for full-time pros with high-end budgets, but what about us part-timers? And while many semi-pro cameras (many Canon and Nikon bodies) can be wire-tethered using an inexpensive USB cable, my Pentax body (K20D) cannot.

So, am I stuck? No!

Wireless Tethering

My answer to the lack of wired tethering ability is to use an Eye-Fi wireless SDHC card and my PowerBook running Mac OS X. In order to make my solution portable, I could have bought an iPad and software (ShutterSnitch), but my old Apple PowerBook that was just lying around has a great screen, so I decided to use that as my preview device.

When I press the shutter, the RAW image stays on the SDHC card but a copy of the low-resolution JPEG is transferred via WiFi to the PowerBook where an Automator script sees it and sends it to the Preview app for immediate display.

End-to-end, my solution has these parts then:

Here's how you configure the bits and pieces.

Camera. Configure your camera to generate RAW and JPEG images. Configure JPEG images to be the lowest possible quality and pixel dimensions. On my K20D this means one-star for Quality and 2M for Recorded Pixels. This will speed-up the preview process and easily gives you a large enough image to see how you shot looks. I also configure my K20D to generate RAW images only by default and RAW+ (ie both RAW and JPEG) when I press the RAW button on the body. That way I'll only get previews when I specifically call for one.

Ad-hoc network. You need to be able to push preview images to the notebook as they are created, so this and the WiFi card need to be networked together. If you are working in your home or other controlled environment you can use the standard method of connecting to the local available network. But if you expect to be working in some random place, like a rented studio or outdoors, then you must connect via an "ad-hoc" network. This requires you to create an ad-hoc network on your notebook first, then configure the Eye-Fi card to see it. For a Windows or Mac OS X notebook, follow these directions.

Eye-Fi card. Having configured the notebook you should plug the Eye-Fi Pro card into the notebook and configure it to connect to your notebook's custom ad-hoc network. Follow these instructions on the Eye-Fi support site.

Eye-Fi Software. When the preview JPEGs arrive on the PowerBook I want to see them popup on the screen immediately for viewing. To accomplish this I arranged to have an Automator script, a "Folder-Action", connected to the image-drop folder. The Automator script wakes up when an image arrives and sends it to Preview.app. You configure the image-drop folder in Eye-Fi Card Settings. Open Eye-Fi Center, click on the little gear icon to the right of the Eye-Fi card under DEVICES. Then in the Photos tab, click Enable, and choose a folder under "Manage - Upload photos to:". Under Subfolder options select "Do not create date-based subfolders." Also disable uploading of RAW files in the RAW tab.

The drop-folder I use is /Users/{my-home}/Pictures/Eye-Fi but you can put them anywhere you have write permissions to.

Folder-Action. The exact way you create a Folder-Action and attach it to a folder varies depending on what version of Mac OS X you are running. My PowerBook is running 10.5.8 so I'll describe that ...

  1. Launch Automator.app
  2. Choose a Custom workflow
  3. under Library - Files & Folders double-click on Open Finder Items
  4. select Open with: Preview.app
  5. under File menu choose Save As Plug-in
  6. in the drop-down menu choose Plug-in For: Folder Actions
  7. select Attach to Folder: Other ... and select the image-drop folder you configured above.
  8. enter a name in the Save Plug-In As: field
  9. tick the Enable Folder Actions checkbox and click Save
Steve Harley has written up how to do this for newer Automators (10.7 Lion) and also in Applescript. (Thanks Steve!)

If you are running Linux, take a look at incrond to watch for the images landing in the drop-box folder.

If you are running Windows you're on your own at this point -- sorry! -- but I would guess that something similar to Automator.app is available in the OS or as a freeware or shareware application.

Test it out

Now the whole thing should work, so test it by installing the Eye-Fi card in your camera and take a shot. Make sure that you have JPEG creation enabled (RAW+). A few seconds after you press the shutter you should see the Eye-Fi Helper app's icon flash a small preview image and then you'll see the large sized preview popup in Preview.app.


References
  1. Jimmy Shoots Blog, "How To Wirelessly Tether Your Camera To Your iPad Using Eyefi and ShutterSnitch"
  2. Eye-Fi Pro X2
  3. Ad Hoc Network Setup Instructions
  4. Connect card to an Ad Hoc network
  5. folder action & Eye-Fi tethering workflow

Picture Credits

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