52mm vs 72mm, why the option?

kebwi · Jul 5, 2011

What is the point of lenses being offered in various diameters? I haven't heard an argument that wider lenses offer superior image quality or superior performance by any other metric, so what's the point? Why not just keep lenses as small and light as possible?

I had theorized that wider lenses let in more light and therefore enable superior low-light photography, but this does not pan out in either of two interpretations:

At a given focal ratio, a wider lens does not offer any more light than a less-wide lens.
Wider lenses also don't generally offer a wider max aperture at any given focal length, which seems incredibly counter-intuitive to me, but that's how it is.

So, what's the point of larger lenses?

Thanks.

--
Personal website: http://keithwiley.com

Kuppenbender · Jul 5, 2011

kebwi said:
Why not just keep lenses as small and light as possible?

They do.

Are you suggesting that lens designers use larger elements in their lens designs for anything other than their intrinsic optical qualities?

kebwi · Jul 5, 2011

Kuppenbender said:
kebwi said:

Why not just keep lenses as small and light as possible?

Click to expand...

They do.

Are you suggesting that lens designers use larger elements in their lens designs for anything other than their intrinsic optical qualities?

To rephrase my original question with greater specificity, there are three popular long-zoom lenses for the Sony a55: the Sony 18-250, the Sigma 15-250 and the Tamron 18-270. I'm curious why the Sony and Tamron are 52mm but the Sigma is 72mm.

Is it totally utterly arbitrary, or is there a reason?

--
Personal website: http://keithwiley.com

nelsonal · Jul 5, 2011

As far as filter ring diameter, one big reason is consistancy means owners of a large number of lenses need to only buy a few copies of expensive specialty filters which can be used with all lenses. Quality polarizers, for example, are expensive so being able to share them across all lenses means you only need one for the group. Also for some lenses this means you'll essentially get some advantages of a hood built in with the lens (as the lens barrel is essentially extended out to fit the "standard" filter ring size).

As far as size, a big factor is large apetures on long lenses mean larger front elements. So to get a max apeture of f/5.6 on a 300 mm lens the front element must be at least 53mm, f/4 would require 75mm. It can be bigger than that but not smaller.

kebwi · Jul 5, 2011

nelsonal said:
As far as filter ring diameter, one big reason is consistancy means owners of a large number of lenses need to only buy a few copies of expensive specialty filters which can

But that's exactly my point! I bought the Sigma lens which is 72mm. Now I'm considering getting a Sony prime lens, and the filters I have won't fit it; I'll have to buy duplicate filters. It is the lack of consistency which lies at the root of my question in this thread.

nelsonal said:
As far as size, a big factor is large apetures on long lenses mean larger front elements. So to get a max apeture of f/5.6 on a 300 mm lens the front element must be at least 53mm, f/4 would require 75mm. It can be bigger than that but not smaller.

Well, I see your point, but if the Tamron goes to 270 and is 52mm then why does the Sigma, at 250, have to be 72mm? One might respond that the Sigma offers a greater aperture, but again, as per my original post in this thread, this is exactly not the case...thus my original question.

I'm sorry, I seem to have phrased my original question in a way which confused the point that underlies it. I apologize for that.

Do you know why the Sigma lens is 72mm but the Sony and Tamron equivalents are 52mm, bearing in mind that the Sigma does not offer greater aperture at any given focal length than the other two lenses?

Thanks.

--
Personal website: http://keithwiley.com

Albino_BlacMan · Jul 5, 2011

Different lens designs require different front elements. Some designs require smaller front elements than others.

Also building lens is all about compromises. No lens is perfect. Some manufactures concentrate on keeping weight down, especially on less expensive lenses. This may have adverse effects such as vignetting when the lens is not stopped down (darkening around the outside of the image especially the corners).

Lens manufacturers may accept a certain amount of this to keep the size weight and price of the lens down (which is probably what is happening on the Sony and Tamron lenses).

Other manufactures may look for better performance and accept a bigger element (probably what Sigma is doing). While their is no direct correlation this is often the case. Also lenses for full frame cameras usually have to have a larger front element and filter size as they have more sensor to cover. Maybe one is made to work on a full frame sensor as well.

