Camera setup for facade inspections?

[milkshakelake]

I need to do facade inspections for buildings that are 4-6 stories in height. I need to be able to zoom in to cracks and parapets. Anyone have a suggestion for what equipment to use? (I also posted this on a photography forum, but maybe someone here has faced this issue already.)

For reference, I currently use a Sony RX V (up to 70mm) on a tripod and it just isn't cutting it. It can't zoom far enough and the pictures come out blurry. I tried low ISO and narrow aperture - all the things that should give a clear image - but I think I'm hitting some hard limitations of the sensor and lens itself.

I'm currently thinking of getting a Sony A7 IV and telephoto lens. My only concern is the massive size and weight of the camera, lens, and tripod, along with other site visit equipment (measuring tools, drawings, paper/tablet, etc). Whoever uses it will have to lug it around all day, since they do multiple site visits in one shot. But then again, using a smaller kit will result in lower image quality, so I'm not sure about that either.

I'm not sure if this belongs on this forum; will move it if it doesn't.

 

[milkshakelake]

@Tomfh I grabbed the R7 today, thanks for the tips. I got 15-30mm and 800mm lenses. I tried them out at a store at the approximate trigonometric distance I'd actually use them (it's a pretty big store) and I was satisfied. Also grabbed some other stuff like an extra battery, SD card, and camera bag. The lens itself is ginormous, but I was expecting that. I'll see how it works in real life and report back to phamENG. I did try out some full frame stuff but as I expected, the lenses were just too massive for people to carry around on public transportation, though it did go to the required zoom with extenders.

@Hakon K Yes, I have a fancy tripod. I think it's a must when zooming that far. I wouldn't rely on the one-leg ones; need a lot of stability for the range I'm going for. The lens itself is also locked to f/11 so not a lot of light will enter it, meaning that it needs long shutter exposures.

 

[Tomfh]

Nice.

Get your head around the stabilisers. You have in body stabilizer, and lens stabiliser, which can give up to 7-8 stops of stabilisation, meaning handheld is generally fine for daylight shooting. You can be shooting your 800mm handheld at 1/125 or whatever, which at F11 is still giving you fairly low ISO shooting.

https://www.canon-europe.com/pro/stories/8-stops-image-stabilization/

The link you provided earlier is pretty good for judging how far you can take ISO:

https://www.dpreview.com/reviews/im...&x=0.31310511756569853&y=-0.45777232373093657

 

[milkshakelake]

I'm doing a bit of testing. The stabilizers are fantastic. I'm able to handhold shots, which blows my mind and everything I know about photography. But I need to use ISO 800 to expose it correctly with decent light, good grip (braced to the body), and breathing technique, which is basically ideal conditions. I wouldn't expect to always have that amount of daylight or employees to be able to achieve that. So it's tripods for now, and I'll do a bit of thinking about how to train employees to do it correctly. And maybe everything will work better on a day with even more sunlight.

Yeah, that link was instrumental in helping me choose a camera. People said a lot of good things about the latest rival cameras (Sony, Fuji) but based on that website, they just don't hold up as well as the R7. It also made me decide that I basically always need ISO 100 to 200 for all my shooting, though I'll try a few different things in practice and see how it goes.

 

[Tomfh]

What's the slowest shutter speed you're managing to hand hold the 800mm?

 

[wrantler]

This is prob controversial here but I do not think one can do an inspection with a zoom camera. Yes I can do a general inspection with one but if there is a crack I need to be up close to evaluate it. I use rope access to get up close and personal. If the client doesn't want to pay for it I walk.

 

[WesternJeb]

This might be a difference in an assessment and an inspection, in legal terms. I agree with Wrantler than an inspection might need a more thorough look through. An assessment/observation is definitely more surface level investigation. It depends on how it is being advertised I guess.

 

[milkshakelake]

@Tomfh I'll do some more testing and report back

@wrantler & WesternJeb For the real facade inspections, I'd do a representative sample of close up inspections (something like 25% of the building facade as RenHen pointed out) and do the rest with zoom. It's written into the local code (though they didn't specify 25% exactly), so it should be okay. The rest of the stuff is for preconstruction surveys, which is documenting the condition of adjacent buildings before construction, for which zoom is always acceptable for the types of jobs I do.

