Picdude Loc: Ohio

OK. I have read and followed with interest all the threads on aperture, shutter speed, ISO, focal length, DOF, IQ, etc. The one thing that I have not seen mentioned yet on here is what, if any, effect the diameter of the lens has on image quality. Can it affect exposure or DOF? Can it decrease or increase chromatic aberration? Or is there absolutely no effect on image quality at all?

So for instance, if I take two pictures of the same subject; same distance away, same time of day, same focal length, aperture, shutter speed, ISO. The only difference between the two pictures is one lens has a barrel diameter of 52mm and the other has a diameter of 67mm. What, if any, differences could I expect to see between the two images?

SharpShooter Loc: NorCal

All things being equal(they rarely are) you should see NO difference.
Barrel diameter is mostly affected by lens max f-stop and lens design. The main objective lens at the front has to fit into the lens and there things can change fast.
Other than that the focus motors and shake system have to fit as well. Lens barrel material will also have a minor role in barrel diameter.
But if all things are equal, you should see no difference at all!! ;-)
SS

Picdude Loc: Ohio

Thanks for the fast response SS. Hadn't tried to put straight mechanics into the equation. That would also explain why it has never come up in discussions on exposure, DOF, CA, etc., etc.

Tigger1 Loc: Surrey, BC Canada

Hi Picdude;
Upfront I admit to no optics technical training, so cannot answer your question from that perspective. However, given the three lenses you do have i.e. one 52mm, one 67mm and one 58mm you could setup a few tests of your own that may give some answers to your question. But, as a matter of common sense, given that each of your lenses has different component construction in the optics and the individual lens elements within each lens differ one from the other, one would be inclined to draw the conclusion that you will generate different results given the specific parameters you have laid down in your original question.
You could easily test your 18-55 against your 18-140 using the parameters you have supplied to see what results you get at 18mm as an example. Or, test your 18-140 and your 55-300 at 70mm to see what results you get. Based upon your test results, I think you would get a reasonable answer to your question although it would be coloured to some extent by the differences in the internal composition of the tested lenses.
Best regards,
Garth

joer Loc: Colorado/Illinois

There is no direct relationship only indirect.

Apaflo Loc: Anchorage, Alaska

Think this out just a little more... ask why would one lens have a larger barrel, and then ponder the effects of the reason.

Say you have two lenses and shoot the same scene at f/4. The results are not likely to be the same! One has a maximum aperture of f/4, and as a result it is being used wide open (and maybe the reason it is being used is because it weighs less and this shot is taken while on a 20 mile hike).

If the other lens has a maximum aperture of f/1.4 it is being used at three stops down from maximum, and is probably significantly sharper than the other lens. It is also significantly heavier and the photographer who packed it 20 miles might just decide to buy an f/4 lens! :-)

There are also reasons, such as inclusion of an auto focus motor and image stabilization hardware, that have nothing to do with the optics but may have other significant effects on image production.

BboH Loc: s of 2/21, Ellicott City, MD

The only thing it will effect is angle/field of view -

Leitz Loc: Solms

You may want to re-read the question!

jerryc41 Loc: Catskill Mts of NY

Lenses with a larger aperture generally have larger glass - to get more light. They also have larger prices.

Leon S Loc: Minnesota

I am now speaking from opinion only, but aside from lens diameters being larger because more options being included, I believe that like water pipes, the larger the diameter the more light can travel through per milla second. Light acts similar to water and restricted water in pipes causes turbulence in the water flow. This seems to be a reasonable explanation for why pro lenses are larger than (cheap) lenses. Then again, I can't prove this theory. But I know this affect is present in moving fluids in pipes.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

REALLY. What an astute observation.

steve_stoneblossom Loc: Rhode Island, USA

Yes, but unlike liquids there is no pressure build up from a large(r) volume of light being forced through a small(er) opening/aperture. If you could prove that theory, then I would be wrong.

dcampbell52 Loc: Clearwater Fl

It answered his question. This is why some very sensitive astronomical telescopes have a huge diameter even though their angle of view is extremely narrow given the distance that they are viewing. Mainly, diameter of the glass is the major deciding factor to aperture diameter. Having said that, my 50mm f/1.4 is not nearly the diameter of my 10mm-24mm f/3.5-f/4.5 zoom wide but is more than twice the focal length. And my 70-300 is considerably longer but only slightly larger in diameter than the 50mm but has an f/4-f/5.6 aperture. So the diameter is (probably) a relation to focal length to max aperture. In other words, a wide long lens probably will have a larger aperture (be a faster lens and smaller DOF) than a smaller diameter lens of the same focal length. The smaller diameter lens may have the same focal length but would be unable to achieve the larger aperture because of the smaller diameter body. Thus the smaller diameter lens would tend to be less expensive if all other factors were equal. Other factors could be quality of glass, manufacturer, length of warranty, quality of build, etc.

Leitz Loc: Solms

Not to mention that lenses with larger glass generally have larger barrels, as well.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

I am amazed at the quality of the responses on this particular thread. No wonder people have flocked to this site over the years. I learn something new everyday. Keep up the good work everyone.