As far as filters go. If you use a protection filter first BUY A GOOD QUALITY ONE! I just use B+W F-pro filters. For effects filters such as a polarizing filter, buy one for the largest lens filter size you expect to own. If the largest will be 72mm than get a 72mm polarizing filter. If the largest will be 77mm get one of those. Than, so that you don't have to buy the filters again, buy a step up ring. This is just a ring that allows bigger filters to be used on smaller lenses. For example a 52-72mm step up ring will screw on to the front of your lens that uses a 52mm filter and allow a 72mm filter to be screwed onto the front of the ring. Than you just have to buy step up rings for new lenses.

The largest filter diameter I own and will own is 72mm so I have a 72mm Polarizing filter and a 72mm ND filter and 58-72mm step up ring and a 52-72mm step up ring. The one disadvantage to this is you can't use a bayonet lens hood and a step up ring at the same time
--
Chris

Andy Crowe · Jul 5, 2011

kebwi said:
What is the point of lenses being offered in various diameters? I haven't heard an argument that wider lenses offer superior image quality or superior performance by any other metric, so what's the point? Why not just keep lenses as small and light as possible?

Different designs. A wider front element vignettes less, take the Sigma 50mm f1.4

http://www.dpreview.com/lensreviews/sigma_50_1p4_c16/page2.asp

It's a fair bit wider than other 50mm, and with that extra width has 2/3rd of a stop less falloff.

Dennis · Jul 5, 2011

kebwi said:
Well, I see your point, but if the Tamron goes to 270 and is 52mm then why does the Sigma, at 250, have to be 72mm?

If the Sigma is 72mm for compatibility (and that's speculation), it's for compatibility with other Sigma lenses. They wouldn't care about compatibility with Tamron or Sony lenses.

That said, I don't buy that argument as Sigma's filter threads are all over the map.

However, the older 18-200 was physically 70mm in diameter (with 62m filter thread), while the newer OS model is 79mm diameter (72mm filter thread) so whether the bigger diameter front is required, it seems to at least be based on the size of the lens.

It probably helps avoid vignetting at wide angle settings, too.

Dennis

--
Gallery at http://kingofthebeasts.smugmug.com

Joseph S Wisniewski · Jul 5, 2011

kebwi said:
Kuppenbender said:

kebwi said:

Why not just keep lenses as small and light as possible?

Click to expand...

They do.

Are you suggesting that lens designers use larger elements in their lens designs for anything other than their intrinsic optical qualities?

Click to expand...

To rephrase my original question with greater specificity, there are three popular long-zoom lenses for the Sony a55: the Sony 18-250, the Sigma 15-250 and the Tamron 18-270. I'm curious why the Sony and Tamron are 52mm but the Sigma is 72mm.

Is it totally utterly arbitrary, or is there a reason?

Well, first, the Sony and Tamron are 62mm, not 52mm, so the difference isn't as large as you thought. And, if the Sony prime lens you mention elsewhere in this thread is really 52mm, then you have the same problem, because none of the 18-250 or 270 lenses are 52mm.

The biggest difference is that the Sigma is a stabilized lens. That's one of the things that makes it a bigger beast, 630g, almost 50% heavier than the 440-450g Sony and Tamron.

Now, if the Sigma was actually a 15-something, instead of an 18-something, that would explain the difference, because ultra-wides need larger filter rings. But it isn't.

But still, that brings us to a point of an arbitrary decision on the camera maker, the entrance pupil location. The type, and strength, of the "wide converter" style optics in the lens affect that entrance pupil location. Yes, for a wide, the entrance pupil is only a tiny "hole", just 5mm in diameter on an 18mm f3.5. That's the little "optical hole" that the lens "sees out of". The 18mm lens has to be able to see an 80 degree "cone of light". With a 62mm filter ring, the entrance pupil has to be, at most, 34mm behind the front edge of a mounted filter. A standard polarizer is about 6mm thick, so figure that the entrance pupil can be, at most, 28mm from the front of the lens's filter ring. With a 72mm ring, the lens designer is free to move the entrance pupil back an additional 6mm, leaving more room for optical components that can increase the lens's image quality. Or make it easier to produce. Or both.

