More and more I see questions getting closed, or getting a lot of closed votes, when in my mind they are not exact duplicates. I'd like to avoid specific examples here, more interested in general philosophy rather than arguing about specific questions.

In my mind, an exact duplicate is just that. Not the exact wording of course, but the same question where the same answer applies. Not a similar question, or a subset of another question but effectively the same question. One that could easily be found by a search of the site and immediately recognized as duplicate.

As Jeff says

One thing I want to be clear about, though, is that duplication is not necessarily bad. Quite the contrary — some duplication is desirable. There’s often benefit to having multiple subtle variants of a question around, as people tend to ask and search using completely different words, and the better our coverage, the better odds people can find the answer they’re looking for. And isn’t that, really, the whole point of this exercise?

Furthermore, it’s OK for duplicate questions to have duplicate answers. While you could argue that the duplicate questions could all be merged into one question with a “master” set of answers, this is kind of irritating from the perspective of the user looking for an answer. Put yourself in their shoes. Instead of finding

Duplicate Question — Duplicate Answer

They have to deal with finding:

Duplicate Question — [closed as duplicate of Question] click here to see answers

"subtle variants of a question" doesn't sound like what we allow here - we seem to me to do is look for the slightest connection with another answer and flag it as "possible duplicate".

There are a few types of questions I often see getting a lot of close votes here lately:

Simple question (with a simple answer) where there is a more general question with longer, involved answers

Sure, the long involved answers will provide enough information, if absorbed, to answer the simple question, but that doesn't make them a duplicate. We should in fact encourage simple questions with simple answers. A recent example was someone asking if shutter speed and film speed were the same thing, related, or independent of each other. That got a lot of close votes as a duplicate of the epic "what is the exposure triangle" question. No one should have to try to read 16 paragraphs of information to get what is effectively a yes/no answer to a simple question.

As Joel says:

For example, if a user asks, “What does the IP address mean?” it’s OK to close that as a duplicate of a more general question like “What do IP addresses of the form a.b.c.d/e mean?” But it’s not OK to close it as a duplicate of a twenty-seven page guide to netmasks. That’s the moral equivalent of saying “RTFM.”

So again, just because another answer (to a different question!) does include the answer to a simpler question, being a superset of the needed answer doesn't make it a duplicate.

Simple questions where there is a similar question

These are hard, and I know it's a gray area. But to me, most of these types of questions are often not duplicates, but are often flagged as such:

  • Compare lens A vs lens B (Canon) where there is already a Nikon question on the equivalent lenses. There are distinct differences between specific lenses of different manufacturers. The Canon 50mm 1.4 may have horribly slow AF, and the Nikon soft in the corners. Sure there are general principles if they're comparing a prime lens vs kit zoom, but the offerings do differ between brands, and if they are asking a specific question about Canon, I don't feel we have the right to force them to generalize their question if it's Canon they want information on.

  • "Compare lens A vs lens B", where there is already a "Compare lens A vs lens C". No comment, but this happens a lot. Should we allow every conceivable combination of lens shopping questions? No comment there either. But A vs B is clearly not A vs C.

  • "Is f/4 lens with IS or f/2.8 lens better for sports?" when there is an existing question "Is ... or ... better for travel?" (or wildlife or portraits...). Surely not a duplicate, as different genres of photography have different requirements. And this allows people who are more experienced in wildlife or portraits to write specific answers for those genres. Trying to lump everything together is I think the opposite of what we should be doing. If I search on Canon 70-200mm f/2.8 and see a number of questions about various genres, and comparing it to a variety of other lenses, I'd rather see all those questions and read through them, rather than have one general question which doesn't really address the specific angle I was after

Jeff again:

There are similar questions, yes, and so-called “exact” duplicates do happen, but they are kind of rare in my experience. It’s far more common to have many subtle variations of a question.

"Subtle variations" again. So are we sometimes being overzealous about closing questions? I think so. I think it discourages new people having their questions closed, and I think having a smaller set of questions discourages people from adding more answers if there are already 6 answers, one accepted. If a new question allowed, with a slightly different slant, it gives other people the chance to add their experience, where it is more relevant than on the more general "duplicate".

Questions where a poorly worded question already exists

Here we can edit the original question to make it better but I think we should simply allow a new, better question.

I think we should use a higher bar for determining a question is a duplicate. And I think if you find a related question, it's valuable to add that in a comment, but mark it as "related" rather than "possible duplicate".

