Pole: Wide open (T1.x), how often

[Brian D. Goff]

I'm an open lens-to-the-max fanatic myself. T1.3/T1.4 makes my heart jump, but if I clear my emotions and step back a little, I must admit that it is simply a relict of my HDCam days and now in every day RED use, I simply don't open that wide unless absolutely necessary. Actually, I'll rater give my focus puller a T2+ and crank down the shutter to a 25/sec. Why, because wide open-dof is like only a few millimeters on some lenses and that's not to pretty. Just recently I was on a night shot - the DP said he needed fast lenses, but in the end nearly every single shot was stoped down to T2-3.

So here's the pole, how often do you really need so fast lens for the DoF. Since iso is going up and up in the next years, I think only DoF is the argument for a fast lens.

 

[hans de vries]

Well iso isn't going up the coming year for me, so I just bought a leica 35 mm f1.4, because there are situations where I don't have the time or space to set up a whole array of lamps; my f2 lenses were simply not good enough; but it's only partly a solution, because the dof is so shallow at f1.4 that it's really hard to focus when people start to move quickly; for which I would actually need to set up everything carefully again, and there was no time for that. In the end, there is no perfect solution for everything

 

[Nick Gardner]

Owning set of highspeed lenses, and a set of standard speeds, I often use the speeds stopped down, as opposed to the standards wide open. The only time I shoot wide open on speeds is in a doc situation where I have no choice. Focus becomes a major issue when trying to shoot moving subjects at a skinny stop.

Nick

 

[Andrew Wilding]

I love and whenever possible will only shoot on fast lenses - not because I ever really shoot them wide open though - I tend not to shoot below 2.8 if I dont have to - but because they tend to be sharper at t2.8 or t4 than a a lens with a 2.8 as its widest stop. In short, I dont ever like to shoot wide open - so the faster a lens, the more likely I can stop it down a little.

 

[Sanjin Jukic]

Normally you don't shoot wide open but you can shoot with it at some extreme low light situation of available light or similar...

At wide open DoF (Depth of Focus in this case) is always pretty short and tiny.

In the situation that you keep under control is possible to get a nice shots without getting out of focus.

Also a director can "coreograph" a movement of protagonists at short "DoF measured distance".

The most difficult is to shoot documentary style with handheld, some of stedicam and dolly during a sort of "follow protagonist" type of shots

when you must keep keep a camera constantly at the exactly same distance and movement speed from actor/actress and then you are fine with focus.

Also I did several wide open test handheld shots using a different high speed still lenses on RED1.

Below on these Vimeo links you can find the collection of handheld shots on R1 with a different high speed still lenses all at wide open:

- Leica 50mm-M Noctilux f/0.95 >>>

- Voigtländer Nokton 50mm f/1.1 in Leica M mount >>>

- Canon FD 50mm L f/1.2 test 1

- Canon FD 50mm L f/1.2 test 2

- Canon FD 50mm L f/1.2 test 3

 

[Stephen Williams]

At wide open DoF (Depth of Focus in this case) is always pretty short.

Hi,

I think you mean Depth of Field, depth of focus is related to collimation issues.

Stephen

 

[Sanjin Jukic]

Hi,

I think you mean Depth of Field, depth of focus is related to collimation issues.

Stephen

Stephen,

something explained like this below:

Depth of Field (Object Space)

The axial distance through which the object plane can be moved and still be in satisfactory focus is the depth-of-field.
For diffraction limited lenses, the depth of field can be calculated by dividing the wavelength of light by the N.A. squared.

Depth-of-Focus (Image Space)

The axial depth of space on both sides of the image within which the image appears "acceptably" sharp (as defined by the "allowable blur circle").
Depth-of-Focus = (M2)(Depth-of-Field)

Depth of Focus>>LINK>>>


"Depth of focus vs depth of field

While the phrase depth of focus was historically used, and is sometimes still used, to mean depth of field,
in modern times it is more often reserved for the image-side depth.

Depth of field is a measurement of depth of acceptable sharpness in the object space, or subject space.

Depth of focus, however, is a measurement of how much the film or sensor plane can be displaced
while an object remains in acceptably sharp focus. In this sense, it relates to a single plane in object space.

[1][2] It can also be viewed as the flip side of depth of field, occurring on the opposite side of the lens.

[2] With the first interpretation, the depth of focus is symmetrical about the image plane; with the latter,
the depth of focus is greater on the far side of the image plane, though in most cases the distances are approximately equal.
Where depth of field often can be measured in macroscopic units such as meters and feet, depth of focus is typically measured
in microscopic units such as fractions of a millimeter or thousandths of an inch.

The same factors that determine depth of field also determine depth of focus, but these factors can have different effects than
they have in depth of field. Both depth of field and depth of focus increase with smaller apertures. For distant subjects
(beyond macro range), depth of focus is relatively insensitive to focal length and subject distance, for a fixed f-number.

In the macro region, depth of focus increases with longer focal length or closer subject distance, while depth of field decreases."

LINK>>>

 

[Stephen Williams]

In the macro region, depth of focus increases with longer focal length or closer subject distance, while depth of field decreases."[/COLOR][/I]
QUOTE]

It's not only in the macro region, focused nearer than infinity the depth of focus will increase. Wide lenses have less depth of focus than long lenses, which is the reason you use a wide lens to set collimination.

 

[Sanjin Jukic]

In the macro region, depth of focus increases with longer focal length or closer subject distance, while depth of field decreases."[/COLOR][/I]
QUOTE]

It's not only in the macro region, focused nearer than infinity the depth of focus will increase. Wide lenses have less depth of focus than long lenses, which is the reason you use a wide lens to set collimination.

To conclude is to say that we are interesting in the Image Space that is actuallty Depth of Focus,

and the formula is:



Image Space>>>Depth-of-Focus = (M2)(Depth-of-Field)



So we have to measure Depth of Field and to place our shooting object between those two edge lines to get desired Depth of Focus.


That's a simple explanation of cinematographer's usual doing things in this situation.