Aperture : Just Got My Camera!

[campbmic]

Hey guys! I am completely new to this site and new to photography and filmmaking in general. I purchased a Canon t2i and am having a blast learning about it. From what I've heard filmmaking has a lot of its foundation in photography concepts. So Ive decided to start learning as much as I can.

Today I tackled the concept of aperture and wanted to know if I got it right. From my understanding aperture (fstop) has a drastic impact on the field of view.

The lower the aperture the smaller the field of view, objects at various distances from the subject in focus will stay blurred.

The higher the aperture the longer the field of view, and more objects at various distances from the subject in focus will be clear and in focus as well.


Example-
We have three tomato cans at various distances down a table.

Aperture- 1.4f
ISO-100
Shutter Speed- 25



[URL=http://img97.imageshack.us/i/4211083.jpg/]

[URL=http://img828.imageshack.us/i/4211084.jpg/]



Aperture- 10f
ISO- 400
Shutter Speed- 4

[URL=http://img31.imageshack.us/i/4211085.jpg/]


I did notice that when you increase the aperture the picture gets darker, so I had to increase the ISO or slow down the shutter speed in order to compensate for this. Is this normal?

Im planning on taking a look at ISO and shutter speed next. Any tips? Or advice on what I should be looking at afterward?

 

[Cracker Funk]

Yep, you got it. Another thing that heavily influences depth of field is the focal length of your lens. Wider lens = wider depth of field.

Higher ISOs can produce graininess. Personally, I feel comfortable going as high as 1600, but I prefer to stay lower, and there are many people who do not recommend ever using anything higher than 800.

There's also the question of the T2i's native ISOs, but I have no clue what that's all about; maybe someone else can speak of it.

A group of us had a big-ol lengthy discussion about shutter speed, and the concensus we finally reached is that it's a good idea to use the 180-degree shutter rule (not to be confused with the other 180-rule) for no other reason than it is what audiences are accustomed to seeing (which is a good reason). The rule basically states that you should roughly double your frame-rate.

Additionally, depending on where you are, you may have lights to deal with that will look better with a particular frame-rate. Long-story short -- for 24FPS and 30FPS, shutter speed 60 is recommended (with 24FPS, doesn't perfectly follow 180-degree shutter rule, but close enough).

 

[chilipie]

Another thing that influences depth of field is the subject to camera distance - the closer you are focusing, the shallower it gets. This is very noticeable in your first three images.

This is just me being a pedant now, but strictly speaking aperture should be expressed as f/1.4, not 1.4f - it's a fraction with focal length divided by the diameter of the aperture.

 

[Theodebernacius]

There's much talk in this forum about the shallow DOF of film compared to digital. Suppose we have one film and one digital camera, we use exactly the same lens, aperture and distance to subject for both. Everything else being equal, will the DOF be the same?

 

[Cracker Funk]

There's much talk in this forum about the shallow DOF of film compared to digital. Suppose we have one film and one digital camera, we use exactly the same lens, aperture and distance to subject for both. Everything else being equal, will the DOF be the same?

Don't know, don't care. I'm sorry, I don't say that to be rude.

But there's so much talk about shallow depth of field because people are going way too crazy over it. It is a tool, one of many, that every filmmaker should have at their disposal -- that doesn't mean you should use it all the damn time.

To answer your question as best I can, I don't think it really matters -- with DSLR and a good lens you can get razor-thin depth of field if you want. Same is true for film.

 

[rayw]

But there's so much talk about shallow depth of field because people are going way too crazy over it. It is a tool, one of many, that every filmmaker should have at their disposal -- that doesn't mean you should use it all the damn time.

THANK YOU!

Buncha crazy people obsessing over some gimmicky capability.
Goodness. Gracious.

 

[Owen]

There's much talk in this forum about the shallow DOF of film compared to digital. Suppose we have one film and one digital camera, we use exactly the same lens, aperture and distance to subject for both. Everything else being equal, will the DOF be the same?

Good question. I don't know the answer though. I'm assumng with a 35mm sensor on a 5d the dof would be the same as a 35mm film camera. Can someone that knows what their talking about answer that please?
Dof is a big hype though. Shooting wide open say on a 35mm sensor with an 85mm will give you around 1cm or close too of sharp image. Pretty useless for most cases, when shooting a person you will get a sharp nose and blurry ears. Your better off shooting f/5.6 or f/8 for a which will give you more area in focus and also a nicer quality image.

 

[knightly]

Sensor size is the determining factor for the field of view in DSLRs that make them closer to 35mm film than most other digital in terms of DoF.

and yes Campbmic, the lower the F-Stop number, the larger the aperture, the shallower the DoF... the higher the number, the smaller the aperture, the longer the DoF.

