BitMaestro
Well-known member
Yup, which is basically what's listed (in the pink-ish box) in the graphic:
GH1/2 AF100
(18.8x10.6) 16:9
CCF=1.18
Mark
GH1/2 AF100
(18.8x10.6) 16:9
CCF=1.18
Mark
Motion to have a chart created to finally explain the fov differences between sensors
PaPa
Major Contributor
This is magic. Saving this thread in my bookmarks.
G
G.P.
Guest
This is exactly what I was hoping this would do, one stop to answer a question
This is great, exactly what I was trying to come up with, it still might be a little off, but it does help a lot with the whole idea, plus a visual reference which is huge.
As far as dof goes, well it all goes tits up when trying to explain that in any way that doesn't get crazy numbers involved. I generally don't worry about dof because I am used to what lenses look like at a s35 size.
General rule of thumb for any lens is, the wider it is, the less shallow your dof. and the more "normal" or telly it is, the more shallow dof. You don't really need to calculate that, its pretty simple. So even if you're using a 10mm lens to get a 20mm fov, you pretty much know you're getting the dof of a 10mm lens.
Thanks for everyone who is taking their time out to calculate, as well as explain to the ones who don't exactly understand. Yes when you get into the math of things if you don't ALREADY know the math, its confusing. But once you learn the math, it will be something you can do in your head on any set for the rest of your life.
Remember not to get too caught up in it. After all, if you slap that lens on the camera, and you just aren't feeling it, all the math in the world wont save you. It comes down to what it looks like.... But this DOES help people understand which lenses to BUY. That way they know whats the best bang for their buck.
I agree with Barry about most cinematographers just know the 2 numbers, what a lens is like on a s16mm camera and on a s35mm. The new problem is, there are people getting into the dof and fov discussions that are completely new to the whole motion picture system all together. Most coming from just a 1/3' chip land, and the lens thing was never an issue for them. Even with Letus adapters and such, you had the ability to use either the FF35 or S35 crop just by zooming (and anything in between). So for them this information is gold.
I also hope its allowing conversations about lenses and other things to be had, without the same question popping up, you can now just direct them to this thread and let the conversations continue without interruption of dof/fov info.
I thought it might be helpful to repost here Glenn Przyborski's photo showing a strip of standard (not S35) 35mm motion picture film next to the GH1's sensor.
It's a good illustration of the GH1's so-called "cinema crop factor" (1.18x) compared to this popular 35mm motion picture film format. Cheers.
This is the most wonderful, happy-making, reassuring image I've seen on this forum. I love it.
Question, do the characteristics of DOF (not FOV) change with sensor size in both dimensions? There's no way I can think of wording this properly.
Like, take that photo. That ain't s35. s35 is wider, but same height. What does increasing size on x (not y/height) do? Does it change DOF? Crop is fully understood, I'm asking about would it get shallower?
Or do both x and y have be bigger? I don't even know if this question makes sense, but would a difference in DOF show between two sensors of same height, one being much wider than the other? Like 5D width, GH1 height. What does that do?
I just answered my own question. Correct me if I'm wrong, the problem here is trying to figure out exactly what happens when one tries to equalize focal length.
I'm on a 50 on a 5DII. I'm a meter away from my subject. I'm at let's say 2.8. I can see the whole picture. I got a 7D with the same piece of glass, same distance same f-stop same everything. All DOF characteristics hold, my field of focus is let's say 30 centimeters.
The only thing that is different in the image is how much of it I can see. The lens is projecting an image on a sensor. The sensor is smaller, the image is cropped.
Here's the change in DOF.
I back my 7D up until I get the same amount of picture showing up. I've seemingly got the same FOV. I can see as much of the walls as I can on that 5D. What changes? and Why?
DOF changes, very simply because the distance from my subject has changed. And if I'm not wrong, if I gotta focus on the backed up 7D on the same subject, my field of focus will go from that rough estimate of 30 centimeters to about 50 or 60, cause my distance from the subject has changed.
This is how I go about it. I don't like the idea of saying this lens is wide, this lens is tight, and generally having a list of 14-28mm = pretty wide 50mm = nice for portraits, this is taste related.
