Is a lens fast enough? A way for digital shooters to answer.

[Godfrey]

Having made photos for 35 years before a digital camera I could afford to touch even existed, what determines if a lens is fast enough is simply determined by answering:

Does it fit my camera?
Can I afford it?
Is it light enough to move?

😀

Seriously, in those 35 years of photography and in the ensuing 20 years of photography that followed, I've only occasionally had lenses faster than f/2.8 maximum aperture to work with, other than normal lenses for 35mm cameras. Most of my exposures, for sure, have been made at the f4 to f/8 aperture setting for 25, 50, 100, 125, 200, 250, 320, 400, 640, and 1000 ISO films. I've rarely pushed films more than one stop ... two at most so 1600 maybe ... because quality gets to be so crappy it isn't worth taking pictures—at least with small format cameras.

I'd advise, rather than calculating this and worrying yourself about that, just wait for your camera and lens to arrive, load the camera, and go learn how to shoot with it. I shoot with the Leica M-D and normally use a Summicron 50mm f/2 lens. I almost always have the lens at f/2.8 to f/5.6. I set the ISO to 400 90% of the time. I meter, set the exposure I think is right on that basis, snap, and move on. I get lots of great photographs that break any rules of calculation or correctness.

BTW: When shooting film, you normally put the slowest film you can get away with in the camera based on the available light. Daylight: 50 to 100 ISO. Nighttime: 400 to 1600 ISO. 🙂

That's photography.

G

Leica M-D + Summicron-M 50mm f/2
ISO 1000 @ f/3.4 @ 1/60​

 

[Richard G]

My fastest lens is a 28/2.8 at ISO 320. I can hand hold down to 1/15th provided the subject is stationary, and sometimes go down to 1/8th with acceptable (not excellent) results. After that, I'll put down my camera and pick up a beer.

One other point to think about:
Lets say I'm at 1/15 and f/2.8 and you're at 1/60th and f/1.4 and in both cases the subject is moving a little. Is it better to have a uniform motion blur over the whole image, or miss focus as the subject moves in and out of the narrow plane of focus?

Personally, I find people shots at wide apertures like f/1.4 are hit and miss unless they are sitting for a portrait or my shutter speed is high enough to stop the subjects motion (not my camera motion), or about 1/250. I pick uniform motion blur.

For the record, my best shots have been shot at f/4 to f/8 with shutter speeds down to 1/30th.

What a great point.

My most used film camera at the moment is a IIIf with an f3.5 collapsible 50mm Elmar. It worked for our ancestors.

 

[David Hughes]

Hi,

It's mostly a matter of technique with you, rather than a built in computer, doing the thinking. Slow shutter speeds need a technique in which you stay steady and breathe carefully and then squeeze the shutter at the right point. Once mastered you can usually get it OK at one or half a second but it gets worse as you age. And, of course, you can always jam the camera against something solid.

I used to do a bit of pistol shooting and the same applies there and pistols recoil and jump about when you fire but it can be done. Again you just have to learn and practice the right technique.

In your shoes I'd start with easy subjects and learn and get the feel of the camera and film before the more difficult subjects. Luckily there's more than enough old secondhand books about dealing with film photography and so on.

Regards, David

 

[Arbitrarium]

I used to use a 1.4 lens on my main everyday camera and often used the widest aperture, but since then I've been using f/2 or slower lenses and not felt like I was missing out, and I shoot plenty at night. With a leaf shutter, I shoot down to 1/8th of a second (or on my Retina, 1/5th) and am happy with the results, but I'm not obsessed with sharpness so a hint of motion blur doesn't bother me.

 

[David Hughes]

Hi,

I worry about this; "I can run the same analysis for a 50mm F/2.5 and see that shooting ISO 400 film gets me a little below EV 7. That makes it more than passable for daytime outdoors work and portraits, which, again, is probably good enough for me as part of a small kit. F/2 would get me even further." I can understand this, BTW, as we all worry before committing out money to some unknown article.

A lot of us grew up using 25 or 50 or 64 ASA (meaning ISO) slide film and with cameras with f/4 lenses or f/2.8 because f/2 lenses were unaffordable. You'll find that the (?Minolta) CLE has an f/4 portraiture lens (from memory - so beware) and few complain about it, if any.

I think part of the problem is that digital cameras are sold by emphasising numbers and they give a completely wrong impression, according to this old idiot. With film cameras you usually end up loving one version of film for colour and one for B&W. And if the film has an ISO of 125 or 64 you learn to work with it. Look at the history of Kodak slide film and you may see what I mean. I can think of a film as fast as 25 ISO that people would kill for...

Anyway, that's just my 2d worth. And may I add that you don't get an EXIF with film cameras? You can get around that by using a notebook and pencil. It's a great learning tool.

Regards, David

 

[karateisland]

Hi,

[...]

You'll find that the (?Minolta) CLE has an f/4 portraiture lens (from memory - so beware) and few complain about it, if any.

I think part of the problem is that digital cameras are sold by emphasising numbers and they give a completely wrong impression, according to this old idiot.

[...] And may I add that you don't get an EXIF with film cameras? You can get around that by using a notebook and pencil. It's a great learning tool.

