How to choose a camera for photogrammetry?

Question

I'm interested in pretty serious non-aerial photogrammetry of interior and exterior architecture, but I've exhausted my available tools, and need to look into buying something suited to the purpose. Unfortunately, I'm pretty unfamiliar with photography hardware, and the landscape is... daunting, to say the least.

The single highest priority is image clarity. The processing phase of photogrammetry typically does not handle noise very well at all. Similarly, the more precisely defined the details are, the more accurately the software will be able to match and locate features. I've heard that there are cameras that will do image stacking in camera by moving the sensor while taking a burst of images, and then averaging those images together to give a clearer result. Manual image stacking in Hugin or Photoshop gives excellent results with a burst of hand-held images, but I don't know what this in-camera feature is called, to look into it. Obviously, a low ISO and manual shutter control are important, too. What contributes to image clarity/precision, and how much can I expect that to vary from camera to camera? Is there a good quantified measure for this that I can compare?

The second priority is image size. The more detail I can get in one image, the better. As I understand, though, high-MP cameras often compromise quality with aggressive noise filters, which isn't ideal. I'd like to shoot in raw, but it's not a big deal, so long as the image is good. What do I need to look for to determine if a camera is applying some kind of filter, and are there any noise reduction techniques that are actually good?

Thirdly, I need to scale gradually. I can't afford to go all-in just yet. I have to prove the process first. I'm looking to spend $300-$500 now, and $1500-$2000 later. Which of these features and what kind of quality can I expect to see in each of these ranges?

NON-priorities are interchangeable lenses and zoom. The lens geometry has to be identical for every shot of a given subject, in order for the software to make the assumptions it needs to make. Consequently, I might later decide to have different lenses for different subjects, but that's not a priority at the moment. And zooming will almost never be an option. One common application of photogrammetry is generating topography from aerial photographs, but I'll be doing all my shooting on the ground with a monopod or tripod.

I've been told that staying as close to 50mm as possible is good, but I'm not sure why. That might just be a good balance between depth of field and field of view. How should I choose a focal length?

So, what kinds of things do I need to focus on to meet these goals? What are the contributors to clarity, and are these things that I could expect from a nice point-and-shoot, or do I need to be looking at high-end SLRs?

Answer 1

As noise is a special issue for you I will address that point.

In general the larger the sensor, the less noise.

In terms of value for money that means you should look at used DSLRs or Compact System Cameras, anything from the last four or five years, using an APS-C sized sensor.

As a general technique you can minimize the effect of noise in a shot by taking an exposure on a tripod and allowing the exposure take as long as needed to use base ISO ( typically ISO 100 or 200, depending on the camera ).

If noise reduction concerns you, then shoot RAW and you should be able to "develop" the RAW in software with whatever amount of noise reduction you want, including none.

Stacking images with a modern large sensor camera shooting at low ISO probably isn't required, but in case even the extremely low level of noise in those shots bothers you, you can of course stack.

The lens geometry has to be identical for every shot of a given subject, in order for the software to make the assumptions it needs to make.

You should note that all lenses have some distortion, and eliminating this can be partly ( largely ) achieved during conversion from RAW to JPEG. Your processed shots with be consistent even after this processing.

The focal length choice is tricky as it depends on how wide an angle you want to shoot. The typical standard zoom on APS-C systems is an 18-55mm, which covers a good range for normal use. For your purposes you might consider other lenses, like a low distortion single focal length lens, but I would recommend that you get the so-called "kit" lens anyway, as you might use the camera for normal shooting anyway.

As you are very particular about optics I would avoid the compact system cameras, as they often rely more on software or firmware correction of optics than DSLR lenses. So a used DSLR would be the direction I'd suggest.