But I'm betting that the biggest reason is the stabilization system.

--
Rahon Klavanian 1912-2008.

Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.

Ciao! Joseph

http://www.swissarmyfork.com

Art Jacks · Jul 5, 2011

I have the Nikon 35 f2 af from the dark ages and the Nikon 351.4 G, this is considerably larger than the f2 version, the numbers should tell you why there is a size difference, this example is repeated with my Nikon 85 1.8 af and my Nikon 1.4G, two pairs of the same focal length but different max apertures therefore to allow the extra light transmission to achieve 1.4 the glass needs to be larger. Quality wise I know which of each pair performs the best.
--z

A selection of my images can be found at http://www.photo-genesis.net follow the galleries link then select the Jacks gallery

kebwi · Jul 5, 2011

Joseph S Wisniewski said:
Well, first, the Sony and Tamron are 62mm, not 52mm, so the difference isn't as large as you thought. And, if the Sony prime lens you mention elsewhere in this thread is really 52mm, then you have the same problem, because none of the 18-250 or 270 lenses are 52mm.

Duly noted, thanks. I looked up the Sony 35mm, and it's none of the sizes mentioned so far. It's 55mm......I believe.

Joseph S Wisniewski said:
The biggest difference is that the Sigma is a stabilized lens. That's one of the things that makes it a bigger beast, 630g, almost 50% heavier than the 440-450g Sony and Tamron.

It had crossed my mind that the OS might part of the reason, I wasn't sure.

Thanks.

--
Personal website: http://keithwiley.com

drh681 · Jul 5, 2011

kebwi said:
kebwi said:

Well, first, the Sony and Tamron are 62mm, not 52mm, so the difference isn't as large as you thought. And, if the Sony prime lens you mention elsewhere in this thread is really 52mm, then you have the same problem, because none of the 18-250 or 270 lenses are 52mm.

Click to expand...

Duly noted, thanks. I looked up the Sony 35mm, and it's none of the sizes mentioned so far. It's 55mm......I believe.

kebwi said:

The biggest difference is that the Sigma is a stabilized lens. That's one of the things that makes it a bigger beast, 630g, almost 50% heavier than the 440-450g Sony and Tamron.

Click to expand...

It had crossed my mind that the OS might part of the reason, I wasn't sure.

Thanks.

--
Personal website: http://keithwiley.com

you can get around the multiple filter problem by using filter step up rings.

and to be clear a step-up ring goes from a smaller lens to a bigger filter, a step-down ring goes from a bigger lens to a smaller filter. And no you cant turn one around and use it the other way!

--
Member of The Pet Rock Owners and Breeders Association
Boarding and Training at Reasonable Rates
Photons by the bag.
Gravitons no longer shipped outside US or Canada
-----.....------

if I mock you, it may be well deserved.

klauspauk · Jul 5, 2011

kebwi said:
What is the point of lenses being offered in various diameters? I haven't heard an argument that wider lenses offer superior image quality or superior performance by any other metric, so what's the point? Why not just keep lenses as small and light as possible?

I had theorized that wider lenses let in more light and therefore enable superior low-light photography, but this does not pan out in either of two interpretations:

At a given focal ratio, a wider lens does not offer any more light than a less-wide lens.

Wider lenses also don't generally offer a wider max aperture at any given focal length, which seems incredibly counter-intuitive to me, but that's how it is.

So, what's the point of larger lenses?

Thanks.

--
Personal website: http://keithwiley.com

theswede #100093 · Jul 6, 2011

kebwi said:
At a given focal ratio, a wider lens does not offer any more light than a less-wide lens.

Actually it does, all else being equal (which of course is never the case). This is not seen in aperture, but in vignetting.

kebwi said:
So, what's the point of larger lenses?

Apart from vignetting and standardization, generally simpler construction, which can translate into lower price for assembly and part manufacture (although cost of materials will be higher) and/or higher optical quality. It's a case of diminishing returns as well, or rather of trade-off. A larger lense allows for more leeway, but there will also be more glass to grind and polish. As high quality aspherical elements have become more affordable lenses have generally gone down in size and up in quality, but there are still a lot of tradeoffs involved.