The question I need to ask in picking my lens, is how much do I need to see, and how much do I want in focus.
If I want to maintain the shallowness I'm getting on that 5D, I would check and see what a wider lens on the 7D could do if placed closer, just cause I know that closer focus means shallower depth of field.
It isn't necessarily backing the camera up, the distance from the subject is as governing a variable on how much I want in focus in accordance to my lens.
Which just tells me there is more than one way to make up for a crop, IF desired.
I want deep focus, with that full-frame 50mm FOV, I will back my crop sensor up, lengthen the distance to my subject, and be in deeper focus.
I want shallow, I'll put something wider on there, just so I can get close enough to use the closest focus possible, making up for DOF at the same time.
I prolly wouldn't do that if I had to get way too close that the subject distorts. Also I can see that perspective is rendered differently between focal lengths.
It seems a bit futile to shoot with the priority of matching a full frame. I'd much prefer using my eyes to judge how much I want to see, and using my calculator to figure out how much I get in focus depending on lens and f stop used.
Am I right? Is this correct? This is how I've been doing it, I've learned this very recently (like 6 months ago) and it hasn't been too tough to grasp.
DOF calculators really help there's one online that I'm trying to find that I like... cause you get the min focus distance and far focus distance. That's my governing variable in figuring out which lens to use.
DISCLAIMER: The 30 cm numbers and 60 cm numbers are non-educated guesses for examples only. I haven't shot full frame too much, and don't have a feel for how much 2.8 on a 5D 1 meter away would be in focus, I just said 30 cm to oppose the 60cm that happens when you back the 7D up with the same glass.
I'm on a 50 on a 5DII. I'm a meter away from my subject. I'm at let's say 2.8. I can see the whole picture. I got a 7D with the same piece of glass, same distance same f-stop same everything. All DOF characteristics hold, my field of focus is let's say 30 centimeters.
The only thing that is different in the image is how much of it I can see. The lens is projecting an image on a sensor. The sensor is smaller, the image is cropped.
Here's the change in DOF.
I back my 7D up until I get the same amount of picture showing up. I've seemingly got the same FOV. I can see as much of the walls as I can on that 5D. What changes? and Why?
DOF changes, very simply because the distance from my subject has changed. And if I'm not wrong, if I gotta focus on the backed up 7D on the same subject, my field of focus will go from that rough estimate of 30 centimeters to about 50 or 60, cause my distance from the subject has changed.
This is how I go about it. I don't like the idea of saying this lens is wide, this lens is tight, and generally having a list of 14-28mm = pretty wide 50mm = nice for portraits, this is taste related.
The question I need to ask in picking my lens, is how much do I need to see, and how much do I want in focus.
If I want to maintain the shallowness I'm getting on that 5D, I would check and see what a wider lens on the 7D could do if placed closer, just cause I know that closer focus means shallower depth of field.
It isn't necessarily backing the camera up, the distance from the subject is as governing a variable on how much I want in focus in accordance to my lens.
Which just tells me there is more than one way to make up for a crop, IF desired.
I want deep focus, with that full-frame 50mm FOV, I will back my crop sensor up, lengthen the distance to my subject, and be in deeper focus.
I want shallow, I'll put something wider on there, just so I can get close enough to use the closest focus possible, making up for DOF at the same time.
I prolly wouldn't do that if I had to get way too close that the subject distorts. Also I can see that perspective is rendered differently between focal lengths.
It seems a bit futile to shoot with the priority of matching a full frame. I'd much prefer using my eyes to judge how much I want to see, and using my calculator to figure out how much I get in focus depending on lens and f stop used.
Am I right? Is this correct? This is how I've been doing it, I've learned this very recently (like 6 months ago) and it hasn't been too tough to grasp.
DOF calculators really help there's one online that I'm trying to find that I like... cause you get the min focus distance and far focus distance. That's my governing variable in figuring out which lens to use.
