Sensor format or crop in post?

Most camera now offer options that allow the use of different sensor sizes. So a full frame camera can be set to use a part of its sensor and hence produce an image that uses only part of the camera's potential resolution.

This gives the potential advantage of filling the frame with the subject, or potentially giving more reach with skittish subjects. (Increasing subject to camera distance.) Perhaps obviously, it does reduce the resolution of the image too.

However, (I think) you can achieve the same effect by cropping in in post? 

So for those that do use sensor size options that are smaller than native sensor size, I am wondering about its potential advantages?

Am I missing something here?

Adam

I shoot in raw and use post processing to get the shot framed to perfection. Once shot, you have what you have. No going back. Why limit your creativity? However, your choice!

Adam, I don't think you're missing anything. That feature is just an in-camera crop as far as I can tell, at least, that is how mine works. Maybe it's for people who need finished images or smaller file sizes SOOC?  

The bottom line for me is that you can find multiple and extensive threads on this site and others arguing the merits of APS-C over full frame and vise versa. My Sony camera is both with the advantage of high MP full frame and quality APS-C plus 1/400th & 1/500th( APS-C) sync speeds with the Sony A1, a bonus not found on another cameras. I very much like the high sync speeds for black water dives. I am sure the argument can be made that you could be using HSS flashes or that you can darken backgrounds in post just as you can argue the ability which I still have in both formats to crop in post. If you don't find any advantage to being able to do many of these things in-camera and would rather rely on post processing that should be your choice.

10 hours ago, adamhanlon said:

Most camera now offer options that allow the use of different sensor sizes. So a full frame camera can be set to use a part of its sensor and hence produce an image that uses only part of the camera's potential resolution.

This gives the potential advantage of filling the frame with the subject, or potentially giving more reach with skittish subjects. (Increasing subject to camera distance.) Perhaps obviously, it does reduce the resolution of the image too.

However, (I think) you can achieve the same effect by cropping in in post? 

So for those that do use sensor size options that are smaller than native sensor size, I am wondering about its potential advantages?

Am I missing something here?

Adam

There's no difference it is purely a crop - the only advantage might be to increase frame rates on some cameras or reduce storage requirements.  Psychologically it might help frame it better if the camera provides crop lines so you can maximise use of the smaller frame - it's rather easy to over estimate how many pixels you have when framing through the viewfinder.  

Regarding photography you are all perfectly right but today all cameras shoot video as well. And from the video point of view things are completely different.

Video has a 16:9 format and not 3:2 or 4:3 so even a full frame camera will never use the whole sensor.

Video has a fixed final resolution: 4K - UHD - 1080p. It can be almost impossible for the electronics of a camera to scale frames from 50 Mp to 12 Mp in real time without introducing defects or getting too hot. Ever heard of Rolling Shutter?

Mostly all cinema camera use Super 35 mm sensor size (aka APSC). It's true for all RED camera except RED Monstro.

Moreover all cinema camera have sensor resolution ( not size) near the final video resolution. A RED Komodo has a 19 Mp sensor. A GH5S has a sensor res. of 10 Mp.

Things are even more complicated than that and I think this article is a good starting point without going into the specifics of each model.

https://www.quora.com/Can-someone-confirm-or-deny-this-claim-When-shooting-video-using-a-camera-equipped-with-a-full-frame-image-sensor-the-camera-will-only-use-part-of-the-sensor-and-not-the-whole-sensor

Thank you @Davide DB We are all now completely confused

@Phil Rudin-I can see the point that you could shoot in APS-C and still crop in post, but surely you could do the same in full frame "mode" too? Are you not just giving away potential resolution by shooting in a cropped sensor mode? If so, where is the advantage?

Most full frame cameras offer the option of shooting in other sensor "modes." This is not by any means unique to Sony as far as I am aware?

I can see an argument (and partially support) that it is better to "get it right" in camera. However, for me at least, the creative process starts when I press the shutter, and ends when I export the file. If I need to crop in post to create the image I desire, I cannot see that this is any way less valid than changing the sensor mode on the camera from a creative standpoint? Both are simply different ways of achieving the same creative goal. Or am I (again) missing something here?

 Lastly, and this is off-topic (my apologies),  what is the advantage of faster flash sync speeds for blackwater? Unless I am (yet again) missing something, the only practical advantage it offers is reducing the potential effects of camera movement? I really like using HSS/faster flash sync in situations where there is too much ambient light, but can't see why it is useful at night in the black!

Adam

 

I understand that you are all photographers... I feel like a water drop in the desert... what I'm trying to explain is that while you could use that option for photos I guess it's mainly video related.
I had an A7S for a short time and it had the ability to work in APSC mode. I always thought this mode was for video because it allowed me to use APSC lens (I think it was the 10-18mm) and fill the entire 4K frame with the 10mm zoom. I could have worked FF and zoomed in to cover the sensor but for the reasons explained in my previous post, there would have been a big difference. At that time A7 and A7S had several limits in video. Also in a video editor it is very inconvenient to have to precisely trim frames.

Just my 2c.

@Davide DB or a rose among thorns
I guess that the ability to use APS-C lenses on a full frame camera would be an advantage for both still and video shooters?
Perhaps this is a good reason for using APS-C mode in general.

To counter this though, could you have used a 16mm lens to give the same coverage with the camera in full frame mode?

I also understand that "cropping" video is a significantly more difficult and time consuming process. 

1 minute ago, adamhanlon said:

counter this though, could you have used a 16mm lens to give the same coverage with the camera in full frame mode?

Yes but again the camera electronics has to resize FF frames on the fly and this process is highly power consuming.

I made some tests and on that old camera, video obtained with the APSC settings were far superior than FF video.

This was the main difference between A7S and R line. Nearly impossible to rescale a 50 Mp video frame without introducing some artifacts.

Latest camera are able to rescale them on the fly using powerful algorithms.

If you read camera specification you will discover that sadly many FF camera apply a default crop factor when shooting video. You bought a FF camera and you discover that on video it's nearly an APSC. 

13 minutes ago, adamhanlon said:

I guess that the ability to use APS-C lenses on a full frame camera would be an advantage for both still and video shooters?

I think that for the way modern camera are designed this is simply a free feature 

I think a key difference in cropping while shooting while cropping in post is about shooting what you see. If you use the APS-C feature on the camera, your EVF and the screen shows you what the cropped image would be like. You can make make the small adjustments to fill the frame, while staying further away from the subject due to focal length advantage.

So, the cropping process is same, but your workflow changes. Seeing the crop in camera allows for better composition, frame filling etc.

I didn't think about video, that makes perfect sense now!

I think having both FF and crop such as DX in one viewfinder helps see what the framing will be and it's quicker than trying to crop in post. But if you only need a small crop factor, like 20% then it's irrelevant. There's also the competition factor, where cropping may be limited to a certain percentage (say 25%), if you start at FF you may need to go beyond the limit while being in the DX/APSC mode (or whatever your camera calls it) won't violate that rule.

@David DB you're correct about many FF sensors cropping for video. Since the aspect ratio is different that is a necessity. But it is a frustration to find that video at 120 fps or 4x slow is shot on the equivalent of a cropped sensor - it of course varies with model and manufacturer.

The video on my newer Nikon bodies is way better than my old APSC/DX bodies though. So that's why I have switched to FF

Jon

Shooting in DX mode will produce smaller RAW files which in turn saves the disk space on your computer. Cropping the full frame image in post will still keep the full resolution RAW file on your HDD. So if you're sure you'll crop heavily in post and want to save some space, then just switch to DX.