What is wrong with f22

[fld]

<p>I have an antique Cycle Poco no. 5 which takaes 5x7 plates. It was intended to be used by bicycle tourists circa 1895 or so. The lens that cam standard on it stops down to f256. 'Nuf said!</p>

[Mary Doo]

<p>If max depth of field is your desire, F/22 is fine - really. A rule of thumb for me is to use the F-stop that is one below the smallest aperture. For example, if the smallest aperture is F/32, then I use F/22; if F/22 is the smallest, I use F/16, etc. Usually, the smallest aperture does not provide the best result. It is fine. I would rather be picky on other areas.</p>

[patrick j dempsey]

<p>Edward,<br>

Actually, it's a COMPOUNDED effect! With an 8x10" negative you can safely use an aperture with a much larger f/number than with 35mm film (or digital APSC) at both zero enlargement (to make an 8x10" print) and at very great enlargement. If diffraction effected all formats in the same way, then all formats would have the same diffraction limits. In other words, if diffraction affected all formats the same, then Ansel Adams's f/64 negs would have been mush at zero enlargement! Because of the compounded effects of negative size and aperture number, the opposite is found, that large negatives shot at large f/numbers can be scanned and massive amounts of detail can be rendered out of small sections of them.</p>

[patrick j dempsey]

<p>Mary, how do you know that? Harry has never in this post stated what format he shoots. If he is shooting on 4/3's or even smaller PNS formats, than we can easily conclude that his f/22 shots will be inferior to f/16 shots. And if he is shooting 8x10" then f/22 might be a more open than he should go for best sharpness!</p>

[david_henderson]

<p>If you dispute or don't understand the influence of diffraction on overall sharpness why don't you resolve it yourself, and for your own purposes, by making two prints, the size you most often make, from two static originals at f22 and f8, shot from a tripod. See if you can see any difference and whether you like each one the same.</p>

<p>The tripod is important because the f22 exposure will be considerably longer than the f8 and you'd want to take camera movement out of the equation. The static subject is important because you'd want to take differential subject movement out of the equation. </p>

<p>If you can't see or don't care about the difference, just click away at f22, forget about diffraction and leave the question of "how sharp is this lens at fxx" to those of us who actually think its quite important. There are some people who</p>

 

<ul>

<li>actually believe all the stuff written about lenses being less sharp at their smaller apertures; whether they actually understand the physics of diffraction or not is not very important.</li>

<li>print large enough to see that in practice</li>

<li>Want to have some selected parts of their images in sharp focus and some parts less sharply focussed as a compositional tool. Those people don't actually want to maximise dof all the time and consider that there is more to photography than striving for everything to be in sharp focus right across the frame.</li>

</ul>

[mike dixon]

<p>If maximum DOF is more important for the image than maximum resolution, stop the lens all the way down to its minimum aperture. If maximum resolution is more important, don't. It's a fairly straightforward matter of assessing priorities.</p>

[lex_jenkins]

<blockquote>

<p ><a href="../photodb/user?user_id=313114">John Elder</a> , Nov 26, 2009; 08:14 p.m. (<a href="admin-edit-msg?msg_id=00V6zj">edit</a> | <a href="admin-delete-msg?msg_id=00V6zj">delete</a> )<br>

I suspect a troll...</p>

</blockquote>

<p>Oh, what sad times are these when passing ruffians can say "troll" at will to fellow photographers. There is a pestilence upon this land, nothing is sacred. Even those who arrange and design shrubberies are under considerable economic stress in this period in history.</p>

<p>Several years ago Pop Photo mag published an article with macro photos of tiny sea shells taken by a fellow who violated two (possibly three) sacred rules:</p>

<ol>

<li>He stopped his Zuiko macro lens down to f/32</li>

<li>He handheld the shells and camera. No tripod.</li>

</ol>

<p>I don't recall whether wearing Speedos while wandering around beaches searching for opportunities to violate two sacred rules also violated another rule, but it probably should have.</p>

<p>On the other hand, that fellow's photos were published in a magazine while mine, correctly taken at f/16 from a tripod, have not. And I've never worn Speedos.</p>

[railphotog]

<p>I've personally taken many photos at f/22 and at much smaller apertures with a home made pinhole aperture (around f/95 I guesstimated) mounted in a 28mm lens. I did this for my model railroad photos, obviously to get the great depth of field. I realised that images taken this way were not as sharp as those taken with prime lenses opened wider, but the overall effect I wanted needed the smaller apertures. </p>

