Jump to content

Confused about Frame Rate rules versus Light rules


Wit
 Share

Recommended Posts

I learned a lot lately about shooting with a DSLR  but one thing is still confusing me - the frame rate versus the light. Maybe this forum can help me (again) on this one?

 

A - As a new be on DSLR shooting I was recently thought that when choosing shutter speed I should use twice the frame rate I'm using. Especially when filming indoors with artificial lightning - avoiding the flickering effect. So when shooting at a frame rate of 24 fps I use 1/50 shutter speed and when shooting 50 fps I use 1/100 shutter speed.

 

B - But on the other hand there are the rules of light. The aperture, the shutter speed and the ISO settings which help you control your light. I red about the stops and how I can compensate them. And I red about the White Balance - all methods to adjust your lightning. 

 

 

My questions are:

 

1. - How in earth do these - A rules where I should double my frame rate to set the correct shutter speed work with the light rules - B? I won't have much space to adjust my shutter speed ...

 

2. - And what is the rule of thumb when setting your lightning - go from adjusting first your aperture, then to shutter speed and then ISO?

 

3. - And what if you want to freeze (speeding up the shutter speed) or blur your image (lowering shutter speed)? 

 

 

Or is there no rule of thumb?

 

It would be awesome if I could finally return to creating visual stories instead of learning all about the technics :P 

Link to comment
Share on other sites

EOSHD Pro Color 5 for Sony cameras EOSHD Z LOG for Nikon CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs

My approach is:

 

Set my aperture

Set my shutter (usually to 180deg, eg, if shooting at 24p, use 1/48th... but you can set this to however you think will look best for your shot)

Adjust my ISO and/or increase/decrease my lighting until i have good exposure

 

Thanxs!

What do you mean by 180deg?

What do you mean by increasing/decreasing light? Your Aperture? 

Link to comment
Share on other sites

Shutter speed to shutter angles at 24 fps the
math is (24 x 360) / Time Fraction
(i.e. 8640 / xx where xx is 1/ xx sec )
So the equivalent shutter angle for 1/50 sec
shutter speed is 8640 / 50 = 172.8 (i.e 172.8
degrees)
Sec Equivalent Degrees
1/32 =270
1/48 =180
1/50 =172.8
1/60 =144
1/96 =90
1/120 =72

 

Ok try shoot 1/50 most of the time if you can

that gives a cinematic look and reduced mains 50hz flicker on lights if your mains is 50hz like it is here in the UK

if your subject is moving fast increase your shutter speed to 1/100

Saving Private Ryan was shot by cinematographer Janusz Kamiński at 45 degrees which is about 1/160 sec

as he was shooting film stock he also used and out of phase shutter to get a jerky WW2 newsreel look at times.

We can't do this on DSLR but we can use the higher shutter speeds to capture fast movement. - you get less motion blur that way.

 

I have shot 2 pop videos in low light with fast lenses at 1/30 as it gave me more light as it was a dark set.

so different setting work for different lighting styles .

Link to comment
Share on other sites

Thanxs!

What do you mean by 180deg?

What do you mean by increasing/decreasing light? Your Aperture? 

 

Another way to think of shutter angle is the ratio of time the shutter is open to the time of the frame.

 

Think of the total window(time lapse) of each frame as being 360 degrees. Assume you are shooting at 24 fps, and each frame is exposed for 1/48, then your shutter angle is half of the total window(1/48 is one half of 1/24), or 180 degrees. 

 

In short, at normal fps(24-30), the higher the shutter angle, the more blurry the frames will be, and the smoother your action will look.

 

If you use a really low shutter angle (say you are shooting wide open, in bright sunlight), your frames will be crisp, but your action will might look jittery.

Link to comment
Share on other sites

Frame rate has no relation to exposure or light. Frame rate is how many individual pictures are being exposed/projected per second. Shutter speed is how long the shutter stays open, in seconds. The only thing you need to know about shutter angle is that it effects motion blur between frames.

B: The light 'trio' of aperture, shutter speed and ISO is really for digital stills. For video, only consider ISO and aperture for controlling your exposure. Since DSLR's don't have a global shutter and you can't control the shutter angle, the only way you can control that is by your shutter speed (hence the 'inverse of twice the frame rate'). White balance really doesn't have anything to do with exposure. To a degree it does, but it is the temperature of the color white. Higher numbers give you a warmer (yellow/orange) white, lower numbers cooler (blue) white.

