Which Camera to Use with Photogrammetry and PhotoModeler
PhotoModeler accepts photographs from most cameras including digital still cameras, mobile phone cameras, video cameras, and film cameras. Each type of camera has its advantages and disadvantages, but they all have a place with PhotoModeler.
What Is The Best Camera For Photogrammetry?
When choosing a camera, you should consider your project requirements and your budget. The most common choice is a digital SLR camera. Point-and-shoot consumer digital cameras are common as well. In some fields, such as forensics and accident reconstruction, film may be the only choice because that is the evidence at hand. Even cameras on mobile phones can be used in many cases. PhotoModeler can also work with photos taken with unknown cameras, providing there is some known information about the scene.
Consumer Digital Cameras are a good match for PhotoModeler. A typical project might require 1 part in 2000 accuracy or less for 3D models. Consumer-grade digital cameras are convenient, affordable and produce good results. You can expect to pay anywhere from $200-$600 US for a new consumer digital camera. We recommend that if possible you use a camera with a fixed or prime (non-zoom) lens for photogrammetry - they are more stable and less issues are caused with calibration. A zoom camera can be used though - esp. if you use it at its wide angle setting always and it is stable at that zoom setting.
Digital SLRs are an even better choice, if they are within your budget. With an DSLR you have more control over settings, get to choose the best lens (usually a fixed, non-zoom, wide angle), and often have higher resolution. You can expect to pay anywhere from $800 to $8,000 for a good DSLR and lens.
Digital mirror-less cameras are good as well. They are a form of DSLR without the mirror and the bulk. They are smaller, sometimes cheaper, and with specs often matching DSLRs.
Cameras on Drones and UAS are lightweight so they can be carried aloft. Some cameras are built into the drone, some are sport cameras like the GoPro, some are small point and shoot, and some are full DSLRs. PhotoModeler can accept most drone camera imagery.
Video Cameras are also compatible with PhotoModeler. Analog video can be digitized with a frame buffer and used in PhotoModeler. Analog video cameras provide low resolution images and the resulting PhotoModeler projects are usually accurate to 1 part in 250 or less. HD digital video cameras are common – they improve on standard video with greater resolution, greater image stability frame-to-frame, and easier transfer to your PC (USB, firewire or SD Card). The resolution is not as high as a still camera.
Film Cameras can be used by PhotoModeler when the image (from negative, positive or print) is digitally scanned. A good quality scanner is needed. Film cameras are not commonly used as digital camera image quality is so high now. Film is used in PhotoModeler when that is all that is available such as in forensic cases.
What Is The Best Digital Camera?
There are so many digital cameras on the market, with new ones becoming available at such a rapid rate, that we cannot recommend a particular brand or model. The most important items to look for in a digital camera are:
Can I Use A Camera With A Zoom Lens?
We normally recommend fixed lenses with PhotoModeler (i.e., no zoom or 'prime') but zoom lenses can be used with PhotoModeler if extra care is taken. PhotoModeler needs to know the focal length of the lens for each picture taken. Some cameras do not store focal length information, so you will want to fix the zoom at a known focal length – such as the widest angle, the most telephoto or the power-on-default zoom – before you start shooting. Be careful not to change the zoom during the photo shoot or your accuracy will be affected. Some consumer cameras have a more stable zoom than others (i.e. the focal length does not change as you handle the camera) – these cameras are preferred.
Can I Use the Camera in My Mobile Phone?
In most cases, a mobile phone camera can be used by PhotoModeler. There are a few caveats: a) the resolution and image quality can be lower than many other digital cameras, b) some modern mobile phone cameras use OIS (optical image stabilization) which can reduce accuracy and increase project residuals, c) some mobile phone cameras will do manipulations such as auto-rotation, or auto-lens choice and merging, that can cause issues with photogrammetry, and d) it can be more difficult to get photos off a mobile phone than a normal camera. But what is great about a mobile phone camera is that most of us have one in our pocket!
What Is Camera Calibration?
Camera Calibration is the process of determining the internal values of a camera (called 'interior orientation' in photogrammetry). These values are focal length, format size, principle point, and lens distortion.
There are a few different ways to get the internal values for a camera:
- EXIF header data - digital cameras often write the basic values to the image headers. Sometimes this can be enough.
- Inverse Camera - often use in forensic cases where you know nothing about the photo. Requires control points.
- Independent Camera Calibration - PhotoModeler has a Calibration project type that allows accurate pre-calibration of a camera.
- Field Calibration - PhotoModeler can calibrate (or fine tune a pre-calibration) a camera when solving certain project types. Often this requires quite a strong geometry of camera positions in the project.
- Auto-Calibration - Auto-calibration is a variation of Field Calibration and is used in automated Coded Target and SmartMatch projects. The calibration is carried out without user intervention during processing.
Further information on calibration can be found in our Knowledge Base.