What does a fast lense mean?

J

Jamaine

Active member
Dear Forum users,

What is mean't when someone say they have a fast lens? Also can someone direct me to where I can a proper understanding of Lenses.

Thanks in advance.

Jamaine
 
A "Fast" lens means a lens with a wide aperture. Currently, lenses that have a f-stop of about f2.8 or lower, is considered a relatively fast lens. The smaller the f number the wider the aperture and the "Faster" the lens. I will see what links I can find on general lens information.
 
Its an old shutterbug term. Fast meaning 'this lens allows you to shoot with a fast shutter'
remember that back in the day you couldn't change iso, you were stuck with the asa of the roll in your camera.
In order to shoot fast shutter on your current film stock you needed a fast lens.
ie one that opens to a wider than usual aperture
 
A fast lens allows you to make one thing in focus and everything else blurry.
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im assuming this was supposed to be funny (which it is) but mostly true.

where a lot of new folks get tripped up is they get their shiny new HDSLR and a "fast prime" lens (prime meaning single focal length, not a zoom) then wonder why their subjects nose is razor sharp, but their ears are blurry.

one of the qualities (or drawbacks, depending on how you are planning your shot) of faster lenses is the lower the f-stop number (faster) of the lens, the shallower your depth of field (DOF) meaning there is a much shorter distance between whats in focus, to whats ot of focus.

another new user pitfal is that they think they want that shallow depth of field because theve been told that thats part of the "cinematic" look. but sadly, thats only one part of the puzzle. and a piece that gets WAY overused. especially in the "instant DP" world that the DSLR "revolution" has created
 
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I agree with wgzn 100%, thank you for saying that, I am so tired of all these DSLR movies that are like half in focus and half out of focus. No one seems to notice how freaking cheap that looks, it was okay at first but now way overused
 
You guys are all wrong, a fast lens means it has fast disconnect so that you can change lens fast. :-)))
 
Jamaine said:
Ok so how do you decide when & when not to go for that shallow look.
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I'll use my 'wedding coverage' experience here for situations that would involve photos of 'humans'... Until the Wife dragged me into her wedding business, I had mostly shot product, architectural, and scenic photography... then I had to get a real job outside of photography altogether...

So, for architecture and scenics I was of the 'deeper than deep focus', using features of 4x5 cameras to get the appearance of 'sharp focus' from close up to infinity.

For some product photography there was a requirement to throw the 'background into softness', so I would measure and stop down to give the product 'sharp focus', and the background elements 'soft'. But still not as soft as what some people do, as demonstrated here frequently in the clips people upload.

For the wedding business, most of our coverage was shot at F/8 or 'two stops down from wide open'. This is were most lenses have their best performance. Since we were shooting stills, we could use flash units to boost light as needed to maintain that F-stop.

For my motion picture activities, I've tended to f/5.6, so, I've not changed all that much, just compensating for having to fix the shutter speed at 1/50 or 1/60 depending, which is the usual shutterspeeds for shooting at 24 fps, or 30 fps, respectively.

The most significant reason why I would use 'shallow' depth of field is to separate subject from either foreground or background, when 'lighting' just could not be achieved to do the separation. For Weddings one is not always given ideal situations, and so, using a shallow DoF will throw background that is 'uninteresting', into 'fuzz' and hopefully out of the consciousness of the person viewing the image... At Wedding photography seminars some presenters like to show how a trash dumpster can be 'fuzzed' by correct DoF setting and eliminated from the image... no know really knows what that green blob is... and so, the wedding couple is the subject of the shot, and nothing else distracts... I tried to avoid taking shots of brides and grooms in front of trash dumpsters... but sometimes there was other clutter to eliminate.

The only time I would really shoot wide open is if I was shooting in 'near dark', and just needed to get a shot... Better to have fuzzy background than miss a "Decisive Moment", a term to indicate that 'a complete story can be told' from the image taken... News/Event photography is a series of 'decisive moments'...

In narrative film, shallow DoF is used to force the viewer's attention on the specific subject that the filmmaker wants to be the focus. So, in some cases one will have a 'rack' focus, where an actor or object is 'out of focus' but then quickly comes into focus, as the story develops. This is often used in a 'two shot' were focus is on one actor, then quickly changes to the second.

More static shots will have some object, or some actor whose facial expression is part of the emotional content of the scene, and a extreme closup is used to connect the viewer with that emotional content.

Of course some people use it as a 'cool device'... but that is really not it's purpose, as far as I'm concerned...
 
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