  • possible duplicate - meta.stackexchange.com/questions/38375/…
    – MikeW Mod
    Apr 9, 2013 at 20:48
  • 3
    We do have a tendency to shut down on "similar" here, but I think you're making a good case that we should ease up on that a bit.
    – Joanne C
    Apr 9, 2013 at 22:55
  • 1
    I found PhotoSE less than six weeks ago, so a very new user. Even so, I've noticed it too. The first comment to a new question is so very often starting with words "possible duplicate.." and of course the link that follows is often helpful, but the closing of the said question as duplicate often is not so helpful. Apr 9, 2013 at 23:44
  • 1
    One thing I've noticed: the close votes review system seems to include questions where there isn't an actual vote to mark as duplicate, just another question mentioned in a comment. This can have the effect of escalating comments like "This other question has some related info..." into close votes. Presumably this is by design.
    – mattdm
    Apr 10, 2013 at 11:32
  • Aha. That may explain a lot then. It seems a lot come up for close votes that don't seem necessary.
    – MikeW Mod
    Apr 10, 2013 at 11:46
  • Just an example (which you wanted to avoid) of someone's hurry to make the first comment starting with words "possible duplicate". Question about 18% grey and I think the "possible duplicate" is not even near the other one. (Ok, the 18% grey is mentioned..) Why is it so important to get first comment out with words "possible duplicate"? No reputation granted for those comments, so why the rush? Apr 12, 2013 at 6:58
  • To be fair, that question is really two questions. The second part is how to make your own grey card (in PS) and the linked question is on that exact topic. Chills is a mod, so he maybe didn't want to close as duplicate, but just point out that it's partially covered. I don't know if he's literally typed that comment in, or flagged it, still not entirely sure how that all works.
    – MikeW Mod
    Apr 12, 2013 at 8:50
  • Also, I think that the quotes on one side of what Jeff Atwood is saying in your post above totally remove what he's saying from the context. He also says "Let me be clear — too much question duplication is bad. Absolutely. You’ll get no argument whatsoever from me on that."
    – mattdm
    Apr 14, 2013 at 2:22
  • 1
    Well, to be fair, we're not likely to give _any_ room to duplication, so we may swing to the extreme on the other direction. At any rate, this has been one of the more valuable discussions on Meta that I've seen, so I'm quite happy.
    – Joanne C
    Apr 14, 2013 at 2:30

4 Answers 4


Another case: confused questions which ask several different things at once, most or all of which are already answered.

Often this attracts replies which cover one aspect. Or, it attracts big omnibus answers which are hard to vote on (because they may cover one aspect better or worse). The end result is a Q/A which just clutters the site. Future visitors who wonder about some portion of the question end up with a lot to wade through. Basically this is the failure of bb-style discussion forums for Q&A, brought here.

I have been voting to close these as duplicates of the primary question and adding links to other questions. But I guess I could also be convinced that Not A Real Question, Too Localized, or Not Constructive would be better, maybe often with a suggestion that Chat is a good place to take a wide range of topics.

  • 2
    Yes, or have them split it into 3 questions, then close each of those as duplicates :)
    – MikeW Mod
    Apr 13, 2013 at 21:57
  • In today's example, the linked question is almost 3 years old. At some point, I think it's good to let new questions come to the fore again. The points from Jeff Attwood fit this one almost to a T and, even better, has resulted in an answer that ties a lot of things together.
    – Joanne C
    Apr 14, 2013 at 1:07
  • To me, a primary reason this site is better than a traditional web forum is that older posts can stay relevant, useful, and updated. Sure, sometimes things get so out of date that it's better to start afresh, but overall I think we should strive for lasting knowledge.
    – mattdm
    Apr 14, 2013 at 2:20
  • 2
    The age, though, is bound to effect how people view it. 3 years is an eternity on the Internet and pretty close to that for technology in general. Also, we have a very high rate of duplicate, I think, and that either means we're of limited long-term value or we're just a little too aggressive on what a duplicate is. I think it's the latter. If there's a sniff of it being the same, we shut it down and I've been as guilty of that as any. I just think we should reconsider that a bit.
    – Joanne C
    Apr 14, 2013 at 2:27

Let's take today's version of the lens question as an example, shall we? It boiled down to "I'm shooting things that move, and I'll be hand-holding, so is f/2.8 with IS better, or f/1.4 without?" Brand and focal length don't matter in the slightest, nor does the lensmaker's image stabilization efficiency. If f/2.8 can take the right picture at all, then f/1.4 is the wrong aperture; the lens's extra speed is moot. It's even less of a concern if you need to shoot at f/5.6 for adequate depth of field. And IS of any description won't make up for subject motion. All of this has been covered before (more than once), even if it didn't specifically mention Canon-brand 24mm lenses. And it really doesn't matter that the asker didn't want to hear any fundamental and inescapable truths.

