One of the most crucial elements for creating photoreal cg is lighting. To get accurate lighting from real-world environments, visual effects artists use 360 degree HDR images, taken on set during production.
The previous methods for capturing these HDR images were slow and cumbersome. They involved expensive specialty equipment like fisheye lenses, nodal pano heads and stitching software.
While the older techniques can achieve great results, they also require a variety of complicated tools from separate manufacturers all working in tandem with a high likelihood of error. They also require the VFX supervisor on-set to hold up the crew for 5–10 minutes for each shot. Unless it’s a big vfx show like Marvel or Star Wars, it’s a big ask to get time-strapped film crews to hold up their work long enough for each HDR to be taken, especially if there are many setups with CG.
There’s now a much more convenient way to get high quality HDR images on-set. It involves the use of Ricoh Theta cameras which are inexpensive, fast and easily available. Because they handle the capture of 360 images and stitching all on their own, the only other essential pieces of equipment you need are a tripod, a color chart and your phone.
When the Theta was released a few years ago, VFX trades touted its ability to take 360 images and use third party apps to do bracketed exposures, meaning it would take photos at different exposure values to be later combined into a single HDR. Since then, the native Theta app and firmware have been updated, eliminating the need to download a separate third-party app to do this. It’s now much more convenient and error-proof than before.
Below is my workflow for capturing 360 HDRs with the Theta. Keep in mind that you will need the Theta S or V models to do bracketed exposures.
Also, if you’re looking at which one to buy, you should know that the V model has a lower minimum ISO than the S (64 vs 100) and a faster maximum shutter speed (1/25,000 vs 1/6,400). This means that the V can capture about three more stops of dynamic range when shooting outside on a sunny day.
- Download and install the official Theta apps for your phone and computer
- Connect your Theta to your computer via USB and check for firmware updates (some cameras don’t have bracketed exposure ability out of the box).
- Disconnect the USB and enable wifi on the Theta (button below POWER button).
- Turn on wifi on your phone and app. Set the Wifi to the Theta signal.
- Wifi password is the serial number in the wifi name (numbers only) also located on the bottom of the camera.
- Click the Theta icon at the bottom of the map to get into Live View mode
- Hit the Gear icon to enter Settings and select “multi-exposure” from the drop-down menu. If you don’t see the “multi-exposure” option then your camera’s firmware is not up to date.
- In “multi-exposure” mode you will set all the values manually for each exposure. You don’t get the option to set your EV, but you can figure out the correct middle exposure and base your other exposures off of that. I have had success in adjusting the exposure for each shot by changing the shutter speed and leaving ISO the same.
- You can experiment with what works best for you, but in my experience FIVE exposures spaced 2EV apart seems to get the best results for HDRs on the Theta. This allows you to get exposures at -4, -2, 0, 2, 4.
- For daylight, set your white balance to 5600K. For tungsten (indoor) set it to 3200K.
- I generally set my ISO to 100 for daylight or 400 for indoors.
- You can’t set EV directly, but you can adjust it via shutter speed. For example, on a cloudy day, I have had success shooting five exposures at the following speeds: (1/25, 1/100, 1/400, 1/1600, 1/6400)
- By quadrupling the shutter speed for each subsequent exposure I am lowering the light level by two stops on each shot.
- Once you have all your exposure settings completed, hit the Shutter button at the bottom of the screen. You will see the progress on screen as each exposure is completed and the app will let you know when all five shots have finished.
- At this point you can go into the photos menu to verify that all the exposures completed correctly. Sometimes the phone may go into sleep mode while the app is running and stop communicating with the camera, so you need to check and make sure that the cycle has completed. I hold my finger down on the screen while the exposure cycle is in progress to make sure that my phone doesn’t go to sleep.
- You can download the photos directly to your phone, but I prefer to connect the Theta directly to my laptop and dump all the files from there.
- Connect the Theta via USB and dump the files into the appropriate folders. I like to make a separately numbered folder for each set of exposures to keep it all organized.
- In Photoshop go to FILE > AUTOMATE > MERGE TO HDR PRO.
- In the menu that comes up, click BROWSE, select all the files you want to combine into your HDR and hit OK.
- After a minute or so of processing, the HDR menu will pop up with the result. Make sure that the bit-depth setting on the right hand side of the screen is set to 32-bit.
- If there is a lot of movement in some of your exposures, you can select REMOVE GHOSTS to try and erase that from the HDR.
- Hit OK and now you can edit the HDR in Photoshop like any other file or just FILE > SAVE AS and save it as a .HDR format file (not .TIF or .PSD or .JPG).
- Bring the 360 HDR into your favorite 3D app and you’re ready to go!
So you may have noticed that HDRs taken with the Theta clip out when exposed directly to the sun. This is because the sun is so bright that even at its fastest shutter speed, the Theta’s lowest exposed shot will have clipped highlights. That clipping in the sun in your HDRs will affect your ability to get those hard shadows you will need for realistic lighting in your 3D app.
This issue affects many HDRs, but there is a simple workaround. I found another HDR with a better sun exposure, isolated it in Photoshop and now I paste it into my HDRs where the sun is located (set to Linear Dodge (Add) blending mode). Now, I get those perfect hard shadows in my renders.