Does diameter of the lens (filter size) matter?

<p>Dear All,<br>

I wanted to know if diameter of lens, i.e. filter size, made any difference in the quality of the picture. For e.g. a regular EF 70-300 mm lens has a filter size of 58 mm and the same L-series lens has filter size of 67 mm. <br>

Your feedback will be appreciated.<br>

Regards,<br>

Gurpreet. </p>

<p>The 58mm filter is cheaper than 67mm so it may matter to your credit card balance! If both lenses have the same focal length and aperture, the larger filter will have a little more clearance around the diameter of the front element. For telezooms this doesn't matter much. However for wide lenses you have less chance of vignetting or may be able to stack filters on the larger threads.</p>

<p>Of course if you choose the same sized filter thread size as your other lenses, you can share the same filters, i.e., not have to buy duplicate sets or stepup rings.</p>

<p>Filter size does not determine image quality. However, generally the lenses with the highest image quality are also the fastest lenses available which requires a larger diameter and hence larger filter sizes.</p>

<p>2 cents worth.</p>

<p>Does more cubic inches (or CC) mean more horse power? Not always but .....</p>

<p>OK so lens is a square function not a cube function, less dramatic but same theory should apply also, same FL and fstop. :=)</p>

<p>Many "pro" lenses have 77mm filter rings. This is, in part, due to the larger front elements that come from having a faster lens (or a continual aperture lens on a zoom) ... but it's also something of a standard, which means you save money on things like CP, ND or GND filters because you can share them between lenses. That way you can buy the best ones made and still be ahead of the game.</p>

<p>"I wanted to know if diameter of lens, i.e. filter size, made any difference in the quality of the picture."</p>

<p>No.</p>

<p>There are theoretical reasons why a larger front element can lead to higher IQ, apart from the issue of faster apertures. Basically, the more photons in your optical pipeline, the higher the signal to noise ratio. This is said to be the reason the EOS mount has such a large inner diameter. In comparing any two random lenses, this factor is probably overwhelmed by the many other choices the lens designer must make.</p>

<p>Still, when you look at the F/4 L zooms, you see that they all have bigger front elements than a good consumer zoom of simular range, even when the consumer zoom is slightly faster. So I think the OP may be onto something here. Insofar as filter size is a rough guide to the size of that front element, then maybe size matters.</p>

<p>Bigger glass, more money.</p>

Dr. Path, the S/N issue you mention is unrelated to thus question, unless you can provide some evidence that you'll

get less noise from a f/4 exposure on a "large inner diameter" lens than from a f/4 exposure on a different lens.

Basically this is nonsense.

 

The reason that some "consumer zooms" have smaller front elements (besides their smaller maximum apertures) is

that they are variable aperture lenses that do not provide the same large aperture at longer focal lengths.

 

The answer to the OP's question above whether there is a cause and effect relationship between larger filter ring

diameter and image quality is still "no."

<p>In reply to G. Dan: I'm a pathologist, and I take photomicrographs of my cancer cases to show to the surgeons and oncologists at our cancer conferences. The 40x objectives of Leitz and Zeiss microscopes I use have diameters of 2 to 3 millimeters. Because of this, these very high quality microscopes can only deliver 2 or 3 megapixels of information. This is a well known problem in my hyperspecialized area of photography.</p>

<p>Now, it is obviously an extreme example to compare these microscope objectives with my 17-40mm f4L and its 77mm front element. The point is that there is a real physical principle here, which the OP has chanced upon. Does this matter, with most cameras, and most lenses now in use? Probably not, as I remark in my first post. As you point out, the constant aperture zooms have to have larger elements. Will this remain the case? I doubt it.</p>

<p>Erwin Puts wrote an article on the future of lens design a few years ago. In it he argued that the increasing resolution of digital sensors was going to require much <em>bigger </em>glass. With ever increasing numbers of pixels, each requiring a minimum number of photos to overcome S/N limits within the time of exposure, the more photons you suck in the better. I wonder if we are already seeing this factor in the new generation of 40, 50, and 60 Mp MF backs. The pixel pitch of these backs is not that impressive, compared to current 20-something MP FF cameras from Canon, Nikon, etc. So why do their images look different? Maybe it's that big MF glass.</p>

 

<p>Thank you all for your honest opinion and sharing your experience with me. I truly appreciate every feedback.</p>

<p>The point of the "bigger glass" argument is not that, to get back to the OP's question, that larger diameter front elements (and correspondingly larger filter diameters) have any correlation whatsoever with better image quality.</p>

<p>You are extrapolating from some true fact to come up with an incorrect conclusion. The signal to noise issue arises with smaller photosites as sensors are made smaller and/or filled with more densely packed photosites. The theoretical argument is that you will, if all else is equal, have a smaller S/N ratio in a system with smaller photosites and that (we've heard this a lot) increasing photosite density will produce serious problems with noise.*</p>

<p>A fundamental flaw in your extrapolation is the following. Let's try to follow your logic. Photosite density is increasing. When photosite density increases, the S/N ration drops.* In order to avoid noise it will be important to get plenty of light onto the sensor. Larger apertures will get more light to the sensor.</p>

<p>Well, yes. But so will longer exposures, and without the <em>other</em> image quality concerns (which are quite real) that come with the use of extremely large apertures: corner softness, very shallow DOF, to name a couple.</p>

<p>In any case, none of this is about the ability of the lens to deliver a fine image to the sensor, much less the size of the front element and much less than even that about the filter diameter. </p>

<p>Dan</p>

<p>* Your final point about MF digital backs is related to the asterisk I added to my text above. Let me start with DSLR history and then extrapolate to MF digital systems and our assertions about them. When DSLRs advanced from 6MP to 8MP there were those proclaiming (often rather loudly and insistently) that this increase in photosite density would lower the S/N ratio and lead to unacceptable levels of noise. (I missed the earlier transition from something with even lower photosite density to the 6MP level, but I'm confident that the same claim was made about the 6MP sensor.) Then we saw newer cameras announced that would have 10 MP or 12 MP sensors, and the same worried claims were made about the degradation of image quality that would surely come from the higher photosite density. We saw it as cropped sensor bodies increased to 15-18 MP ranges, and we saw it as FF systems were announced that had 20+ MP sensors.</p>

<p>We have now had plenty of opportunity to test the accuracy of these claims, and they have been found wanting. If they were correct, and the image quality had degraded each time the sensor density increased we would all be buying some pretty pathetically awful DSLRs today that could only have been increasingly worse than the cameras from the 6 MP era. But that hasn't happened. The vast majority of photographers of all types have embraced the continuously increasing image quality produced by the higher density systems and we have not seen, for example, a steady deterioration of the ability of the 1Ds system cameras to produce excellent images.</p>

<p>You don't have to "wonder" about the new generation of 40, 50, 60 MP (and now even larger) MF digital systems. There are plenty of people using them and reporting how well they work. Why do their images look different? Several explanations are part of the answer. For one thing, they are generally not shot the same way that DSLRs are shot - they are almost always shot by very experienced photographers working carefully from the tripod and heading in the direction of high end commercial or fine art work. Secondly, the format size most definitely makes a difference when you begin to push the boundaries of image quality and when it comes to IQ potential large is virtually always better. Third, and not entirely unrelated to #2, a lens of a given ability to resolve detail (as expressed in MTF terms) can resolve more detail when used on a larger format system.</p>

<p>Interesting discusion,<br>

but have a small remark/question :<br>

in general I guess this is true for zoom lenses...but less for primes?<br>

If you look at the EF 50 f1,8...in my opinion it has a small front element <br />and not really a slow lens if you ask me.</p>