<p>Nothing like having a scale human figure about half an inch tall almost touching the front of the lens in acceptable focus, as well as the rest of the scene. Viewed on their own, my pinhole photos were acceptable, which was my goal. Several of my pinhole aperture photos were used as cover shots on hobby magazines, and many others were published in my articles, as were many using f/22.</p>

[garydem]

<p>i suspect the reason that lenses have f stop to f22 is holdover from the film days. also, for some lenses, those that can be used on both digital c sensor and FF sensor, the point of diffarction is not going into come into play at the same fstop. diffraction is what happens to light when it passes through a small hole. it diffracts or distorts. this reduces image quality. whether you can see this or not depends on you and is another matter. the charts on this webpage give a diffraction chart and show the fstop where the image/sensor becomes diffraction limited.<br>

<a href="http://www.tawbaware.com/maxlyons/calc.htm">http://www.tawbaware.com/maxlyons/calc.htm</a><br>

lenses do have a sweet spot for best performance. all fstops do not give tjhe same IQ. a low fstop(f1.4) will let in a lot of light but the lens simply is not performing at its best. conversely, a high fstop(f16-22) the lens will supply at lot of dof, but again due to diffraction the IQ is not the best. it is up the the photographer to decide which of the tradeoffs are acceptable. the lens sweet spot is between f5.6 and f11.0. below or above this range the IQ is falling off. personsally i try to keep the fstop in this range. also, THE FSTOP of best performance is also in this range. if your dslr has an adjustable program line, the algorithm is set to keep the fstop in this range if you set the program line to MTF.</p>

<p>lastly, it is simply not true that to get good dof you have to use a fstop at or beyond f16.0. you should check a dof table to see exactly what you are getting in terms of dof. i shoot my macros at f11.0 and have plenty of dof. for one thing there is a difference betwen the dof amounts using various sensors. a c sensor will give about the same dof as a FF sensor but at 1 fstop less, that is a c sensor at f11.0 is about the same dof as the FF at f16.0 this can be checked at the following website. so it is not necessary to crankup the fstop to f16-22 thinking you really need it, you do not. besides the advantage of a dslr is to be able to control the dof rather than simply shoot all the time with the max.<br>

<a href="http://www.dofmaster.com/dofjs.html">http://www.dofmaster.com/dofjs.html</a></p>

[BrianS1664879711]

<p>"<a href="../photodb/user?user_id=573251">Lawrence Dawson</a> <a href="../member-status-icons"></a>, Nov 27, 2009; 12:15 a.m.</p>

<p>I have an antique Cycle Poco no. 5 which takaes 5x7 plates. It was intended to be used by bicycle tourists circa 1895 or so. The lens that cam standard on it stops down to f256. 'Nuf said!"</p>

<p>FYI. It is likely that your shutter is U.S. stops, not F stops. US 256 is not the same as f/256. It is equivelent to f/64.</p>

[jpo3136b]

<p>You can't use f/22 just like you can't use fifth gear in your car: when you drive the equipment <a href="

an old lady.</a> Besides, that f/22 setting is right next to that focus ring which has a lot of travel in it, but that should only be set to hyperfocal.</p>

[kelly_flanigan1]

<p>There is still alot of folks totally confused here about diffraction.</p>

<p>*****It is what one WANTS at the fstop being used; it is a GOOD THING.****<br>

<br /> ****If one is using a lens at F22; F11 or F8 etc one WANTS THE LENS TO BE DIFFRACTION LIMITED.****</p>

<p>That means the lenes is as good as it gets; ie abberations quashed.</p>

<p>Being diffraction limited means one has a good lens; the ultimate goal.<br>

<br /> If somebodys says do not use F11 or F22 because there is diffraction; they are totally crazy.<br>

<br /> Its like saying do NOT move to Riverdale; because there are no taxes free water; electricity; sewer and cable.<br>

<br /> Saying one DOES NOT want a lens to be defraction limited is like saying one wants more taxes; a lower paycheck; all sorts of fees and bills; ie you are nuts.<br>

<br /> IF a lens is difrraction limited at say F22; F16; and F11; then the faster fstop of F11 has a smaller spot size; ie better resolution on film usually; if the film is decent.<br>

