Red One and ND filters

[Bill Goehring]

Does the DX range of Nikkors really cover the whole sensor, i had the impression the DX range is for the smaller Imagers ?
Manuel

A DX-sized image sensor (APS-C) is almost exactly the same size as the RED image sensor. In fact, DX lenses cover a little MORE than the RED sensor, so DX lenses will work fine.

The confusion comes from the fact that a 35mm still image frame is larger than a 35mm/S35mm cine image frame. Whereas the 35mm still image frame is sized so that the maximum width of a 35mm film strip matches the full height of the image frame, the 35mm/S35mm cine image frame is sized so that the maximum width of a 35mm film strip matches the full WIDTH of the image frame. This is because 35mm film travels through a still camera from side to side, and 35mm film travels through a cine camera up and down, among other reasons, I imagine.

 

[Simon Smith]

The use of a matte box can produce vignetting or (once again) am I wrong? LOL

I didn't know that a matte box could bring vignetting...

 

[Emanuel A.]

Don't you like a nice shallow DOF Emanuel?

To each purpose its own.

It's more a matter of its need with a wideangle bet.

http://www.fotoritim.com/yazi/lens-...-12-24mm-f4-g-af-s-ed-nikon-20mm-f2.8-mf-ai-s

 

[Bill Goehring]

Mr. Orange--

Sure, if the matte box is too narrow or placed too far forward with respect to the lens.

 

[Mark Crabtree]

Stopping down the lens

Stopping down the lens

Most lenses loose sharpness as the iris gets smaller and smaller. Maximum sharpness for most lenses is usually between 4 and 5.6. As you get to f11 many lenses get noticably softer and when you get to f32 the image can be practically unusable. So, it is more than just about depth of field. Do you need a matte box to shoot? No. You could use still camera lenses with smaller screw in ND filters. But the matte box helps assure better photos by minimizing glare and flare and allowing you to use grads to knock down hot skies. When I am shooting outside in the bright sun I try to shoot at f4 but vary the stop according to the depth of field effect I am going for. Rarely to I shoot anything over f8, just when extreme depth of field is required.

 

[Emanuel A.]

I didn't know that a matte box could bring vignetting...

Not necessarily. Maybe only when you have a non-removable/integrated wood like in that Nikkor AF-S 14-24mm f2.8. But I think that you already have your answers after Bill and khmuse explanations.

 

[Tim Lüdin]

He emanuel, the shalow dof thing is no hype at all.
That's the main reason I chose the RED cam because it gives me the same dof characteristics as 35mm Film. Otherwise I could stick with HDCams.
The whole filmlook talk is all about the shalow dof. This gives you the "filmlook" nothing else.

So if you like tack sharp images from the front to the end, then better stick with HD cams. They start almost from there.

Just my thoughts.

Cheers
Tim

 

[Bill Goehring]

In fact, this is why a lens hood that comes with a particular lens may perform BETTER than a matte box with a particular lens.

With zoom lenses, matching lens hoods will be sized so that they do not vignette at the wide end of the zoom range but will not perform optimally on the longer end of the range, ie. won't shade the lens as much as is possible at that focal length.

With a prime lenses, the matching lens hoods will be optimally matched for that focal length.

You can, however, adapt a matte box to perform optimally throughout the entire zoom range--so long as it does not vignette at the wide end--by sliding mattes into the front of the box that have openings just wide enough to avoid vignetting but narrow enough to provide optimal shading.

 

[Emanuel A.]

He emanuel, the shalow dof thing is no hype at all.
That's the main reason I chose the RED cam because it gives me the same dof characteristics as 35mm Film. Otherwise I could stick with HDCams.
The whole filmlook talk is all about the shalow dof. This gives you the "filmlook" nothing else.

So if you like tack sharp images from the front to the end, then better stick with HD cams. They start almost from there.

Just my thoughts.

Cheers
Tim

Sure Tim. To each his own. Mine is coming from after reading all these forums where I've seen a RED mania surrounding the 35mm shallow DOF gate. Applied to all focus length range, including the wide end. To me, a wider is a wider above all. More than the "hypest" shallow DOF. About "filmlook", I'm sorry but I'm afraid that's beyond any shallow DOF effect.

E.

 

[Bill Goehring]

I didn't know that a matte box could bring vignetting...

Just to clarify, vignetting can come from within the lens itself, ie. the glass elements within the lens do not fully cover the image circle required for the format being shot, OR vignetting can be caused by placing the lens inside a shading device that is too narrow for a particular focal length lens. Hope this helps.

 

[Caesar]

So if you like tack sharp images from the front to the end, then better stick with HD cams. They start almost from there.

Just my thoughts.

Cheers
Tim

I understand what Emanuel is saying.

I also believe that the use of this sensor will bring new frontiers in any way other than as only shallow DOF capabilities.

 

[David Mullen ASC]

You need ND filters. I'm amazed that so many people expend so much energy trying to find ways of avoiding getting ND filters. It's almost as as basic an equipment need as a tripod.

Even at 50 ASA, in direct sunlight on a clear day, the exposure is a little over f/16 (at 24 fps with a 1/48th shutter), which is nearly stopped-down on many lenses. Then you get excessively deep focus, you get softness from diffraction, and you get depth of field mismatching because you'll have shots made in the shade or in backlight or in overcast that will be more wide-open on the lens aperture. You don't want one shot at f/16 and then the next shot in the scene at f/2.8 - you generally want to work in a more limited range for visual consistency.