At some point, we need to require people to make some inferences. What applies to lenses mounted on a Nikon often also apply to Canon, Pentax, Sony, Olympus and Hasselblad, for that matter. And yes, it is okay to edit both questions and answers to cover the general case when the specific is ridiculously specific (such as being brand-specific when the principles apply globally). There are already far too many "gear" questions on the site (probably because we're mostly tech-heads who've drifted in from other stacks and can't help ourselves), and I'd have no problem at all with a Great Purge (or at least a Great Merge). And maybe we can make the site about photography instead of about cameras.

  • 1
    I'm with you on the gear (and a bunch of those "what is this effect" for the same effect questions), but there is a tendency towards some assumptions that I think newbies to photography aren't really going to get. It's a fine line I suppose.
    – Joanne C
    Apr 10, 2013 at 0:20
  • 1
    all not-tech-heads, raise your hand! _o/ here as an example of one that did not drift in from another stack and who is interested in psychology and human behaviour in general. Apr 10, 2013 at 0:22
  • You are referring to this question, and I completely agree. It is a generic question that mentions Canon, but is completely generic.
    – MikeW Mod
    Apr 10, 2013 at 0:23
  • What triggered my question was this where there is much more to the question that lens A vs lens B, because a) brand may matter and more importantly b) there are future lens purchases that may affect the initial lens purchase.
    – MikeW Mod
    Apr 10, 2013 at 0:26
  • I don't know of too many people (besides myself) who would be content with a 50mm/1.8 as their only lens, @MikeW. But the principles still generalize across brands.
    – user2719
    Apr 10, 2013 at 0:33
  • @EsaPaulasto -- if it's any consolation, I wound up in tech after losing my shirt (and several shirts I'd borrowed as well) as a pro photographer and ruining a perfectly good hobby (which I initially got into to collect references for painting). Never, ever set up a studio at the beginning of a major recession in a city that's about to lose all of its regional corporate headquarters. And if you have to do that, try not to buy any gear that's obsolete in two weeks. (Being an earlier digital prepress adopter in Halifax in the early '90s was, in retrospect, a mistake.)
    – user2719
    Apr 10, 2013 at 0:40
  • Great to have a painter in PhotoSE. Do we have a GTKY tag that I just saw mentioned in another Stack? oh but why I ask, I'll just go to main and search for it. Cya. Apr 10, 2013 at 1:19
  • Meh. There is nothing magical about either Canon or Nikon's slower 50mm or their kit lens. I stand by the statement (and the quest asker agrees) that the earlier question covers it.
    – mattdm
    Apr 10, 2013 at 2:24
  • On that second question that @MikeW listed, why shouldn't it be closed and merged? The original question could be updated to reflect a more generic question that isn't so brand specific.
    – Joanne C
    Apr 10, 2013 at 2:54
  • JoanneC: There is a more generic one - httpa://photo.stackexchange.com/questions/16404/whats-the-advantage-of-buying-a-fixed-50mm-f-1-8-lens-when-my-camera-has-an-18 - the Nikon one has answers specific to the Nikon lens, while the answers to the most recent question are specific to Canon (e.g. the 50mm 1.8 as very slow AF). The Q askers also have different criteria: one says he'll mainly shoot portrait, nothing moving fast, low budget, no stated intention to buy any other lenses in the near future
    – MikeW Mod
    Apr 10, 2013 at 3:39
  • The other states the intention to buy either an 18-135 or a 55-250. Obviously 18-135 is less sensible if he's chosen the 18-55. All the answers talk to the secondary choices of 18-135 or 55-250. Is that too localized? Yeah probably, but far from a duplicate.
    – MikeW Mod
    Apr 10, 2013 at 3:40
  • 1
    Which is why I really didn't want to get on a tangent about a specific question. We could argue each of these all day. Just pointing out that the intention of SE sites it to allow for duplicates, and let's not stretch things too far to avoid duplicates. If you think you have to alter another question to make it more generic so it fits with another question, then it's simply not a duplicate IMO
    – MikeW Mod
    Apr 10, 2013 at 3:42
  • Speaking of tangents into specific questions :) I also agree that the exposure one shouldn't be closed as a duplicate of the exposure triangle thread, but I think largely because I hijacked that one with my terminology agenda. I don't think it would hurt to have a new "What are the main camera settings which control exposure?" question where the terminology/pedagogical argument would be left aside. Then, some exposure questions might still be duplicates of that, or at least "read this first and if that doesn't clear it up...."
    – mattdm
    Apr 10, 2013 at 14:49

