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is it ok to shoot at f1.4?


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#1 Scott Willis

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Posted 13 February 2008 - 05:14 PM

this actually stems from some investigation i'm doing to buy prime lens for my still photography setup (old nikon f3 slr).

anyways, in my process of comparing lens and such i read where someone said this about a 50mm f1.4 lens:

"The purpose of purchasing a fast lens, is to make the image brighter for easier focusing. As a matter of purpose, you would not use any lens wide open. Most lens perform best at approx two stops down from the maximum lens opening."

i thought the purpose of a good quality lens is that you COULD shot at 1.4 and still look good. i've read that most lens will deliver relatively the same image quality in the midrange (say f8) but that the quality of a glass is determined by it's performance at the extremities.

i know this comes from photography (especially the focusing bit), but the issue is still the same. a good quality lens that opens up to f1.4 is capable of actually shooting at f1.4 and looking good right?

in photography i've also heard mention of the 'sweet spot' of lens being around f8. but in cinematography i hear much more about controlling depth of field.
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#2 Alexander Disenhof

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Posted 13 February 2008 - 05:33 PM

As far as I know lenses do have a "sweet spot", and stopping down two stops allows for the lens to perform at its best. This said, if a lens is of high quality, than it should still perform reasonably well at T1.4. A while back I shot an entire short film wide open on superspeeds, and while there were some occasional focus issues, the picture quality itself looked fine.

If you need to shoot at 1.4, then shoot at 1.4, but if you can avoid it, than maybe try shooting at a higher stop.
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#3 Adam Frisch FSF

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Posted 13 February 2008 - 05:42 PM

That's pretty much true unless you're on Zeiss's new Master Primes. They're as sharp wide open as they are closed down, virtually.
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#4 Robert Houllahan

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Posted 13 February 2008 - 10:24 PM

i know this comes from photography (especially the focusing bit), but the issue is still the same. a good quality lens that opens up to f1.4 is capable of actually shooting at f1.4 and looking good right?



What are you shooting? If you have some 52/7219 (maybe with a push 1) and you are shooting outdoors in a city where everything in the shadows is metering a f0.7 (at best) and you want to retain detail of roadways, etc. working wide open will get you a nice picture with overall detail. If you are in a studio where you can light to a 5.6 why would you want to open to 1.4 unless you wanted a burnt neg? Maybe you do there are good reasons to have a look that you get from a burnt neg (3 or 4 stops over??) and maybe you don't have the budget to light to an 11 but a 4....


=Rob-
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#5 Michelob Fedusenko

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Posted 14 February 2008 - 01:05 AM

Unless you are blowing the image up to some large print, then the average joe should not be able to tell if the lens is not perfectly sharp wide open.

I would love to have a 1.4 lens so that I could shoot in dark areas. Many DP's/photographers prefer natural lighting. You don't have to open up that wide, but you can.

Also, it's not that wide so you can focus easier. A 1.4 will have a pretty shallow depth of field (depending on the focal length of the lens), so it will have to be a much more precise focus than say a 5.6.

It is perfectly fine to shoot at a 1.4. Do it! Learn, experiment. If you have the cash...
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#6 Satsuki Murashige

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Posted 14 February 2008 - 02:30 AM

Also, it's not that wide so you can focus easier. A 1.4 will have a pretty shallow depth of field (depending on the focal length of the lens), so it will have to be a much more precise focus than say a 5.6.

I think the original poster meant that focus would be easier to see for the operator, not that it'd make the 1st AC's job easier... It sounds like he's coming from a still photography background where you generally judge focus by eye through the viewfinder. On most SLRs, the iris will remain wide open to aid in focusing even with the aperture ring on the lens physically stopped down - the lens then stops down as the shutter is released. For a focus puller, T1.4 is a pretty brutal stop to work at especially in 35mm, but we'll do what we have to do to get the shot if the DP wants that look.

Most modern cine lenses like the Zeiss Master Primes (T1.3), Ultra 16's (T1.3), Digiprimes (T1.6), and Cooke S4s (T2) are just as sharp and contrasty wide open as they are stopped down. Older lenses like the Zeiss Superspeeds (T1.3) and Standards (T2.1) are noticeably softer and less contrasty wide open. Of course, some DPs prefer that softer look.
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#7 Michael Waite

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Posted 14 February 2008 - 04:04 AM

"The purpose of purchasing a fast lens, is to make the image brighter for easier focusing. As a matter of purpose, you would not use any lens wide open. Most lens perform best at approx two stops down from the maximum lens opening."

Sounds like that was written by one of those self appointed experts who terrorise camera clubs all over the world. Probably also insists that people follow the rule of thirds etc.
I have lenses for still & Super 8 cameras that open fairly wide (f/ 1.8, 2, 2.8 etc) & I love the results. These apertures are great for low light exposure & also for minimising depth of field.
Grrr .. I hate squares who lay down rules like that. Akin to the pixel peepers.

"As a matter of purpose, you would be led by your own creativity to try new things & assess the results with your own eyes."
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#8 Drew Hoffman

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Posted 09 March 2008 - 09:32 PM

Speaking in the world of still photography...

I shoot most of my stills on an old Nikon with a 50mm prime... I wish I could afford to get some newer and nicer lenses for it, but I keep having pesky things like rent getting in the way. It'll open up as wide as a "2.4" however, I don't shoot wide open unless I really need the light. For optimal sharpness, I need to be set to at least a 4... 5.6 is even better.

This is most apparent when the subject is 5' or closer and I have to blow up 8x10 or larger.

Keeping these things in mind, I can make choices and try to get the proper balance and highlight whether I need the extra lens speed... or I need the image to be razor sharp.

Although with modern film technology its not unusual for me to do something like push T-Max 400 (my personal favorite) to 600 or 800 without much problem. So, that'll buy me an extra stop and I can keep the stop down for better sharpness.

The last thing you can do is in printing, raising the contrast will increase the apparent sharpness of the image. Using multigrade paper, you can use like a 3 or 3 1/2 filter and fake some sharpness if that's what's most important.

The best thing to do is shoot a test roll using the lens and see what the sharpness looks like at 1.4... you may find it to be pretty sharp... or at least, you might decide the sharpness is acceptable to you.

Of course, using it with a motion picture camera is kind of a different story.
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#9 Dory Breaux DP

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Posted 09 March 2008 - 10:02 PM

Of the few lenses have used it seems that they all have a "sweet spot", although my DVX lens and then lens on my moms EOS20d (canon SLR) seem to perform pretty well when all the way open, but when there shut down all the way it looks like poo, especially my DVX (SD tho, what you expect?).
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