Thursday, 20 February 2014

Who needs a Noctilux when you've got VR?

If you feel like taking nocturnal landscapes using available light, you can buy a Leitz Noctilux ASPH ($11,000, 37,500 złotys). This lens has an aperture of f0.95 (wider than f1 - the aperture is wider than the focal length). A mighty piece of glass. Let me explain it to you.

The progression of apertures goes like this: f1, f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22, f32. The amount of light passing through a lens at a given aperture is double the amount passing through it at the next aperture (so a lens set at f5.6 allows through it twice as much light compared to f8). So the lower the f-number, the greater the lens's light gathering ability. Most standard zoom lenses that you'll find on a consumer-level camera have apertures between f3.5 and f5.6. f3.5 falls half way between f2.8 and f4. So they gather a lot less light than the Noctilux.

But these days, most lenses are fitted with some form of image stabilisation or vibration reduction (VR) technology, which allows the user to take sharp photos without risk of camera shake. The VR on my standard kit zoom (18-55mm f3.5-f5.6) offers an extra three to four stops of shutter speed before camera shake becomes visible. And so, in terms of being able to hand-hold a camera so as to produce a blur-free image, f3.5 becomes the new f1. (For landscapes at least; VR does not prevent motion blur of, say, a person running)

So enough of the theory - onto the photos below: ul. Pozytywki and the pond, still covered with ice despite two weeks of temperatures above zero. Photos hand-held at around 1/6th of a second exposure with an f3.5 aperture. With a Noctilux, I'd have been comfortably shooting 1/75th of a second at f0.95. Would you be able to see the difference?

This time last year:
Fides quaerens intellectum

This time three years ago: This time two years ago:
To the Devil with it all! - short story, Part II

This time three years ago:
Building the bypass as the snows melt

The time four years ago:
Two weeks into Lent


Marcin Brzezinski said...

Fast apertures are mainly used to achieve lovely bokeh (background blur), using them for fast shutter speeds is counterproductive as you effectively get nothing in focus :-)

Depth of Field on 0.95 will be in centimetres at a few meter distances.

Michael Dembinski said...

Bokeh is fine if you're into portraits, not so clever in landscapes... I've never owned any lens faster than f1.8; I've borrowed f1.4 lenses but never really felt the need to use them wide open. They tend to be soft at that aperture anyway.

Sigismundo said...

Wonderful photos. But for night-time photography, all you really need is a tripod...

Sigismundo said...

Some of your pix are quite grainy. I suspect a tripod would eliminate the need to use high ISOs. Not very convenient, tis true. But that's the laws of physics.

Sigiismundo said...

On a completely different tilt entirely, I notice your pix are very yellow, clearly the result of sodium light. Is there any way to get rid of this, to produce a more natural 'night-time feel' (whatever that is) to the images? What setting would you use? Or is it necessary to post-process the colours?

Just a thought.

Michael Dembinski said...

@ Ziggy

NOT having to lug a tripod around is the whole point; tripods kill spontaneity. Here's a snap I took nearby on a tripod...

Click here for a photo taken nearby using a tripod (25 seconds at f22).

The yellow "sodium spew" as Sir John Betjeman called it has been toned down somewhat (I desaturated these pics using Adobe Lightroom by 6%); to my eye - and this is subjective - it becomes a more accurate depiction of what I saw and felt at the time.

Anonymous said...

The reason for extremely fast apertures is "separation": subject vs background. Some call it "pop" or "3D pop".
Low f-values do not guarantee pleasing bokeh though.
Night exposures are usually done with slow apertures and long exposure times to achive reasonable depth of field (20 seconds may be needed for city panoramas etc).