Optimum f-stop

[herron]

Anyone recall the old rule-of-thumb about what the optimum f-stop of any given lens was likely to be?

I seem to recall the "third stop from the smallest aperture." That would mean the sweet spot of an f/22 would be found about f/11, an f/16 about f/8, etc.

Does anyone else remember that, or did I inhale one time too many back in the 60s?

[John Parry]

Sorry Ron - the only adage I heard about that was "F8 and be there". And in fact, my tendency has always been 5.6 and work the exposure around it.

Sorry for nothing constructive.

Regards - John

[k38]

I believe it depends on the lens design. Tessars are supposed to be best 2 stops from open, but Planars are supposed to be best 4 stops down. Large format lenses are generally corrected so that their smaller apertures are good. I am pretty sure given the many parameters of lens design: speed, color correction, distortion, flatness of field, coma, etc. that any lens design is a trade-off of one thing for another. Of course since we are in the real world you have to consider cost as well. I think you would have to experiment on each lens to really know.

Dwight

[PeterW]

Hi Ron,

I've always understood it to be the other way round, that the optimum f-stop was three stops smaller than maximum. Can't remember where I first heard it, but it was years ago. Also I have no idea what criteria were used to arrive at 'optimum'. General all-round lens performance I suppose.

With many lenses, counting down from the maximum or up from the the minimum aperture arrives at more or less the same f-stop. I also remember a generalisation that the edge definition of most lenses begins to fall off at f-stops smaller than the optimum as well as larger than the optimum.

There was another very old rule of thumb which I read in a magazine from the 1920s and which said try to keep the aperture halfway between the maximum and minimum, which amounts to much the same sort of thing.

Another one was that to lessen the chance of camera shake set the shutter speed close to the reciprocal of the lens focal length, ie 1/50 sec for many standard lenses, 1/125sec for a 135 lens and so on, and then choose the aperture to suit. This was in the days when 35mm was the accepted wide angle lens, and 1/30 or 1/25sec was the slowest most people could go and still hold the camera steady.

Most of these rules of thumb came about in the days long before computer-calculated lens design and camera stabilisation, so whether or not they still hold good with modern lenses and cameras I don't know. I suspect some of them still do.

They were aimed at the beginning photographer who had progressed from a fixed-focus, fixed aperture, fixed speed, simple camera to one with stops and speeds. Without them, many people found they were disappointed with the results from a 'better' camera compared with those they got with their first simple one. Anyone remember any more 'rules'?

My view is that as you progress and learn more you can move on from these simple rules and learn to use the versatility of your camera, something which auto-everything seems to be pushing more and more into the background, yet at the same time producing a higher ratio of 'acceptable' pictures.

The computing power of the tiny chips inside modern electronically-controlled cameras, and the programs they carry, are so good I have to admit that for general shots I sometimes get lazy and use the 'program' settings on my Canon A1 and T70 - and they're not very 'modern' cameras by today's standards!

In other words, if you keep a guard dog there's no pressing need to learn how to bark!

PeterW

[vintageslrs]

Peter and Ron

I always understood the optimum f-stop to be (on most lens) f8 to f5.6.

And on most standard lens......that would be approx. 3 f-stops up or down from their largest or smallest aperture.

;D
Bob

[John Parry]

peterw said:

There was another very old rule of thumb which I read in a magazine from the 1920s

Must have missed that issue Peter!! LOL

You are a superstar!!

Regards - John

[herron]

peterw said:

In other words, if you keep a guard dog there's no pressing need to learn how to bark!

PeterW

Thanks everyone...that certainly cleared it up for me.
LOL!!! ;D Seems we are all saying basically the same thing...sort of.

Now that I have had time to consider it longer (the neuron flash in my brain, as a response to the original thought, has had sufficient time to settle) I think you're right, Peter. I believe I did actually hear it that way...as third stop from the largest aperture, which in many cases is about the same place!