Plus rating the RED at 50 ASA will mean placing a lot of your brighter objects at or beyond the clipping point.

 

[Siva Kollipara]

I will state it again for emphasis. The gain of the camera is fixed. If you clip the sensor (or underexpose it) changing the ISO setting will have ZERO effect on the data acquired. The only things that changing the ISO setting has is to push or pull the processing of the .r3d file into a usable format. No matter what you do in post processing, if you clip the sensor, everything at or above that illumination value is lost and without detail.

I understood that the camera sentitivity is fixed at 320, how does it process late with different ASAs,This is onething that is taking sometime for me to sink into mind. can you explain me differently.
For example :
1)If I want to shoot my scene at 100ASA, should I lit for 100ASA or 320ASA.?
2)If I shoot/lit everyting at 320ASA, later can I change the exposure to 100ASA?

 

[Blair S. Paulsen]

What David said.

 

[Kevin Halverson]

I understood that the camera sentitivity is fixed at 320, how does it process late with different ASAs,This is onething that is taking sometime for me to sink into mind. can you explain me differently.
For example :
1)If I want to shoot my scene at 100ASA, should I lit for 100ASA or 320ASA.?
2)If I shoot/lit everyting at 320ASA, later can I change the exposure to 100ASA?

In every situation, you should "light" for the actual sensitivity that the camera is capturing and with the RED this never changes.

If you set the camera's 'ISO' to 100, then you risk clipping the image as the camera is actually rated at 'ISO' 320 (nearer 'ISO' 250 in my testing but that is only a .4 stop difference) regardless of where the camera is set. So if you don't ND down or change the aperture or change the effective shutter angle, you risk clipping a portion of the image.

Similarly, if you set the camera for 'ISO' 1000 and "light" a scene based upon an assumption that it is capturing at an equivalent sensitivity of 'ISO' 1000, then you will be underexposing the scene by 2 full stops because the camera is always operating at the native sensitivity. You can certainly use a higher 'ISO' when you process the images (RedAlert! or RedCine) but this is not changing the sensitivity of the camera, its changing the post processing only (pushing if you go higher, pulling if you go lower). The great thing about the RED is it has such a low noise floor that pushing a stop or stop and a half is perfectly fine as you will still get a reasonalby low noise image.

Again, where you set the 'ISO' has no effect on the image that the camera captures.

 

[David Mullen ASC]

To add to that...

If you decide you like the image characteristics of 100 ASA, then you'd light the scene for 100 ASA. Technically, since the sensor is really more like 320 ASA, you'd be overexposing somewhat. You can either color-correct the image in post back down to normal brightness, or process it as a 100 ASA image in RED Alert and it will do that same correction for you and then image will open up looking normal in brightness.

However, the clip point doesn't change despite different ASA settings, so basically you've lost a stop or two of overexposure detail by rating the camera at 100 ASA, at the gain of another stop or two of underexposure information.

In other words, the scene's brightness range is whatever it is, and you choose to capture an 11-ish stop section of that bigger range, and based on your ASA rating, you can decide whether to favor highlight or shadow detail end of the range. And lower ASA ratings will have less noise but more clipping, but high ASA ratings will have more noise but less clipping.

This is why simply rating the camera much slower to avoid using ND filters in sunlight outdoors is not a great solution, because that's the most likely scenario where you will be fighting to hold onto bright highlight information.

 

[Dalibor Fencl]

Yes that's it.
And after reading all that above I say myself why on the earth Red guys decided to call that ASA. It's so misleading...
So once again.
RED camera is 320 ASA. You can't change it. Period.
So are all DSLR cameras, even if you can play with ASA settings. You can't change the sensitivity of the sensor. You can only clip off either highlights or shadows.
In a normal sunny day, with given sensitivity 320 ASA you are at least at 11, but rather 16 or 32 F/stop. Those values are far less than optimal for any 16/35mm lens, to say it very gently.
Therefore is unavoidable to use ND filters. - there is no hype in it. It's just the way how it works.

 

[Daniel Reichenbach]

Time to reinvent Ansel Adams Zone system ;-) one of the easiest way for untrained redusers to understand dynamic range and how to deal with shadows and highlights arround this magic 320 ASA sensor. I googled for example this link: http://www.normankoren.com/zonesystem.html

 

[Joel Kaye]

And after reading all that above I say myself why on the earth Red guys decided to call that ASA. It's so misleading...
So once again.

I'm not sure the RED guys did really. It just came up as a way to relate the light sensitivity in some fashion.

David and Kmuse have done a great job of explaining this issue. We're going to have to evaluate each scene and figure out where we want the exposure to be.

 

[Mark Mannschreck]

If you set the camera's 'ISO' to 100, then you risk clipping the image as the camera is actually rated at 'ISO' 320 (nearer 'ISO' 250 in my testing but that is only a .4 stop difference) regardless of where the camera is set. So if you don't ND down or change the aperture or change the effective shutter angle, you risk clipping a portion of the image.

Very important! You can set the Red to ASA 100 which is dangerous because the built in zebras, false color, histograms, etc will CHANGE based on your camera rating... you'll be effectively clipping but zebras, false color, etc may look fine.