 

[Tomfh]

Close up inspection and telephoto camera inspection both have their place. I’d find it extremely limiting only being able to inspect directly. Cameras can inspect large areas quickly, can screen out non-issues, and can spot subtle things that warrant further direct inspection that would have been missed with the naked eye.

 

[capt_cryptic]

A good rule of thumb for the minimum combination of camera resolution, distance from facade, and width of facade captured by each photo is 0.05 inches per pixel. This is roughly equivalent to an inspector with good vision standing ten feet from the facade and using their eyes. You won't pick out hairline cracks, but you will see many common facade failures.

Here is how I calculate this for my own equipment:

Sony A7ii, 24MP, 4000x6000 resolution images.
6000 pixels * 0.05 in/pix = 300 inches = maximum 25 foot width of facade that can be captured horizontally in one image... assuming no loss of resolution from lens aberrations, which there are always some. Decrease this value depending on how small the defects you are looking for may be.

To determine how close I should be with a given lens to capture 25 ft width:

object distance = (focal length * object size) / object size in image

For a full-frame sensor which is 36mm wide (0.12 feet):

object distance = ([focal length in mm] / 305 mm/ft * 25 ft ) / 0.12 ft

For my collection of prime lenses:

Focal Length --- Distance
24mm --- 16 ft
36mm --- 25 ft
50mm --- 34 ft
90mm --- 61 ft
135mm --- 92 ft
200mm --- 137 ft
300mm --- 205 ft

In general terms, this formula is:
d = f * r * i / (12 * s)

where
d = distance from facade in feet
f = focal length of lens in mm
r = horizontal image resolution in pixels
i = facade documentation criteria in inches / pixel
s = horizontal sensor size in mm

I'll typically shoot a facade closer than this, but it's a good starting reference point. I also like to take hundreds of images with about 50% overlap then stitch them into one large gigapixel using Microsoft Image Composite Editor.

 

[milkshakelake]

I've dialed it down and figured things out for my specific needs, in case phamENG is interested. The optimal way that covers all use cases, and is transportable by an employee in car or on public transit, is this:
-Canon EOS R7 with 15-30mm lens + flash (for interior and exterior) and 800mm (exterior only)
-Exterior shooting with 800mm lens: ISO 200, shutter speed 1/125 seconds, 2 second timer, use a tripod
-For carrying on an exterior shooting day: a ~$300 photography backpack with wheels and handle (like airplane luggage), gives flexibility for either rolling it around or going up/down stairs, has tripod holder
-For carrying on a normal day: smaller super lightweight photography backpack for just the camera, lens, flash, and notepad/tools
-Camera is set with three presets: exterior handheld shooting (ISO 200, auto other stuff), interior shooting (ISO 1600, 1/125, auto aperture), and exterior shooting with tripod
-Tripod: aluminum with 360 ball head; I might replace it with a carbon fiber one to make it lighter

I understand that this setup won't fit most engineers' needs. I specifically need to zoom in like crazy and focus on small cracks. This setup works well for that. The 15-30mm lens is pretty standard and should be okay to buy "sight unseen," but I recommend trying the 800mm lens at a store to get a feel for how massive and zoomed in it is. It's for a very specialized use case, and one should experience if all that zoom is necessary. It also takes a while to train people on how to use it.


@capt_cryptic Thanks for the formula! Looks pretty useful. I guess in my case, I need something more zoomed than an inspector standing 10' away.

 

[phamENG]

in case phamENG is interested

Absolutely. I'm not quite the 'shutter bug' you and some of the other folks on here are...but I do enjoy photography and want to step up my game for assessment documentation. So thank you.

 

[milkshakelake]

I'm definitely not a shutter bug; figuring this out took a lot of time and was painful. I'd rather be in front of an Excel sheet or something. But here's to learning about new stuff and improving our work!

 

[jerseyshore]

Coincidentally I just got a request to perform some facade inspections in Jersey City today. I've evaluated facades before but never for this official inspection process. I didn't really want to do these and after reading this thread it's pretty clear me standing on the sidewalk with my cell phone isn't going to cut it.

 

[JMASE]

I have found laser scanning to be very helpful, and can provide out of plumb data, which can tell the story about bulging and rust jacking. I've had the laser scan guy also overlay visual photography on the same scan location for reference.