----------
And, Peter, I don't keep a guard dog, because they are always going off in the middle of the night...and I don't like the "auto" settings on cameras, because just "taking" pictures takes all the fun out of "creating" pictures!

But I absolutely love your metaphors!

[doubs43]

Going back to the days (1968) when I first became serious about photography, I picked my father's brain as he'd been seriously involved with the craft 29 years at that point in time. This is what he said:

Optimum sharpness will USUALLY be either 2 or 3 stops down from the maximum. The key word here is "usually" and Ron Head is spot on with the advice to individually check each of your lens as the rule is not carved in stone. For instance, a 50mm f/1.4 lens stopped down 2 or 3 places will be f/2.8 or f/4 and that could be optimal or not. In my experience, f/5.6 and f/8 on an f/1.4 lens are generally pretty good.

This question, I think, goes back to one of lens testing. While 2~3 stops down from maximum is generally pretty good, it doesn't hold true for all lenses and can be effected by the body the lens is mounted on. When the body is within tolerance but on the edge of being out of tolerance and the lens is on the edge in the opposite direction, you could have poor performance at maximum aperture and require 4 or 5 stops down to ensure best results.

Lens testing is ONLY good for the specific lens being tested and the identical lens a few serial numbers earlier or later could give different results. Your own lens is unique so test it to see what it's capable of doing.

The old rule of matching the shutter speed to the focal length is pretty good for most people. I have some images (slides) I took with my 50mm f/1.4 Zuiko lens wide open at 1/8 of a second HAND-HELD that were pretty good.... when I was 30 years old. I'm more than double that now and unless I trained with weights and raised my endurance level, I couldn't hold that lens below 1/30 or 1/60 now. The body does deteriorate over time.

Walker

[herron]

I agree, Walker. Any "rule of thumb" is, to me, an approximation...nothng more. Just an agreeable place to start, when specifics are not known.

And Peter's shutter-speed-to-focal-length comment is another good one, too. I can recall hand-holding shots at 1/15 in a pinch (using a 50mm lens) and being happy with the results...but that was nearly 40 years ago, and I have not been that steady in a long time. Could never have done it with a 200mm, or even a 135mm, even at that age.

[PeterW]

Ron Herron wrote@

...and I don't like the "auto" settings on cameras, because just "taking" pictures takes all the fun out of "creating" pictures!

I take your point, Ron, and agree. I'd been taking, or creating if you prefer, pictures for years before I got an auto anything, even an auto stop-down iris. But auto features can come in awfully handy when the grandchildren are around. There often isn't enough time to be creative. Same thing applies if like me, as I've said in the past almost ad nauseum, your favourite subject is people. I feel another ramble coming on.

People in their natural habitat, doing ordinary everyday things, are the most difficult animals in the world to photograph successfully, to capture an atmosphere, a fleeting look or a gesture, that makes the picture tell a story.

That's why I was first attracted to pictures by people like Henri Cartier-Bresson and Felix Man, two photographers who were my inspiration in my photographically formative years.

I can look back on literally scores if not hundreds of missed 'decisive moments' (here we go again!) because I was adjusting the aperture (manually), adjusting the shutter speed (manually), resetting the focus (manually) ... and trying to keep the subject in a tiny viewfinder.

You had to be dextrous, a master of prestidigitation (I've been longing to use that word), to be successful taking these sort of pictures with old cameras.

You really had to practice with cameras and become familiar with different light conditions until picking a viewpoint, setting the camera and taking the picture became instinctive. You didn't think about why or how, you just did it. A bit like changing gear on a manual gearshift car.

What I wouldn't have given for even half the anticipation and skill of the leading photographers in this field now, alas, superseded by equally skillful television feature cameramen. Sadly, the pictures produced by these cameramen are fleeting. You can't buy books of them to look at, study and draw inspiration.

Which is why, of course, books of pictures taken by the masters in this field of photography 30 to 80 years ago are still being published, enjoyed and studied.

