Is my lens broken?

Discussion in 'Canon EOS' started by chrissy_katina, Sep 7, 2011.

  1. Hello! I am new here and having an issue with my Canon EF 50mm 1.8 lens. I have a Canon 7D and I am not sure what is going on. The left side is almost always blurry when I take photos using the 1.8 lens. Does anyone know why this is happening? I really need to figure this out! Thanks!
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  2. HI C.H.
    I would reset your camera to default settings, the same way it came out of the box, without seeing the lens its a guessing thing, and for the moment we will pretend the lens is in perfect working order, I suspect that your focal points, on your 7d is set at center weight or set to focus on one particular point , that is causing the left side of your shot to be blurred, the 7d has many more focal points to choose from than the prior Eos bodies such as 40d or etc, and when you have a large group , as you have shown , the camera picked the spot set up on the camera,and if it is not in auto , where all focal points are being considered ,therefore, your camera is getting only a portion of the subject your shooting in focus, this happens very easy, and is a useful tool when your working with 1 or 2 people but not a large group. So give that a try and let us know ,and hopefully that will have your issues fixed, I have this lens and , it is well know for giving very sharp vivid full photos.
     
  3. The whole photo looks a bit fuzzy on my screen, so I can't see much difference on left side. What f stop are you using? I have the same lens and it has behaved impeccably, although I almost never use it at f1.8.
    It is a very light construction, however, and I suppose a lot can go wrong.
    Maybe you should set up a tripod and photograph a newspaper page at decreasing apertures from f1.8, then check the clarity of centre & corners? good luck
     
  4. Like James, I would never shoot a group like this at f/1.8.
    That said, yes, there seems to be something going on with the left-side of the sample image you posted. If it's a problem with the lens or a problem with technique, that's hard to determine based on this image alone.
     
  5. You have an element alignment issue, the lens needs to go to Canon, but for the cost of the fix it might be better to just get another one. On the flip side if you get your one fixed, at least you will know it will be a good one.
    Having said that, why in gods name are you shooting group portraits at 1/640 and f1.8? f5.6-f8 is where you should have been.
     
  6. I think something's wrong. Check the high resolution version and see if you can trace the region of sharp focus in the grass. To my eyes it appears to be along the subject's toes on the right side and center, but left of center it begins creeping backward, and almost meets the background on the left edge. Of the three white banners or pillars or whatever in the background, the one to the left is significantly sharper - I assume those are all the same distance away?
    In short - it looks to me like you've got a lot of field curvature on the left side - I don't know what causes that, but it isn't normal.
     
  7. Re: the lens choice and using f/1.8, I would assume Chrissy was trying to get a blurred background. f/5.6 would render everything sharp, and I think it would spoil the photo.
    I do have a composition critique though - it's framed too tightly - if the bride asks for an 8x10 you won't be able to print it without cropping out the girls on the ends.
     
  8. Alan,
    What spoiled the photo was that everybody wasn't sharp, even with a good lens using f1.8 is a lottery, to do it for an eleven person group shot is, strange. The blur could have been increased by grouping them differently, moving them closer to the camera and further from the background and still used f3-f4.5, a far safer gamble.
     
  9. Well, I'm seeing a focal plane about 9 or 10 feet tall, shot with a 50mm lens on a 7D implies a quite significant subject-to-camera distance - I'm calculating about 30 feet. Depth-of-field calculator says the DOF at f/1.8 will be 7.5 feet. Sufficient for a group as long as nothing goes wrong. I'd say what spoiled the pic was the curved field.
    I would concede that most wedding photographers probably don't take gambles on shots like this. But I would have - since I don't shoot single-chance kinds of events like weddings, I often work with very narrow DOF. The keeper ratio isn't great, but the keepers are exceptional photos.
     
  10. DOF field calculators have their place, shooting a group wedding portrait on a $100 lens wide open at f1.8 isn't one of them.
    This is an occasion where equipment familiarity really should have taken precedence. Yes I believe there is a problem with the lens, my 16-35 does the same thing but on the right side, ergo, if I use the lens I don't frame with important things there, but why push your luck on somebody's wedding day photos? A 50 f1.8 is never going to be sharp at f1.8.
     
  11. I have an exif viewer plugin running on firefox and it shows that the photo was shot at f1.8
     
  12. I think we all know that Andrew........
     
  13. Several years ago, I had a kit zoom that produced the same results. As Scott says, it was due to a misaligned lens element. In your situation, I don't think I would send this inexpensive lens back to Canon for repair unless it's under warranty. The OOF left side was likely exacerbated by the wide open aperture. Try a few test shots with the aperture stopped down and see if your results are the same.
     