DISCLAIMER: The 30 cm numbers and 60 cm numbers are non-educated guesses for examples only. I haven't shot full frame too much, and don't have a feel for how much 2.8 on a 5D 1 meter away would be in focus, I just said 30 cm to oppose the 60cm that happens when you back the 7D up with the same glass.
BitMaestro
Well-known member
Yes, DoF would change because it's related to/derived from the image diagonal (which obviously increases when you increase either width or height). But no, DoF would be deeper, not shallower, because, if nothing else changes, longer diagonals = deeper DoF.
A hypothetical sensor of those dimensions would have shallower DoF than the 5D (because the height is shorter, and therefor the diagonal is shorter) and it would be deeper than the GH1 (because the width is wider, and therefor the diagonal is longer). (This again assumes no other changes: same actual physical focal length (no adjustment for crop factor), same aperture, distance to subject, etc.)
Nope. DoF is already different at this stage because, at the same distance, the same focal length and f-stop will result in different DoF on sensors of different sizes. (Specifically in this case, DoF would be shallower on the 7D because, as noted above, when nothing else changes, the shorter diagonal of the 7D will result in shallower DoF.)
Well, that's sort of half correct. Essentially, everything would increase by a factor of 1.6--i.e. instead of 1m from your subject, you would move back to 1.6m; and instead of 30cm DoF, it would be ... 30x1.6=48cm; etc.
{Sidenote: actual DoF of a 50mm lens at f2.8 on a 5D at 1m would only be a few millimeters.}
That's obviously true. Instead of keeping focal length and aperture constant and moving the camera, as I noted up thread, you can also do the inverse: keep the camera in the same place and adjust both focal length and aperture.
Mark
Making more sense by the minute. The diagonal explains it.
Really? A few millimeters? I'm scared to check. Wow.
I totally understand the numbers, I jsut couldn't get them accurately in my head, but yeah it makes sense it is after all a multiplier, ...
The best way I can figure it out is to keep shooting consciously. Best way to learn, after all... just to balance out the discussions here, i suppose we owe it to the forum to actually go out and try this stuff...
Thanks Mark, and sorry to any readers I may have confused I was after all thinking out loud.
Tarek
Really? A few millimeters? I'm scared to check. Wow.
I totally understand the numbers, I jsut couldn't get them accurately in my head, but yeah it makes sense it is after all a multiplier, ...
The best way I can figure it out is to keep shooting consciously. Best way to learn, after all... just to balance out the discussions here, i suppose we owe it to the forum to actually go out and try this stuff...
Thanks Mark, and sorry to any readers I may have confused I was after all thinking out loud.
Tarek
Rick Burnett
Section Moderator
The DoF is related to the characteristic CoC (Circle of Confusion). Generally, from what i read, this has to do with the size of the pixel in the sensor, as it's typically defined digitally as the size of incoming light that would completely and only fill one pixel.
The best way I can think of describing this to people is this.
1) If you crop an image and blow it up inside your favorite graphics editor, it becomes blurry, which reminds you that you are increasing resolution over a smaller area. Going from 5D->7D
2) If you take a blurry picture and shrink the size down, it always becomes sharper, going from 7D->5D.
These are easy to test, and an easy way to remember what happens.
The problem is, when you change FoV on the 7D to get the same FoV as on the 7D, your DoF will be deeper at the same F-stop. I think that's why I've gotten confused before in the past knowing the above how the DoF is shallower at the exact same settings, which of course ends up being a much smaller FoV when you use the exact same lenses.
The best way I can think of describing this to people is this.
1) If you crop an image and blow it up inside your favorite graphics editor, it becomes blurry, which reminds you that you are increasing resolution over a smaller area. Going from 5D->7D
2) If you take a blurry picture and shrink the size down, it always becomes sharper, going from 7D->5D.
These are easy to test, and an easy way to remember what happens.
The problem is, when you change FoV on the 7D to get the same FoV as on the 7D, your DoF will be deeper at the same F-stop. I think that's why I've gotten confused before in the past knowing the above how the DoF is shallower at the exact same settings, which of course ends up being a much smaller FoV when you use the exact same lenses.
MichaelPaine
New member
http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm
More relevant for stills, but...
More relevant for stills, but...