 

2. It depends on the situation, but I usually set the aperture first then use the lowest ISO I can and still retain proper exposure. I shoot at 1/40 shutter speed, you get a little bit more motion blur, but it's barely noticeable compared to 1/50 (for 24fps. I shoot 1/125 for 60fps). Don't even think of shutter speed in terms of a way to adjust your exposure. Leave it at whatever it is for the given frame rate (1/40 or 1/50 for 24/25fps or 1/100 or 1/125 for 50/60fps) and don't change it; unless you intentionally want to manipulate the motion blur. See below.

 

3. If you make your shutter speed faster, you'll lose more motion blur between frames, and motion starts to look artificial/strange. But if that's what you're going for, do it. If you slow it down (the GH2 can only go down to 1/30, I think, in 24fps) then you'll have the opposite. You can get down to 1/2 second shutter speed in Manual Movie Mode with the GH2, but IMO, it's only good for time lapse stuff.

 

So really, there is no rule of thumb, aside from the 180 degree shutter concept for 'natural' motion blur. The challenge of shooting 1/40 or 1/50 shutter speed is that it is a rather slow shutter speed. In bright, outdoor situations, to retain shallow depth of field, you'll need to use an ND filter. You can get sets or a variable one. 

Link to comment
Share on other sites

What a helpful information thanxs all!  

Hahaha and yet again something added to the technical list (something I didn't hear about before)  - the shutter angle!

 

Yep I thought so need a ND for my GH3 kit lens. What would be a good and affordable ND filter for my 12-35 Panasonic lens? B&W and how many stops I need? I'm not sure if I ever buy a matte box - it makes the camera a lot bigger. But I probably will add some prime lenses to my camera in the future.

Link to comment
Share on other sites

ep I thought so need a ND for my GH3 kit lens. What would be a good and affordable ND filter for my 12-35 Panasonic lens? B&W and how many stops I need? I'm not sure if I ever buy a matte box - it makes the camera a lot bigger. But I probably will add some prime lenses to my camera in the future.

 

Go with the variable ND versus individual filters. Skip the matte box. Matte box isn't so much fun for run-n-gun. Check Dave Dugdale's site for a great vari-ND review video!

Link to comment
Share on other sites

Get a Cokin P series set with ND2, ND4 AND ND8

these are the best and do not degrade the image in any way

make sure you buy original Cokin as there are alot of cheap copies on ebay

I spent lot of time trying every ND made and for the money Cokin are best

I dont like Vari NDs at all as they do degrade the image and can add odd artifacts if you get light from side angles

you can get rainbow areas of color !

 

B+W is also a very good make (its made by Schneider in Germany) they are expensive

Link to comment
Share on other sites

Go with the variable ND versus individual filters. Skip the matte box. Matte box isn't so much fun for run-n-gun. Check Dave Dugdale's site for a great vari-ND review video!

 

You mean the fader ND this guy is talking about? Is there one of B&W too? Didn't find it yet - as I'm not sure what fader ND translates in my language and it's time to hit the sack now. ;-) Thanks a lot for all the help again guys!

 

https://vimeo.com/10433983

Link to comment
Share on other sites

Here's the link to Dave's video and some add'l info: http://nofilmschool.com/2012/12/dave-dugdale-variable-nd-filter-shootout/

 

The nice thing about vari-ND or fader-ND is that you can set your camera with your camera's specific baseline settings (ISO 200, 1/60 shutter). Then you can select the aperature you wish (f1.8) AND THEN use the ND filter to actually finish setting the exposure for your image. It makes shooting outside fun -- you get lots of free light to work with!

Link to comment
Share on other sites

Thanxs again - O yes maybe a stupid question but I like to get an answer - should you remove the UV filter when using a ND filter? Or can I stack them without loosing quality of image?

 

If I won't buy a vary-ND and I wanna start somewhere with one filter. For how many stops would I look for?

Link to comment
Share on other sites

Variable ND filters can be really handy, although they tend to remove a little bit of the sharpness of a video.

 

Here's a nice review of a few of the common ones: http://www.learningdslrvideo.com/variable-nd-filter-shootout/

 

 

I've personally used the Lightcraft Fader ND Mark II which I was pretty satisfied with - until I managed to have it cracked when it fell straight down on asphalt... I'm considering getting a second one of those :)

 

I also use the Cokin P-series filter system with square-shaped plexiglass ND filters which are also very useful - but not fully as portable (no loss of sharpness with these).

 

For proper exposure, I lock shutter speed at 1/50 for 24 fps video, set the aperture according to the style I want, and then try to keep ISO as low as possible. If it is very bright and ISO100 is not enough, that's when I use the ND's to get the proper exposure.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...