 

[Cracker Funk]

Sensor size is the determining factor for the field of view in DSLRs that make them closer to 35mm film than most other digital in terms of DoF.

"Field of view" is a bit of a misnomer. It is not synonymous with "depth of field".

Sensor size does not have anything to do with depth of field, except that a cinematographer is forced to put their camera in different places, and use different lenses, to get the shot that they want. Camera-placement, lens focal-length and f-stop are what determine depth of field.

Sensor size only kinda-sorta influences depth of field in that a cinematographer will choose to put their camera in different places, and use different lenses, and different f-stops, depending on which camera they're using.

 

[Owen]

I forgot the sensor has nothing to do with Dof, thanks cf. So if a red and arri are sitting next to each other with the same lense and settings would the Dof be exactly the same? I guess the answer is who cares hey

 

[Cracker Funk]

I forgot the sensor has nothing to do with Dof, thanks cf. So if a red and arri are sitting next to each other with the same lense and settings would the Dof be exactly the same? I guess the answer is who cares hey

Okay, now that question I don't know the answer to. Cuz again, you're talking film vs. sensor. Not the same thing. I imagine there's probably a difference, but yeah -- who cares? The reason I say "who cares" is because you can acheive the same with either (if all you care about is depth of field).

 

[chilipie]

THANK YOU!

Buncha crazy people obsessing over some gimmicky capability.
Goodness. Gracious.

Extremely shallow depth of field is something that has become very overused in low-budget films recently, but to call a cinematic device that has been in use for decades a "gimmicky capability" is a bit of a stretch.

Cracker: sensor size does not have a direct influence on depth of field (the way focal length, f-stop and and subject distance do), but it does so indirectly through the choice of lenses you can use. You're right in saying that "field of view" is not synonymous with "depth of field", but a 1/3" chip simply isn't capable of producing shallow depth of field of what we might consider a "normal" lens (e.g. 50mm on a 5D). (Arri also produce digital cameras: the D-20/D-21 and the ALEXA.)

Owen: if the focal length, aperture and subject distance are exactly the same then the depth of field will be the same too. You could have a 1/3" camera with an 85mm f/1.2 lens and it would achieve just as shallow focus as a 5D, but you'd have such a tiny field of view it would be useless for all but the most telephoto shots.

Finally - I care! The maths and science of cinematography are just as important as the creative side when it comes to understanding why things are done a certain way… I might come into the screenwriting forum and say "who cares!" when someone asks for the millionth time about formatting

(Forgot to add - if you want to complicate things further, read up on the circle of confusion, which is another factor in why bigger sensors can produce shallower depth of field - didn't want to explain it to people who don't care )

 

[Cracker Funk]

Finally - I care! The maths and science of cinematography are just as important as the creative side when it comes to understanding why things are done a certain way… I might come into the screenwriting forum and say "who cares!" when someone asks for the millionth time about formatting

Hehe. Sorry, I didn't mean it like that. The question, as I read it, appeared to be a question of whether one or the other can do a better job of creating shallow depth of field. But, of course either (film or DSLR) can be used to acheive the same result.

Of course I can't speak for rayw, but when I read the "gimmicky" comment, I took it to be more of a comment about the vast over-use of shallow depth of field. There seems to be so many people out there who are doing it for no other reason than the fact that they can do it, not driven by any real purpose. That's gimmicky. The continued use of shallow depth of field, over many centuries, in many (most) great films -- that's a different thing altogether, and definitely not a "gimmick".

As for the sensor size/depth of field relationship, we're in 100% agreement, we only choose to emphasize different aspects of the same truth. There is no scientific relationship between sensor size and depth of field. It is purely creative. But that doesn't make the impact any less real. Working under different circumstances, a cinematographer will make different choices. Sensor size will influence the decisions being made regarding lens and camera placement, and those both affect depth of field.

P.S. I don't care about screenwriting formats one bit.

 

[Owen]

I hope your following and understanding all this campbmic

 

[rayw]

Of course I can't speak for rayw, but when I read the "gimmicky" comment, I took it to be more of a comment about the vast over-use of shallow depth of field. There seems to be so many people out there who are doing it for no other reason than the fact that they can do it, not driven by any real purpose. That's gimmicky. The continued use of shallow depth of field, over many centuries, in many (most) great films -- that's a different thing altogether, and definitely not a "gimmick".

Yep. You got my meaning 100%.

Extremely shallow depth of field is something that has become very overused in low-budget films recently, but to call a cinematic device that has been in use for decades a "gimmicky capability" is a bit of a stretch.