Jesper

scorrpio · Jul 6, 2011

Actually, looking at lenses carefully, one can notice that their bodies are pretty much the same. But the front ring on Sony and Tamron is a bit smaller than the main body - while Sigma's ring is a bit wider. And yes, Sigma is likely to show less vignetting, especially if used with a filter.

Chato · Jul 6, 2011

kebwi said:
nelsonal said:

As far as filter ring diameter, one big reason is consistancy means owners of a large number of lenses need to only buy a few copies of expensive specialty filters which can

Click to expand...

Buy step up rings. Buy the filter that matches your largest lens, and buy step up rings for the smaller lens.

Dave

"Everyone who has ever lived, has lived in Modern Times"

Joseph S Wisniewski · Jul 6, 2011

Chato said:
kebwi said:

nelsonal said:

As far as filter ring diameter, one big reason is consistancy means owners of a large number of lenses need to only buy a few copies of expensive specialty filters which can

Click to expand...

Click to expand...

Buy step up rings. Buy the filter that matches your largest lens, and buy step up rings for the smaller lens.

For the most part, I prefer the "high use" filters, polarizers, 80A, etc. in sizes for each lens, so I can use the manufacturer's "petal" hoods. That, and the whole "remove hood, screw on adapter, screw on filter, screw different hood onto filter" thing gets old after a while. The best filters are the ones you actually use, and I use them more when they're easy. I can change an 80A off a lens without removing the petal hood.

But when I use a step-up or step-down ring, I usually get the good ones. I've had problems with cheap ones, the generic house brands at B&H or Adorama, getting stuck when I wanted them off, yet coming loose when I wanted them on.

The good ones don't have to be expensive (except for 40.5mm-52mm, because only B+W made it at the time I needed it. $35 for a step-up ring. Ouch). The Tiffen branded ones are excellent (or at least were, the last time I bought one. I believe Tiffen's changed hands again) and the Kenko branded ones are good and were only $1 more expensive than the "bower" branded ones that turned out to be such junk.

Chato said:
"Everyone who has ever lived, has lived in Modern Times"

Yes, but only Charlie Chaplain could star in it.

--
Rahon Klavanian 1912-2008.

Armenian genocide survivor, amazing cook, scrabble master, and loving grandmother. You will be missed.

Ciao! Joseph

http://www.swissarmyfork.com

Andrew Houghton · Oct 26, 2021

Firstly, the front element affects the amount of light captured, the circle of confusion, the vignette and therefore the edge sharpness. I’m turn this affects the bokeh or depth of field. The number and type of elements used affect the length of the lens. Larger front elements allow larger sensor sizes to use the lens, the lenses you stated may only be for use with APS-C or 4/3 sensors, vignetting and barrel and pincushion distortion, and edge sharpness may not make a lens with a 52mm front element suitable for full frame.

tbcass · Oct 26, 2021

Andrew Houghton said:
Firstly, the front element affects the amount of light captured, the circle of confusion, the vignette and therefore the edge sharpness. I’m turn this affects the bokeh or depth of field. The number and type of elements used affect the length of the lens. Larger front elements allow larger sensor sizes to use the lens, the lenses you stated may only be for use with APS-C or 4/3 sensors, vignetting and barrel and pincushion distortion, and edge sharpness may not make a lens with a 52mm front element suitable for full frame.

Kebwi, the person you were replying to, hasn't posted anything in over 10 years. As such I doubt he will see your post.

Phil A Martin · Oct 26, 2021

Andrew Houghton said:
Firstly, the front element affects the amount of light captured, the circle of confusion, the vignette and therefore the edge sharpness. I’m turn this affects the bokeh or depth of field. The number and type of elements used affect the length of the lens. Larger front elements allow larger sensor sizes to use the lens, the lenses you stated may only be for use with APS-C or 4/3 sensors, vignetting and barrel and pincushion distortion, and edge sharpness may not make a lens with a 52mm front element suitable for full frame.

Zombie thread, this OP is from 20011.

52mm vs 72mm, why the option?

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