  14. As people have noted, the short answer is yes, your lens has a problem - the plane of focus appears to be quite significantly tilted horizontally, focusing further away on the left hand side. Having shot this at f1.8 has helped you see this, the effect would have been disguised somewhat at smaller apertures.
    I would simply buy another one, the cost of the repair and shipping would probably almost equal the cost of a new lens - also, you could buy a new one today and save the hassle and wait time.
    Regarding your settings, I would only shoot this lens wide open is there were no other option. It's a surprisingly good lens once stopped down a bit, but wide open not so much. As a rule, with this kind of image and depending on the light, I'd be shooting in the f5.6 to f8 range.
     
  15. I think we all know that Andrew........​
    I was clearing it up for the people that mentioned they were unsure if it was shot at f/1.8, while also mentioning a tool they themselves could start using.
     
  16. Time for a new 50, unless it's under warranty, it's not going to be worth fixing. Maybe a nicer one than the 50/1.8... And don't listen to these jerks who want to lambast you for shooting a group shot @ f1.8 -- obviously it worked (except for your lens problem of course ;-) ), and considering that your effective DOF @ f1.8 for that distance was aprox 4.5', that actually gives you a bit of comfort at the edges (though obv. not much)... I'm sure some jerkwad will continue to roast you about it though (*rolling eyes*)
    Congratulations on getting it done when some of these guys are too scared to even try it! Don't be afraid to keep trying risky stuff -- It's the best thing about digital...
     
  17. Thanks Marcus,
    I suppose it depends entirely on the personal opinion of what you think worked and how good you think the edges of a $100 50 f1.8 stand up to the application of the DOF tables, and, what kind of product quality you want to sell. If I was using a Holga I would consider the image a success. If I was the bride and was expecting sharp images, not so.
    Never be afraid to try new stuff, but if it is somebody's wedding day only do it if you have a known shot in the bag. However, again, " A 50 f1.8 is never going to be sharp at f1.8."
     
  18. IDK Scott, if that shot were taken @ f4+ as suggested, it would be vastly worse, the trees, while OOF would be sharp enough to distract the eyes, nevermind the pillars (?) which are already distracting enough... Of course that's a personal observation, and why I like fast and superfast lenses. And while I'd never expect 'optimal' performance from any lens WO, the 50/1.8 remains decent even WO (unlike, for example the EF 50/1.4). I think you may be confusing 'optimal' with useable -- the bride in the pic IS critically sharp (at least from what I can see in a downrezzed version) @ f1.8. This matches my experience with the lens (one of the reasons 'upgrading' to the 50/1.4 was so disappointing) -- so, while not 'optimal' @f1.8 the 50/1.8, is definitely very useable.
    The bottom line is that the flaw the OP asked about is not related to the criticisms posted, sure stopping it down considerably may help hide that flaw, but the problem will persist noticeably in the affected region at the vast majority of useable f stops. I've had one lens do that, and it is unfortunately the death knell for a cheap lens.
     
  19. If you can run a test case that eliminate as many variations as possible you can probably be pretty certain whether it is a lens issue or not.
    I'd shoot at a nice mid-range aperture like perhaps f/8, use MLU or live view, use a remote release, and make sure that the subject is exactly parallel to the sensor plane. If you still have the soft left side at a fairly conservative aperture, there probably is an issue somewhere that will require service, On additional thing you might do is try another lens - your own, borrowed, or even rented - to see if the same issue occurs.
    My hunch is that it is a lens issue involving alignment of the lens elements. I have had this happen in the past to lenses of mine that received reasonable but not super-gentle treatment, and a trip to Canon straightened things out nicely. However, these were much more expensive lenses, and the repair cost was only a fraction of the value of the lens. The story is different with the very inexpensive EF 50mm f/1.8. The repair would cost more than a new lens!
    There are other possible issues besides a problem with alignment of elements. You could have some alignment issue with the lens mount or with the base of the lens itself. I can imagine that some issue with sensor alignment could even be at play given the very tiny errors that will cause a problem. (Here, too, checking with a second lens could help.)
    If you do end up replacing the lens and if you intend to do much of this sort of shooting, look into something a bit more solid than that f1.8 prime perhaps. The f/1.4 could be a better bet. And don't shoot either wide open unless you really have to do that. At a minimum this creates some DOF issues with subjects that are not in a perfect plane. It also generally diminishes resolution a bit and makes perfect focus even more critical. And if you are going for a OOF background, you can also get the by being a bit closer to the subjects, and putting a bit more distance between them and the background, the less busy the background the better.
    Dan
     
  20. I have uncovered your query after buying a used lens (16-35) Canon and finding the right side blurry on a 5Dmk3. It is the lens since other lenses do not have this problem. I did do a quick tweak on your photo however and corrected some of the problems. If it were my photo I would work on it more but the most valuable aspect of the exercise is that by correcting the problems with the photo you learn what to avoid in composing[​IMG] your next interesting shot; whether that be an impromptu wildlife or landscape or a person. Bright direct sunlight is nearly impossible to include with darker areas; you're now well aware of depth of field focal plane issues, the benefits of using reflected light or a flash for fill.
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