And people wondered why I used to get so mad when self-styled experts at snapshot clubs - I beg their pardon, photographic societies - dismissed them as 'just documentary photography'. They weren't ARTISTIC pictures, you see.

Nowadays, such remarks go in one ear and out the other, like water off a duck's back.

PeterW

[SidW]

These basic rules might have been for beginners, but they've stayed with me mostly.

The 2-3 stops down rule presumably gives better edge definition, and a larger depth of field that might help counteract focus errors (whether inaccurate camera or inaccurate you). This would be the first rule you compromise with once you get to know the capabilities of lenses. But right from the beginning I've used tele lenses at full aperture to keep the exposure brief. But I've been spoilt by more modern lenses that are good at larger apertures. Like John Parry I use 5.6 quit a lot. Last summer, the UK Esakta Circle competition was devoted to triplet lens. I cheerfully used a Meyer Domiplan at 5.6 and was horrified when I saw results that confirmed that lens's poor reputation. Yet the winners used Domiplans too, but three stops down, not just one.

The exposure and focal length rule is sacred, I never break it. Better use a larger aperture than a slow shutter speed. As some said, age doesn't help. And asthma inhalers and other stuff from bottles doesn't make you steadier either.

One rule I had forgotten over the years was to keep the lens cap on to save the shutter blinds from burning. But returning mirrors and leaf shutters provided extra protection. I've more likely kept a cap on to protect the glass from knocks.

Another rule I've respected is use a lens hood whenever possible. Apart from cutting down reflections, it provides physical protection too. My hoods have taken severe knocks that would otherwise have hit the lens front. Look at all those e*ay lenses with dented filter rings ... This rule bcame difficult with zoom lenses, especially with a filter as well.

[herron]

sidneywood said:

....The exposure and focal length rule is sacred, I never break it. Better use a larger aperture than a slow shutter speed....

I find I like to shoot at f/8 or f/11 most of the time...and, actually, I seldom think about the "optimum" f-stop. A question that was asked of me on my own forum got me thinking about it again.

But I often use the smallest aperture and very long exposures. I prefer 100 speed print film (although I used to shoot 64 Ektachrome eons ago), and like landscape-type subjects...often shot with a tripod.

[paulatukcamera]

I used to think f8 was where I should be, but over time I found even with humble triplets, f5.6 was good enough. Then I dicovered Nikon lenses and found I could shoot wide open with no differences that I could observe!

Even projected, it was the limitations of my projector's lens rather than anything else.

However faced with a small digital and a fast zoom lens, I have been using f8 again. Completely wrongly it turns out! Read my posting on small sensors, depth of field and quality.
cameracollector.proboards30.com/index.cgi?board=lens&action=display&thread=1168468850

Evidently because the size of the iris is so small on a small sensor camera, diffraction cancels out the optical improvement. I should use f4 for best results!

Presumably this affects all your DSLRs as well, so f8 - f11 may no longer be optimum with your existing lenses.

Use the tester in the thread to see if this is true in your own case.
I know the title of my posting has put 90% of you off reading it, but I found it an invaluable article

Paul

[bobm]

However faced with a small digital and a fast zoom lens, I have been using f8 again. Completely wrongly it turns out! Read my posting on small sensors, depth of field and quality.

The published aperture range of my Minolta DiMage 7i extends from f2.8/3.5 - f8 although I have seen it indicating f9 - whatever the case, the aperture range that Minolta chose, would seem to bear the above out.

Presumably this affects all your DSLRs as well, so f8 - f11 may no longer be optimum with your existing lenses.

This would be interesting to try, if it hasn't already, on a FF DSLR.

[herron]

paulatukcamera said:

Presumably this affects all your DSLRs as well, so f8 - f11 may no longer be optimum with your existing lenses.

Paul

With the standard kit lens on the Canon 300D (Digital Rebel) the max f-stops are 3.5 @ 18mm and 5.6 @ 55mm. The lens will also stop down to f/32. If I use the RofT and move 2 stops from the max, I will still be at f/8 (roughly) and f/11....am I missing something here?