Yes, of course, Diffraction is present at every lens opening. All ye that enter here, abandon hope. Slap your lenscaps back on and take up needlepoint.

We have been operating a glass processing plant with a glass cutting table from Vetromac for the last 3 years and are very happy with the performance of the machine. The user interface is very easy to navigate and takes very little time to understand. The machine is robust and precise. It is a quality machine that we would recommend to other glass processors. To back up the product, Vetromac provides excellent after sales service.

Glasscutting machine

Laminated glass cutting unit, optional on the entire Vetromac range. User-friendly management program developed on a Multitasking platform. An intuitive graphic interface manages all machine functions in automatic and manual mode. The machine is built according to local laws.

So the diffraction limit, expressed as the distance on the film subtended by the diffraction limit angle (lp/mm), is effectively constant at constant f/a, regardless of focal length.

Breaking tables built with the same totally modular concept as the cutting machines. Available with or without hydraulic loading-unloading arm system.

Message: There is a simple relationship between f/ stop and diffraction. A PERFECT f/1 lens can project an image onto film with a resolution of about 1400 lines per millimeter (different references give somewhat different numbers). Smaller apertures give lower resolution. Some examples:

Why would you even worry about the diffraction limit at all - unless the diffraction-degraded resolution of the lens approached the limited resolving power of the film? 50-100 line pairs per mm is about the practical limit for color negative film. Stop right down to an aperture a = f/22.6 (61 lp/mm)if you want.

This is the first automatic cutting table we have purchased; it is so easy to use and gives such brilliant results that we now wonder how we managed without it. The only problem we have encountered is one which was due to operator error; Vetromac were brilliant at talking us through where we had gone wrong and the problem was solved in a matter of minutes. We have no hesitation in recommending the company and their products.

1: YES. Larger formats realize less diffraction because The actual lens opening of a medium format lens is roughly twice that of its 35mm equivalent. For example, F8 on a 35mm "normal (50mm)" lens works out to 6.25mm, whereas it's 13.125 on , for instance, Pentax's 67 105mm.

The answer to your most elemental question is one that only you can answer, Doug: "Could I go for the greater depth of field at f22 and never notice the additional loss of resolution due to diffraction?" Make an exposure at F11, F16, F22. Get them all printed in a size large enough to evaluate the distinctions, and you'll have your answer.

The point I was trying to make is that as a practical matter, the optimal point of concession to diffraction is at or around F8. Whether or not the effect can yet be detected by means of an electron microscope is not a matter that speaks to the heart.

2: NO. Diffraction is equal, regardless of format, but it's much less apparant in medium format because far less enlargement is required to produce the same size print as 35mm.

CNC glasscutting

The rule-of-thumb on this is that diffraction begins to be a factor on apertures smaller than F8, although it varies slightly from lens to lens. As for the variance from one format to another, I've heard two diametrically opposed schools of thought:

If a lens has extraordinary corrections, its best aperture can be close to wide open (expensive Canon and Nikon glass), or even wide open in the case of satellite and aerial imaging lenses. Of course really extaordinary lenses sell for corresponding prices -- expect to pay way over $100,000 for your satellite camera lens. In the case of cheaper lenses, optical aberrations limit resolution near wide open, and you will have to stop down a lot before the decreasing aberrations meet the increasing diffraction -- perhaps as much as f/11 or f/16 in the case of el-cheapo telephotos for 35mm cameras.

The loading and unloading of the glass sheet is performed by means of hydraulic arms system (26-19 pneumatic). Control panel with fanless industrial computer with WiFi and integrated 27-inch monitor, management program developed on an easy-to-use Multitasking platform, with 250 pre-built parametric templates. An intuitive graphic interface manages all machine functions in automatic and manual mode. The machine is built according to CE local laws

Well, I guess this shuts your water off, huh Pete (I'll admit that I staggered momentarily over the mention of airy discs, but a deep breath and a cup of coffee did it for me)? Neener neener.

Good god, Pete, I wanted help--but not THAT much help. Midway through your second paragraph, my mind overdosed on equasions. Were it not for the LA County paramedics and their expeditious use of oxygen, I might never have been revived.

The loading and unloading of the glass sheet is performed through a belt conveyor. Control panel with fanless industrial computer with WiFi and integrated 27-inch monitor, management program developed on an easy-to-use Multitasking platform, with 250 pre-built parametric templates. An intuitive graphic interface manages all machine functions in automatic and manual mode. The machine is built according to local laws.

One would think that the diffraction limit (as a function of f/a)changes with a change in focal length, because the same f/a at a longer focal length needs a larger aperture (a) - and we know that the diffraction limit is inversely proportional to a. A longer lens at the same f/a ought to have a larger aperture, and subsequently, a smaller diffraction limit, right? This is true. However, the diffraction limit as a function of aperture is actually expressed as an angle. When that angle is projected onto film with a longer lens, the lens is further away from the film (longer focal length), and the distance that angle covers on the film increases proportionally with the focal length.

We have a Vetromac CNC machine and we love it. We have had one of their machines in our shop for the last 3 – 4 years in our plant. They have been so helpful with everything. If there is a technical question they are quick to respond. I am so appreciative to have the team of Vetromac to call on when I need them. I would not hesitate to purchase another machine from them when that time comes up in the future. Thank you for always being there for us!

The Vetromac Team produces a great cutting table at a competitive price with the best warranty in the industry.  They really understand the essence of time and not only delivered the table by air but their continued service was the most important factor during my purchasing decision.  When or if my company is to graduate into another cutting table or a larger facility, I will have no reservations as to who I will partner with, Vetromac.

For whatever it's worth, were I you--locked in to the 6x6 format--I'd look into getting a Hasselblad Super Angulon. The ability to tilt your forward axis would probably solve all your problems.

These numbers are for perfect lenses without any aberrations. Note that these numbers are independent of focal length; it's the f/ number that counts.

Ansel Adams (Otherwise known as God Almighty Incarnate, that omniscient, omnipotent creator of the universe, and of us all), "The Camera," page 74

We have been impressed with the excellent service and quick response time for our Vetromac cutting system. The system integrated smoothly with our production software and replacing our previous cutting system with the Vetromac has significantly improved our cutting time of coated glass with the edge deletion. Vetromac also offers many add-ons that will allow us to expand our future product offerings without the large capital expenditure of an entirely new system.

"...With diffraction causing some loss of sharpness at small apertures, and certain aberrations degrading image quality at large stops, a lens usually gives its best image quality somewhere near the middle of its aperture range."