Question about converting real photo focal length to Studio camera
SnowSultan
Posts: 3,595
in The Commons
I'm trying to roughly match up a scene in DAZ Studio to a photograph, that according to its EXIF file, was taken with a focal length of 5.70 mm. However, when I set Studio's camera to 5.70 mm, it becomes extremely zoomed out with massive foreshortening; completely different from the photo. Do the values need to be converted or multiplied in any particular way to achieve a similar look? Thanks in advance.
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5.7mm will be an incredibly wide angle, so your results sound appropriate. It's also incredibly odd to have a non-integer focal lengths on physical lenses. I'm not sure how to account for the difference between your DS and the metadata.
Hm, so Studio's interpretation sounds correct. I didn't take the photo, so I don't know why it's listing the focal length at 5.7mm. Have you ever been able to accurately match a Studio camera to proper photo metadata? If so, I'll just assume something is screwed up with this photo's information.
The only times I've tried to replicate photos (actually still frames from movies) I didn't have camera metadata on hand, so I can't tell you from experience. Are you sure it doesn't say 5.7Cm? That would mean 57mm, which is still a little unusual for a focal length but more appropriate for a portrait (if that's what you're doing).
To make the correct calculations you also need to take into account the sensor size of the camera. You can't compare a phone camera's focal length with a DLSR.
https://www.thephotovideoguy.ca/blog/sensor-sizes-and-focal-lengths
5.7mm focal length sounds like it was taken with an iphone, with the crop factor try changing it to 26 or 28mm focal length and see if that does it.
Are you sure the data in EXIF is 5.7mm not 57mm ? From which software you saw it and camera model ?
Edit: I totally forgot about the lens from a phone, ho~ Richard's formula turns out to be useful !
There are issues with modern camera focal lengths. The lens to focus point distance is a real world physical distance. What that actually looks like in the image is something else entirely.
For instance with a 35mm film camera, a 50mm focal length gives a picture similar to how the human eye percieves things. That is with a focal length/sensor size ratio of 50/35 or 1.43. Anything under 1.43 is wide angle, anything over is telescopic. If you use a 50mm focal length lens in an 8" x 10" plate camera (film diagonal of 320mm) and you get a very wide angle shot - focal length ratio of 50/320 = 0.156. However, if you only take a 35mm diagonal segment of that 8x10 plate, you will end up with exactly the same image as seen on the 35mm film camera with a 50mm lens. It's all down to the focal length to sensor size ratio.
That's also why phone cameras with 5.7mm focal lengths can provide images that can look like 35mm film images, or immensely wide angle lenses. You need the additional piece of information, the sensor size for the image you are looking at. Then you can convert it to DS/35mm Film camera equivalent focal length using the following formula:
DS focal length = (Camera Focal Length x 35)/(camera sensor diagonal)
Regards,
Richard
Thank you for the information so far. Here is the EXIF information from the photo. It is apparently 5.70mm and was taken with an actual camera (not a phone). I don't see camera sensor information, but maybe it's called something else here and I'm not recognizing it.
Olympus C5060WZ
4× zoom range, 5.7-22.9 mm, equivalent to a 27-110 mm lens on a 35 mm camera
4× zoom range, 5.7-22.9 mm, equivalent to a 27-110 mm lens on a 35 mm camera
Very interesting, I tried setting DAZ's camera to 27mm and it came much closer to matching the photo. How did you do the conversion from 5.7-22.9 to 27-110mm?
Just looked up the specs on the Olympus C5060WZ. and saw this review...
https://www.wrotniak.net/photo/c/c5060-rev.html
The sensor on that camera was tiny 5.4×7.2 mm.
It's a 21 year old camera.
Ah, thank you. I guess that seems to be one semi-reliable way to do what I'm trying to do: get the EXIF info of the photo, look up details on the camera used, check for any focal length conversion data to a 35mm camera, and try dialing in that range to DAZ Studio's camera.
I've never taken a photography class, so there are camera terms I'd never understood before using Daz. But I've used DSLR cameras since they became a thing, just sloppily. Daz has taught me how to be smarter when buying lenses for specific needs and what all those functions are. Still have no idea what an f-stop actually IS, but I know how the length effects things now. :)
Each f-stop either doubles or halves the amount of light that a sensor receives... it does that by increasing or decreasing the size of a hole (known as a aperture) located in the lens.
This also effects the DOF (depth of field) which is how quickly the sharpness falls away in front of and behind the focal point.
There are others "stops" to consider... mainly shutter speed (each stop either doubles or halves the amount of time the shutter remains open).
And (increasingly more relevant) ISO, which is how sensitive the sensor is to light.
The relationship between these various stops of light determines the exposure.
That's an extra detail on top of a brief talk I had with a photographer while I was visiting a national park. I'd asked him about his massive cannon of a lens, because they're incredibly expensive and so I'd want to know before I buy, and his feedback was "It's not that it has a higher zoom power or anything like that. It's that the f-stop can be controlled more, so I can zoom in and slice it thin like a macro lens." That got me to playing with it in Daz to see what he was talking about, and it made me way more conscious of that as a feature.
ISO I'd discovered in a google search. When I got my first telephoto lens, I was stoked to take a moon shot, but all I got was white, overexposed blob. Knocking it down to 250 from its standard allowed me to count craters, I loved it.
Daz has also made me very conscious of angle, location and distance, and I've even started looking more at cinematography videos to talk about why certain movie shots work better than others (such as behind and object for a voyeuristic look), and it's fascinating stuff. It makes me wish this had been around when I was in my teens instead of so much later in life, I would have gone a completely different direction with my creative pursuits - and not in 3D.
I had a beautiful 5.7mm PL mount lens a few years ago, the same one Wong Kar-Wai used in Fallen Angels. It's a super wide angle but doesn't distort like a fisheye. I tried recreating it in Daz awhile ago and couldn't get it to look right either.
3D Universe has a product in the store named fSpy Project Importer for Daz Studio (https://www.daz3d.com/fspy-project-importer-for-daz-studio) that may be of interest to you. I bout it at the end of 2022 but have only explored it a little. fSpy Project Importer for Daz Studio is currently on sale.