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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Quite Simply - Depth of Field

Someone posted this here, can't remember who though:

fov.jpg


So that's why you have to use smaller focal lengths, hence having more apparent DOF.
 
Is that to scale? Doesn't look like it, but would like to have that confirmed.

Can someone point to some actual FOOTAGE of a 16mm film cam or 2/3'' sensor going through its aperture range to show the real world look of the depth of field change? And I don't mean just "google up the HPX3000" or something, I mean some kind of controlled image test someone's done with a controlled environment and camera settings clearly labeled. The closest I've found was a 35mm adapter test on youtube but that didn't really help.

I've done my own little test with my Canon 30D where I shot at f2.8 and then closed it down to f5.6 (2.5 stop difference minus 0.5 since the Scarlet fixed lens will have a f2.4 aperture), but its still kind of hard to tell what it would look like with all the real world variables I was dealing with. Much thanx to anyone who has a link! =)
 
Looks like 16mm is a little too big on that picture.

Well, if you have a APS-C camera at your disposal you could frame something at let's say 40mm and shoot two images one at 2.8 and the other 5.6 and post them here... :).
 
Jamie Havill said:
DOF is all to do with the sensor size, focal length of your lens, and the aperture you are using.
Click to expand...

Correct. And in fact the relationship between sensor size and focal length+aperture greatly affects DOF. As the sensor surface area increases, the DOF at a given aperture with a given focal length lens decreases, which bodes well for larger sensors if shallow DOF is your thing.
Oh and the bad news. Larger sensors yield larger files and more perceived tonal scale, color gamut etc,but NOT necessarily a proportionate increase in sharpness.
 
M.Paul El-Darwish said:
Correct. And in fact the relationship between sensor size and focal length+aperture greatly affects DOF. As the sensor surface area increases, the DOF at a given aperture with a given focal length lens decreases, which bodes well for larger sensors if shallow DOF is your thing.
Oh and the bad news. Larger sensors yield larger files and more perceived tonal scale, color gamut etc,but NOT necessarily a proportionate increase in sharpness.
Click to expand...

Thanks for this. It is true, and the easiest way to put it. From what David has been quoted saying, and everything else we have learned we can come to this conclusion.

I'll quote David again here;

David Mullen ASC said:
Anyway, because you need to use shorter focal length lenses on smaller sensor cameras to get the typically desired fields of view, you can say that for practical purposes, smaller sensor cameras have deeper focus characteristics.
Click to expand...

David Mullen ASC said:
The 2/3" sensor gives you an effective increase in depth of field as if you stopped down a 35mm cine lens by 2.5-stops once you match field of view by using a shorter focal length compared to 35mm cine (divide the focal length you would use on a 35mm movie camera by 2.5 to get the equivalent focal length in 2/3" -- so instead of a 50mm lens, you'd use a 20mm lens, for example.)

So if you shot at f/2.0 on your 2/3" camera, it would look like you were shooting 35mm at a f/4.0-5.6 split. Whether or not that is acceptably shallow-focus is up to you, but in your typical close-up, the background would be soft at that stop.
Click to expand...
 
M.Paul El-Darwish said:
Correct. And in fact the relationship between sensor size and focal length+aperture greatly affects DOF. As the sensor surface area increases, the DOF at a given aperture with a given focal length lens decreases, which bodes well for larger sensors if shallow DOF is your thing.
Oh and the bad news. Larger sensors yield larger files and more perceived tonal scale, color gamut etc,but NOT necessarily a proportionate increase in sharpness.
Click to expand...

Without getting too pedantic about it, strictly speaking, DoF is not affected much by either sensor size or focal length - only distance to subject and aperture determine how much of the scene is in focus (and the definition of focus depends on the size and resolution of the screen/monitor/print the image is viewed on and its circle of confusion). What a lot of people mean when they say 'DoF' is actually bokeh appearance, which does depends on focal length: wider lenses=smaller BG behind subject=perceived sharper bokeh/BG; longer focal lengths=magnified BG with more apparent bokeh fuzziness.