Acknowledging I'm a (semi-) nube myself, when I watch studio productions by household-name directors they are using shallow DOF to separate principal subjects from background environment.
Great.
Cool.
But they don't do it in every bloody scene.

When I watch well financed indie productions I see the same.
Great.
Cool.
Indie-Prod doesn't mean uneducated or inexperienced.
It's just... whatever reason people have.

There are plenty of well directed indie features with fantastic production standards (some unfortunately with terrible acting) that don't go ape feces crazy with DOF.

Now, when I watch nube indie-prod... OMG! Every scene has gotta be a two-inch DOF scene! All of them! With wrack focusing!
THAT's gimmicky.


Over at another message board about screen writing all the super-nubes obsess over getting the "perfect" screen writing software program, and all those with experience give them the "Aristotle's Pen" speech: Do you think you'd write like Aristotle if you had his pen? The magic ain't in the pen.

Likewise, over here I see super-nubes insisting they accumulate the "perfect" camcorder or DSLR for their cinematic look and you guys kinda tweak their education along the line of "Spielberg's Camera" speech: Do you think you'd film like Spielberg if you had his camera? The magic ain't in the camera.

So, now the super-nubes wield their two-inch DOF shots all about as if THAT will make their cr@p story attract Pegasus and unicorns rather than flies.


S-DOF is a single technique to use, but certainly not the only one.
It's the mentality or thought process I take issue with.

 

[Theodebernacius]

Thanks for the info. Maybe Indietalk should have a FAQ for this kind of technical question.

I think I get the main idea. If DSLR sensors had exactly the same size as the the 35mm frame, the DOF should be the same (at a given aperture, etc.). But since sensors are smaller, to obtain the same image you have to either move away from your subject or use a shorter focal length, both of which will increase the DOF.

I guess the next question would be: are smaller sensors much cheaper and have DSLR manufacturers any plans of matching the size of the 35mm frame in the future?

 

[Cracker Funk]

Thanks for the info. Maybe Indietalk should have a FAQ for this kind of technical question.

I think I get the main idea. If DSLR sensors had exactly the same size as the the 35mm frame, the DOF should be the same (at a given aperture, etc.). But since sensors are smaller, to obtain the same image you have to either move away from your subject or use a shorter focal length, both of which will increase the DOF.

I guess the next question would be: are smaller sensors cheaper and have DSLR manufacturers any plans of matching the size of the 35mm frame in the future?

You got it, exactly. You sum up, in one tidy sentence, what it took chilipie and myself a couple paragraphs to explain. Although, to nit-pick verbiage, just to be clear, I would always use "shallow" and "deep" to describe depth of field -- to say that you "increase" depth of field is vague.

And, yes, there is a camera that matches 35mm film. Any time you hear someone use the terms "full frame" vs "crop factor", this is exactly what they are talking about. The Canon 5D is full frame -- it's sensor is just as large as 35mm film. The other DSLRs that people are using -- the 7D, T2i, T3i, 60D, and GH2 -- all have crop factor, meaning their sensor is smaller than 35mm.

 

[chilipie]

Just to confuse matters further, it's worth pointing out that while the 5D has a full-frame sensor, a 35mm stills frame is much larger than a 35mm motion picture frame - crop sensor cameras like the 7D and 550D have sensors a closer size to 35mm motion picture film than the 5D.

 

[SinEater]

And, yes, there is a camera that matches 35mm film. Any time you hear someone use the terms "full frame" vs "crop factor", this is exactly what they are talking about. The Canon 5D is full frame -- it's sensor is just as large as 35mm film. The other DSLRs that people are using -- the 7D, T2i, T3i, 60D, and GH2 -- all have crop factor, meaning their sensor is smaller than 35mm.

Cinema films shot on 35mm don't use the entire frame. The Canon 5D sensor is larger than the frame used in Super35 and other film formats. Super35 is much closer to APS-C sensor than the full frame 5D. Here's a nifty tool that lets you compare various film/sensor sizes.

http://www.abelcine.com/fov/

Edit: Chilipie beat me to it. The link I posted is still pretty useful, though.

 

[chilipie]

Cinema films shot on 35mm don't use the entire frame. The Canon 5D sensor is larger than the frame used in Super35 and other film formats. Super35 is much closer to APS-C sensor than the full frame 5D. Here's a nifty tool that lets you compare various film/sensor sizes.

http://www.abelcine.com/fov/

Edit: Chilipie beat me to it. The link I posted is still pretty useful, though.

All that speed-typing practice paid off! The whole frame is used in movie cameras, it's just that the film travels vertically instead of horizontally - the long side of a frame in a movie camera is the short side of a frame in a stills camera.