There is a thread on the Computer Related Help & Discussion forum on the subject of shutter count, the camera in question is a Canon but that is irrelevant since all true shutters are mechanical devices (electronic shutters aren't but electronically controlled shutters are). Given that mechanical devices wear it is important to have some measure of how far between new and worn out they might be. In aviation we measure life in terms of "number of operations" or Cycles, as it is easier to type cycles than shutter actuations that is what I will use. So why does a shutter's cycle count matter? Two reasons; A shutter that has a high cycle count, especially in a relatively young body may be less reliable than a newer one and this will also reflect the level of wear on other mechanical parts, mirror hinge, damper etc. This is of more use to the manufacturer when servicing the camera than to a prospective buyer. A high shutter count may also indicate the type of use to which a camera has been put, my D2Xs had around 90,000 cycles when I bought it and it was cosmetically a bit tatty. That didn't put me off because, the shutter was well below the level to which Nikon had tested, I wasn't going to use it particularly hard, the cosmetics were fixable (£25 or so I recall). Contrary to popular belief, many cameras have the shutter count in the metadata of each image so, with the right software, it is readily accessible. Manufacturers guarantee their shutters don't they? Well actually they don't. What they do is tell you, in their advertising, how many cycles they tested them to, that isn't a guarantee of how long they will last. Others have suggested that this is a measure of MTBF (Mean Time Between Failures). It isn't that either. When a manufacturer designs a new shutter a number of prototypes will be made and tested to iron out any bugs. Then a few hundred preproduction examples will be made and tested to, amongst other things, see how and where, they wear. Some may even be tested to failure but others will be dismantled at 10,000, 50,000, 100,000 and 200,000 cycles so that the wear can be measured. Only after much testing will production start. Some production examples will be extensively tested. Nikon tested the D2 shutter to 250,000* cycles (probably several of them) and then had the confidence to tell their prospective customers. All this means is that they know how the shutter wears over 250,000 cycles and are confident of being able to maintain it. At this stage they haven't sold a single camera so they can't possibly know the MTBF, even the data they have will be misleading because their test units won't have been, in most cases, production examples. The only way to gather useful MTBF data is to sell cameras and repair them. Manufacturers try to design for an acceptable MTBF (which is propitiatory data and they won't release it) and we will never know if their production examples meet that or not. The vast majority of cameras sold to amateurs won't get near their test cycle values or the design MTBF but some professional photographers may approach or even exceed those numbers. What does shutter count mean when I buy used In most cases it is irrelevant. However, if you are buying a "Professional" camera (Nikon D1, D2, D3, D4, D5, D700, D800, D810, D850 etc. Canon EOS1D or EOS1Ds, 5D etc. any mark) a heavily used camera may not be the bargain it looks. A low price may mean a well used example, here the shutter count will be useful. Not that a high cycle camera need always be avoided, see my D2Xs example above, but if you are completely ignorant of the cycles you are taking a greater risk. Also be aware that a cosmetically worn camera with low cycles may have had a replacement shutter. A disclaimer I know that there are members here who know a lot more than I do but this isn't a professional appraisal it is a note on shutter cycle count and why it might matter. If you think it is meaningless that's fine by me. If you feel more confident as to what an advertiser is offering that's fine too. *Why only 250,000 cycles? Good question but they probably expect a new model to be released before too many professionals reach that number. Nikon, and I suspect Canon, expect professionals will upgrade regularly. Consumers just don't use their cameras that hard.