Of course in the real-world to get the 'right' shallow DoF bokeh easily you need big sensors, long lenses and/or wide apertures.
 
Wikipedia:


The DOF is determined by the subject distance (that is, the distance to the plane that is perfectly in focus), the lens focal length, and the lens f-number (relative aperture). Except at close-up distances, DOF is approximately determined by the subject magnification and the lens f-number. For a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF; decreasing magnification increases DOF. For a given subject magnification, increasing the f-number (decreasing the aperture diameter) increases the DOF; decreasing f-number decreases DOF.


That means: at the same focal length on a 2/3 and a 35mm camera, I have to back up the 2/3 camera to get the same framing, thus increasing DOF.
 
Felix Knöchel said:
Wikipedia:


The DOF is determined by the subject distance (that is, the distance to the plane that is perfectly in focus), the lens focal length, and the lens f-number (relative aperture). Except at close-up distances, DOF is approximately determined by the subject magnification and the lens f-number. For a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF; decreasing magnification increases DOF. For a given subject magnification, increasing the f-number (decreasing the aperture diameter) increases the DOF; decreasing f-number decreases DOF.


That means: at the same focal length on a 2/3 and a 35mm camera, I have to back up the 2/3 camera to get the same framing, thus increasing DOF.
Click to expand...
100 % correct.

One of the ways that camera-persons cheat shallow DOF on wide(r) angle lenses is by staging a deliberately great distance between foreground and background. so the typical scenario is an subject at 3' from the camera [UCU framed shot] and one or more subjects at 10' or more from the foreground one. At full aperture or near it, you can pull focus and force quite a bit of bokeh between foreground and background, even though wider lenses inherently carry more DOF with them.

This has nothing to do with sensor sizes, just a heuristic of photo optics in general.

The wide-angle, pretending to have the shallow DOF of a tele trick is sometimes necessary if the set is tight and you can't back the camera and spread the actors too far apart.
 
Andy Taplin said:
Without getting too pedantic about it, strictly speaking, DoF is not affected much by either sensor size or focal length - only distance to subject and aperture determine how much of the scene is in focus (and the definition of focus depends on the size and resolution of the screen/monitor/print the image is viewed on and its circle of confusion). What a lot of people mean when they say 'DoF' is actually bokeh appearance, which does depends on focal length: wider lenses=smaller BG behind subject=perceived sharper bokeh/BG; longer focal lengths=magnified BG with more apparent bokeh fuzziness.

Of course in the real-world to get the 'right' shallow DoF bokeh easily you need big sensors, long lenses and/or wide apertures.
Click to expand...

This is based on that article floating around that has the picture of the toy trucks called sky something or other?

Well, it works mentally, but its technically wrong. He doesn't say that for his comparison shots he moved backwards, and that this is what caused that 'space distortion' for the given frame of view, not focal length.

Things in the distance appear flatter, and focal length simply magnifies this optically to give us a field of view our eyes could not achieve. Focal length does not distort space! And slap anyone who would tell you so.:nads:
 
Hey halsu, why don't you give an in depth explanation of focal length and depth of field.
Truth is, you're really good with that... (hv20.com)
 
Joseph Ward said:
I thought 50MM?
Click to expand...

A lot of still photographers who shoot on 35mm film consider a 50mm lens to provide a field of view approximating the focused areas from the human eyes of an average person. It's of course subjective, some claiming focal lengths as wide as 45mm. Me, I'm even crazier and think 35-40mm feels more like what I see, but that's just me. :crazy:
 
I think that "shitty" remark was because of the remarkable difference in size between the two sensor sizes (R1 and 2/3" Scarlet) in that pic. Sure it's smaller, but I'll take it over a three 1/3"-sensor cam (HVX200, etc) anyday.

HD-sensor-sizes.jpg

________
SELFMADE VAPORIZER
 
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