If some yoyo did a CLA on your lens and left out some shims; or got elements cocked; or reversed them; then the sweet spot of best performance shifts to the slower fstops; since old Kilroy goofed up your lens. A poor lens or ruined one often needs to be stopped down more.<br>

<br /> In actuality a lens often has a broad region were performance peaks; over several fstops. With a typical 50mm F2 lens it might be between say F5.6 to F11 on many lenses. Many folks shoot images of NOT brick walls; but 3D objects; thus one often stops the lens down to get obejcts at different distances in focus. Thus sometimes folks use say F22 or F16 as a compromise; one drops the ultimate brick wall resolution to gain more objects in focus; at different distances.<br>

<br /> This whole subject of the tradeoff off ultimate sharpness versus DOF versus slow blur with slow shutter speeds is as old as photography.</p>

[Tim_Lookingbill]

<p>I tested the diffraction on my cheap $80 Pentax K100D 18-55mm kit lens against a cheap $30 used manual focus Pentax 50mm-A f/2 prime lens. </p>

<p>On the kit lens at any focal length f/8 gave the sharpest results and softened gradually adjusting aperture up or down.</p>

<p>The prime was extremely soft wide open, even worse than the kit lens at the same focal length and wide open. However the prime lens gave superior sharpness over the kit lens at f/22 through f/11. </p>

<p>This goes against the sensor size claim affecting diffraction. But I still don't know what explains the difference between the prime and the kit.</p>

[patrick j dempsey]

<p>Why would you test an f/2 lens wide open against a slower... f/4.5? f/5/6? lens wide open? </p>

[randrew1]

<blockquote>

<p>*****It is what one WANTS at the fstop being used; it is a GOOD THING.****</p>

</blockquote>

<p>I disagree. A diffraction limited lens is as good as you can get, but that doesn't mean diffraction makes your pictures look better. Diffraction is what turns the image of a star into an airy disk. A smaller airy disk is better than a large airy disk so a wider aperture (which has less diffraction) will produce a sharper image at the focal plane. </p>

<p>JDM had it right. Diffraction is related to the actual width of the aperture, not the f/stop. If your aperture is smaller than 1 mm wide, you will start to see some effects of diffraction. You can see the effect at larger apertures if you look hard. When the f/stop equals the focal length, the aperture is 1 mm. I once visited a studio that shot furniture. They routinely used f/128 to get the depth of field they needed with their 8x10 cameras. Since the lens had a focal length of something like 250 mm, the aperture of about 2 mm was not a problem--especially with this large format that doesn't require enlargement. </p>

<p>For anyone who has a Kodak XL movie camera, look at the aperture as it stops down. There is an ND filter on one of the aperture vanes. This was done because with ISO 160 movie film shot at 1/28th of a second, you need f/45 in bright sunlight. The resulting aperture of 0.2 mm would produce so much diffraction that the image would be unrecognizable. With an ND filter to attenuate the light, the smallest aperture was about 0.5 mm (not great, but good enough for super 8 movies). </p>

<p> </p>

[Tim_Lookingbill]

<blockquote>

<p>Why would you test an f/2 lens wide open against a slower... f/4.5? f/5/6? lens wide open?</p>

 

</blockquote>

<p>To check softness roll-off by aperture setting and the degree of softness between two lenses so I know their characteristics and what to expect when shooting out in the field.</p>

[Ed_Ingold]

<p>To Ron Andrews and JDM...</p>

<p>The diameter (d) of the Airy disk is as follows, where λ is the wavelength, F is the focal length and D is the diameter of the entrance pupil. You should recognize that F/D is numerically equal to the f/number.</p>

<p>d = 1.22λ*F/D</p>

 

[kelly_flanigan1]

<p>I see folks new to optics are still confused.:)<br>

<br /> This happens ; one is in the circle of confusion! :)<br>

<br /> (1) ARC ANGLE If one has a telescope and one views stars; then aperture matters; ie a 6" diffraction limited telescope will have double the resolving power of a 3" telescope. What folks confused about; is faulty logic; is a point light source like a star cannot be magnifed. With a telescope resolving power is to split double stars; ie it is about ARC ANGLE.<br>

<br /> (2) LINES PER MM ON FILM With a real image on earth like a test chart or your kids; it can be magnifed. In this case the fstop boxes in the resolving power in lines per mm on film. This is covered in Sam Browns 15 cent Edmund books of 1/2 century ago; and in Kodak books of 70 years ago; in all the optics books of the last century. Its basic optics I learns as child; but today is rocket science on this thread.<br>