I think that it's important to consider the generalized question when considering if something is a duplicate. Taking the typical Lens A vs Lens B scenario. Often it is something like Aperture vs IS in which case that is a general answer to a generalized question of IS vs Aperture and brand and even lens specific details don't matter if it is just that simple.

On a slightly more complex version of the same question however, there may be a reason why something specific to that particular lens or combination of lenses can't be quantified in a generally correct way. In this case, the question would not be a duplicate since the question can not be further generalized and thus a general answer is insufficient to answer it fully.

It's a tricky judgement call to make and I tend to avoid voting to close a question unless I know the answer well enough to be certain that it is in fact a duplicate. If not, we can always come back around to it after someone who does know the answer about the particular situation chimes in and if it is in fact generalizable, we can always close as duplicate at that point.

Perhaps the other thing we should try to do when we see this happening is to revisit the previous question and try to pull out the generalized question as opposed to an apparently equipment specific question that may be less obviously the answer. This would also (hopefully) reduce the number of duplicates asked in the first place.


I think there are three common cases of duplicates.

The first is the case where we already really do have awesome content on the question being asked. It's often the case that the new question is a straight-up duplicate, or even if the questions might not be identical, it's often the case that one of the other answers actually completely nails it. I don't think the automatic "possible duplicate" comment wording is as nice as it should be, but overall I think the process actually works pretty well here. We don't have a problem with moderators aggressively closing a question, so it actually takes a little bit of time, during which the question-asker can take a look at the information and see if it is helpful, and if not edit the question to better reflect the difference.

The second is basically "what focal length should I use..." lens recommendations. This maybe is a subset of the first, but here, we get the same question for different brands and even for different models, even though really the principles are the same. In this case, I feel pretty strongly that we're not really helping people by encouraging an illusion that there's a big brand difference in, for example, a cheap 50mm vs. the kit lens for baby photos.

And finally, there's the never ending stream of "Zoom lens A vs Zoom Lens B". Here, there really is a brand difference, and a price level difference, and a use-case difference. The worst case of these is when someone is in the grip of decision paralysis and has a list of half a dozen candidates with pros and cons for each and wants us to make a decision; these are probably best just closed as not constructive. But let's it's the more straightforward case of this 70-200mm vs that one. There are still a huge number of combinations, and I don't think exploring every possible permutation is really in the spirit of "multiple subtle variants" referred to above. That makes sense for people trying to understand crop factor, focal length, and sensor size; or even this recent think about how digital sensor ISO works. It makes even more sense when the question is about composition or style. For this, the Canon EF 70-200mm f/2.8L IS II USM is going to be the same no matter which other contender is in the list. So, I'd rather have one per-brand answer for different ranges of lenses where the answer is comprehensive. I tried to do that for Pentax primes at Which prime lens for Pentax APS-C?. This is a long answer, but it's not a case of "simple question (with a simple answer) where there is a more general question with longer, involved answers", because the A vs. B question isn't really "simple" — it's just phrased in an over-simplistic way.

  • 1
    Perhaps some of us could write blog posts that we can reference? A buyer's guide of sorts?
    – MikeW Mod
    Apr 11, 2013 at 1:36
  • There should be buyer's guides around the internet, then why is it that people don't find those, or why they don't trust those? They want to ask for advice from the site that looks to be the most reliable, trustworthy and no-nonsense place they can find. PhotoSE comes up in Google and it looks just the right place. That's what draws in the questions. Apr 13, 2013 at 15:49
  • @esa That, and they just want to be told what to buy without having to think.
    – mattdm
    Apr 13, 2013 at 15:57

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