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It is well known that different lenses often have different filter thread sizes.

Why is this the case? Lens and camera manufacturers have agreed on one (per-brand) standard for attaching the lens to the camera, although the appearance of mirrorless has caused some divergence in the attachment standard. However, there are valid reasons for mirrorless lenses having a different lens mount. I don't see any valid reason for having different filter thread diameters.

It seems to me if the lens diameter at one end is standardized, it could be standardized for most cases in the other end as well. Lenses with smaller filter thread size could very well use a larger filter thread size instead.

The exception to this obviously is lenses that are huge. It doesn't make sense to make the end of every lens huge, so it may be the case that perhaps two or three filter thread diameters would be enough. The smallest filter threads in use currently could be replaced with larger ones.

For example, the Canon 50mm f/1.8 lens could very well use 58mm filter thread to match that of the Canon 85mm f/1.8. Currently the 50mm f/1.8 is using 49mm filter thread.

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    "Lens and camera manufacturers have agreed on one (per-brand) standard for attaching the lens to the camera..." Oh? What is that standard? – scottbb Mar 10 at 12:52
  • I often wonder why someone asks a particular question. What is your real motivation? Are you simply trying to buy fewer filters, that share compatibility across a wider range of the lenses you personally own? Do you know about step-up adapters? Could that be a solution for you? – osullic Mar 10 at 14:28
  • @osullic I'm somewhat annoyed by Canon 50mm f/1.8 using a different thread (49mm) than Canon 18-55mm, 55-250mm and 85mm (which use 58mm). It looks like the only reason for the 49mm filter thread is that they wanted to put the text "CANON EF LENS 50mm 1:1.8 STM" on a particular location. – juhist Mar 10 at 16:24
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    If you’re buying lenses because of filter sizes, I don’t understand why you don’t go with the 50mm f/1.4, which matches your 58mm filter – Hueco Mar 10 at 17:25
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    As to your question, where would you stop? The 16-35 f/2.8 has an 82mm filter size...why not completely screw the small and light design of the nifty fifty by essentially doubling it’s barrel size to accommodate 82mm threads? – Hueco Mar 10 at 17:29
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Having a fixed size for the front element is a much bigger design constraint than the size of the "throat" of the lens mount. By locking the entire lens lineup to such a standard, camera system makers would be leaving possibilities on the table — they'd have to decide if they want bulky lenses or small ones. Manufacturers who choose small couldn't make fast lenses with extreme optical correction, and probably would leave wide angle and far telephoto options out completely. A larger standard diameter might mean only heavy expensive lenses ­— or at least it would leave big empty cylinders with a lot of pointless plastic.

But, actually, lens system designers do pay attention to this. For example, all of Pentax's DA Limited lenses (and several of the FA Limited ones) use Ø49mm. Fujifilm's 23mm f/1.4, 56mm f/1.2, and 90mm f/2.0 all use Ø62mm — while the more compact 23mm f/2 and 35mm f/2 use Ø43mm. You could build a very nice, complete lineup of Canon lenses sticking to Ø58mm (or Ø77mm).

You say:

It doesn't make sense to make the end of every lens huge, so it may be the case that perhaps two or three filter thread diameters would be enough.

and, eh, it's more like four or five than two or three — but this is really basically already the case. In every system, there tend to be a few "go to" filter sizes.

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Would you really like to have a 82mm filter thread on your 50mm f/1.8?

Manufacturers tend to not oversize their products. They would not, for example, put the 50mm f/1.8 in the case of a 70-200 f/2.8 lens. It is cheaper to use the smallest casing available - and most customers will like that, too. If you made the 50mm f/1.8 larger (and thus heavier) but optically the same as its predecessor, then marketing would have a hard time to explain that, as most people do not buy lenses based on the filter sizes they already own.


If you want one filter size, go for filter glasses and filter holders like those from Lee Filters. Or use step-up-rings and buy one filter in the largest size you need.

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Lenses have different optical designs, and different maximum apertures. That means that the front elements have different sizes. So if you want all lenses to have the same filter threads you're going to need to pick the largest front-element that is plausible and make all lenses either have barrels that big or have a step-up at the front, which is going to suck for people who like smaller lenses (a lens which has a step-up is, for most purposes, the same size as one which has the same barrel width for its entire length, although it can be lighter): for instance if someone designs a small, light, pocketable camera it's going to be stuck with some giant lens on the front of it and thus not be pocketable at all. And since, unlike with mounts, there's no requirement for compatibility, so long as you pick one of the set of standard threads (there have been lenses with nonstandard threads!), people don't do this.

As an example I use a 50mm f/2 which has a 39mm filter thread and a 40mm f/1.4 with a 43mm: I really would not want either of those lenses to be bigger.

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In addition to what was already answered:
If you are in the business of selling filters, would you rather sell one or multiple filters to every photographer?

[Hint: businesses try to make money]

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    This might make sense ("follow the money" is usually good advice), but do large-brand camera system makers make significant money from filters? In my experience, they are largely a third-party concern. – mattdm Mar 10 at 22:39
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This is more of a complimentary comment on the other answers.

Some types of lenses actually do have the same thread size. For example cinema lenses:

http://rokinon.com/xeen/xeen-cine-system

The reason is that the accessories that go in front of a cinema camera are pretty expensive, so having only one thread size and overall size is an advantage... but people normally do not use filters at all because they want to squeeze most of the lens and then avoid the extra glass.

  • Not all cinema lenses have the same diameter, however: Angenieux has 114mm and 136mm (most are 114mm, though), Canon offers both of them, too (with more 136mm lenses). – flolilo Mar 11 at 11:29

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