<br /> For a diffraction limited lens the rule of thumb 1/2 century ago was about 1500. Thus a difraction limited lens at F50 only can put 30 line pairs per mm on film best case; with a perfect brick wall test. It doesnt matter what the focal length is. Sadly I understood this in grade school; but today many cannot fathom this. This points to the decline in education; decline in the USA manufacturing base. The Kodak books and Sam Brown books were something like less than two bits then.<br>

<br /> A lens that is diffraction limited at F22 and also is diffraction limited at F11 will work better at F11 due to simple optics; the factor is 2; something worked out many centruries ago, A crummy lens also might be the same or better at F22 than F11; since the lens has alot of screwy abberations; of a duffus did a poor CLA and ruined the lens.</p>

<p>F22 is like a lawn mower set to 2 inches; whether it is OK depends on what one is doing.<br>

<br /> A setting of F22 is what our process camera was used at for about 1/3 century; process lenses are NOT flat field lenses as preached on photo.net; one stops them down to get good corners.<br>

<br /> F22 typcially is OK with a LF shot since one doesnt magnify much; and is poor for a cellphone cam or tight pitch digital sensor. In like matter a razor blade needs to be sharper than a mower blade.<br>

<br /> Resolution can be either in arc angle or physical thing like line pairs per mm on film. Both a 50mm and 200 mm lens can be diffraction limited say at F16; maybe we get about 50 line pairs per mm on film in a real work test. BOTH measure in as 50 line pair per mm; BUT the 200 has 4 times the ARC ANGLE resolveing power at F16; since its focal length is 4 times the 50mm lens's.<br>

<br /> I how I rattled some grey matter; stuck with turkey and dressing!</p>

[hjoseph7]

This reminds me of a teacher I had back in the days. Whenever I used flash on an image, she would totally freak out ! It didnt matter that I paid $450 for my flash...

 

 

Signed:

Gomer Gumph

[mike dixon]

<p>Why would it matter how much you paid for the flash?</p>

[lex_jenkins]

<blockquote>

<p>"Why would it matter how much you paid for the flash?"</p>

</blockquote>

<p><a href="

changes everything</a> . At least when one's vision is diffraction limited; abit; thus resolving errors; alot of screwy abberations.</p>

[randrew1]

<blockquote>

<p> At least when one's vision is diffraction limited;</p>

</blockquote>

<p>I know this was in jest, but it brings up a good question: Is human vision diffraction limited? I din't think so, but I don't know for sure. </p>

[kelly_flanigan1]

<p>With the Human eye that has a cataract starting in the center; it might be say say 2 to 4mm in size. In this case one has the weird condition that performance is now worse when the iris is stopped down; since now one has the glob of cataract mostly in the center; where it was once clear. Thus the optimum fstop shifts to a faster one when one has a central obstruction; thus that is why some old folks use sunglasses in non bright light and see better; than if the iris is stopped down. The same thing can happen if one dabs some goo on teh center of a filter and places it on a camera; or if one has a giant defect in the very center. The cataract also sort of a yellow filter too; thusif one makes prints for a client with cataracts; the *blues* are now darker and there is less contrast in the print too.</p>

[jeff_livacich]

<p>In response to the original question and in line with what Mike Dixon said: nothing's wrong with shooting at the smallest apertures if you need depth of field and are willing to tolerate some loss of overall optical quality.<br>

It's the same with shooting wide open: you will sacrifice optical quality compared to that at optimal aperture to gain something else, like the ability to capture an image without motion blur, minimize a distracting background, etc. At full aperture there are several problems like aberrations, illumination falloff, and field curvature, that can be minimized by stopping down. So it's recommended to not shoot wide open if you don't need to. But if you need to for say, shooting handheld or want to for something like shallow DOF, there's nothing wrong with it.<br>

So, from that standpoint, there is nothing "wrong" with f/22. What's wrong with f/22 optically has been well explained, I think.</p>

[jeff_livacich]

<p>Lex said: "And I've never worn Speedos."<br>

Thus sparing others from having to look at your perpendicularity. ;^D</p>

<p>Q: What's worse than seeing a fat guy naked?<br>

A: Seeing a fat guy wearing a Speedo. #^P</p>