Hi David--Good points. Thinking more on your argument, I remember that I shot film for a few years about a decade ago using a 50mm F/2 lens (I think?), and I recall learning to work with that lens and never feeling like it was a burden. Since then, I've certainly fallen prey to the idea that bigger/smaller numbers make better photographs, when we all know it's the photographer who makes the photograph.

I suppose part of the idea with this experiment was to turn my obsession with numbers into a net positive: Here, the numbers are telling me that I don't need to worry myself about getting the fastest lenses around. A more assured photographer might not need this help, but it definitely did the trick for me. That is, I will definitely be buying the F4 90mm for my Minolta CLE and can't imagine I'll end up complaining.

The whole thing reminds me of buying a stereo a few years back--After a lot of research, I had convinced myself I wanted a pair of Harbeths, which are in the same league for audio as Leica glass is for photography. While I saved for these extremely expensive speakers, I purchased a set that cost 1/10 as much in an effort to tide myself over. Wouldn't you know it, these speakers turned out to give me 100% of what I needed. That extra money is going toward my photography now.

And, for what it's worth, I have my notebook and pencil ready in my backpack for recording notes on my film!

 

[karateisland]

Leica M-D + Summicron-M 50mm f/2
ISO 1000 @ f/3.4 @ 1/60​

By the way--gorgeous shot!

 

[willie_901]

Simulating exposure based on film media is problematic

Simulating exposure based on film media is problematic

I do not find F2 to be a limitation with the newest APS-C cameras. This is because my work usually requires wider DOFs.

With a digital camera all you can do is maximize exposure. When DOF is not a consideration, wide apertures are important because they are more flexible. Fast lenses have more surface area. When the lens is wide open more light (signal) can be recorded by the sensor for a given shutter time. However as the need for DOF increases, the advantage of a fast lens (in terms of S/N) decreases.

The way to maximize exposure with raw files was explained by Emil Martinec.[1]

"Maximize Exposure; maximize subject to three constraints:

(1) maintaining needed DoF, which limits how much you can open up the aperture;

(2) freezing motion, which limits the exposure time;

(3) retaining highlight detail, by not clipping wanted highlight areas in any channel.

Note that ISO is not part of exposure.

Exposure has only to do with aperture and shutter speed. Maximizing exposure guarantees that one captures as many photons as possible subject to photographic constraints, and therefore optimizes S/N.

How does ISO enter?

It enters as a subsidiary aspect of optimizing S/N.

On many cameras ..., there is little or no advantage to raising the ISO, which aids point (3) -- leaving the ISO at a low value may leave the histogram "to the left" for your chosen exposure, it will give more highlight headroom but will not degrade S/N; such cameras can safely be operated at close to their lowest ISO (the precise optimal ISO depends on the details of a given camera design). On the other hand, for many other ...cameras, ... noise relative to exposure is improved by increasing the ISO; after you have maximized the exposure (ie by satisfying criteria (1) and (2)), you have a tradeoff to make for (3) -- raising the ISO lowers shadow noise (up to a camera-specific point of diminishing returns, usually about ISO 1600), therefore improving S/N, but reduces highlight headroom for your chosen exposure, so one has to decide how high the ISO can go and still keep wanted highlights unclipped.

Anyway, the prescription is to set the exposure (shutter speed and aperture only) according to (1) and (2); back off the exposure if at base ISO and you are compromising (3). If you are compromising (3) with your chosen exposure and you are not at base ISO, then you should have started with a lower ISO. Afterward, depending on the specifics of the camera's noise profile, further optimization results from raising the ISO, up to the limit specified by (3), or the camera's ISO point of diminishing returns, whichever is arrived at first."

This exposure technique can be quite different from simulating how one uses a film camera. For one thing, the light meter is only critical to avoid clipping highlights. With raw files intentional underexposure is not necessarily bad as long as the S/N (exposure) was maximized. An aesthetically appropriate global rendering brightness is achieved during post-production.

For in-camera JPEGs the film analogy and light meter usage is relevant. However the convenience of in-camera JPEGs has a potential price. The image S/N may not always be optimal because the ISO required for acceptable in-camera image rendering brightness may degrade the S/N compared to a lower ISO setting.

Another consideration for you is the S/N vs ISO profile with you FUJIFILM could be different than the CLE's. It is possible enjoying the best low-light image quality with the CLE will require different ISOs because the two cameras' noise profiles are different.

[1] A direct link to Prof. Martinec's post has been censored in the past as it was appeared in another photography Forum.

 

[Godfrey]

The downsides of using Emil's strategy are that you have no way to accurately gauge whether your capture succeeded since the in-camera image is unviewable when reaching the limits of exposure, forget about taking advantage of the metering system of the camera to determine correct exposure, and the range of adjustment possible in the raw converter (which has its limits too).

Utterly unnecessary in the world of modern sensors, it was useful 15 years ago when he proposed it. Sensors today have both more dynamic range and more sensitivity than you need 90% of the time so there's little need to dogmatically always maximize the curve on the right of the histogram.

And it has NOTHING to offer when it comes to film photography.

G

 

[f16sunshine]

To try and re-iterate my previous point in fewer words.

Go where the film/lens takes you.
It's not digital where your camera may be capable of adapting to nearly any light level.
With a film camera, the photographer is there to bring back what is available.
After some familiarity, you'll know when to lift the camera or whether it's time rather to set down the camera and lift a beer (as Michaelwj says nicely).