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05/16/2011 09:46:18 AM · #1 |
My 50mm 1.8 lens.
So I have been using my 50mm quite a bit lately for portrait work and some still life and florals. I have noticed it is really hard to get a good sharp focus even if I have the aperture at say 7. And trying to do any sort of work with the aperture wide open at 1.8 is impossible. The focus is never where I think it is going to be or even there at all. I use a tripod, and focus my little red dot on a certain subject like a small flower and then I am disappointed to see an almost entirely out of focus image. You would think the focus would land somewhere, even if it was just on a really small area.
I had a photo shoot with my little dance girls and decided to just use my 18-55mm lens, so that I can zoom in and out as needed. I was much more impressed with the focus, especially on the full body length images.
Is there something I am doing wrong or do others have this problem? I thought the 50mm was especially designed for portrait work. I also must mention I dropped it when I first got it, but was able to repair it and it seems to function just fine. |
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05/16/2011 09:55:48 AM · #2 |
50mm lenses were not "designed" for portrait work. The 50mm focal length was originally considered the "normal" lens in that it had an angle of view similar to the human eye on the 35mm format. With the APS-C sensor size in your camera it is more like an 80mm lens by comparison. 80mm is a fine focal length for portraits.
Your particular lens, while a decent performer optically, is made very cheaply to keep the price very low. It is actually an excellent value for the quality of images it can produce. However, dropping it will expose its frailties. It is not a lens that can take a lot of physical abuse.
My guess is it suffered more than you think from the drop. Seeing as the price of the lens is <$100.00 in most cases, it will probably be less costly to replace it than to get it repaired.
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05/16/2011 09:57:45 AM · #3 |
| Are you using auto- or manual-focus? If the latter, try changing the diopter adjustment on the viewfinder to see if it is a little off. If you are using a tripod, try turning off image-stabilization (if it's on now). |
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05/16/2011 10:07:23 AM · #4 |
| I'd suggest doing some quick tests to see if the lens is consistently back or front focusing. If you can identify a consistent focus problem then you may be able to make a focus adjustment in your camera's menu which will compensate. Most current model DSLRs offer this function. Someone else more familiar with Canon may be able to confirm if your camera offers this. Also, don't forget that at f/1.8 you are dealing with a shallow DOF, so it can be easy to miss focus a little if the camera or subject move slightly relatively to one another. However, this doesn't explain your problems at smaller apertures. Hope this helps. |
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05/16/2011 10:08:27 AM · #5 |
You may very well have a focus issue with the lens. Try doing some focus tests with the lens, using wide but not insanely wide apertures, say f/2.8 or f/4. Try to figure out whether the lens is always focusing in back or in front of the subject or if it is just unpredictable. Try manually focusing and see if you can obtain sharp photos.
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05/17/2011 08:56:31 AM · #6 |
Best guess is that the dropping affected it more than you thought - or it was duff to start with. Construction is the nifty-fifty's achilles heel.
You can't turn off the IS - it doesn't have any, and on the 400D you can't do micro-focus adjustments sadly, so those options are gone.
Perhaps try having someone else take manually focussed shots with it, which will help show if it is a diopter problem? Still, if you are having the same issues when using AF, I suspect that it is just a bit broken. :o( |
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05/17/2011 09:28:37 AM · #7 |
Thanks guys, it still works well for close ups on portraits. I think I will still use it for that and if I don't use too small of an aperture I can get it to work for still life. I am just going to have to switch to my other lens for full body work and family portraits. Which probably means I won't switch at all.
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05/17/2011 09:31:00 AM · #8 |
Some technical considerations:
1. Minimum focusing distance is 0.45m (1.5 ft.). Get closer than that and the image will be oof, regardless of how it looks in the viewfinder.
2. At the minimum focusing distance of 1.5', with aperture wide open at f/1.8, your total depth of field plane is going to be a sliver at 0.02 ft. (6 mm.) So, wherever your single focus point locks on, there will be 3mm behind and 3mm in front in focus. If you are using more than one focus point, your camera may be doing its job, but not as you intended.
3. There is the issue of shutter slap, mirror slap or other vibrations slap. This usually happens at very low shutter speeds, like 1/4s. The fix is to try your mirror lock up function. Mostly applicable for macro photography.
4. Imparting muscle vibrations to the camera can cause camera shake. If your finger is on the shutter release button, no matter how gently you pull the trigger, you can impart muscle vibrations to the system. This can result in reduced sharpness. The solution is to use the (1/lens focal length) for shutter speed, (or faster) rule of thumb. 50mm x 1.6 = 1/80s or faster to mitigate touching the camera, even if mounted on a tripod. A good solution is to use a remote shutter release (cable or wireless). If that doesn't help, then refer to items above.
Don't know if any of these are a source of oof-ness. But, these are things I've tried in the past to observe better results. |
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05/17/2011 03:22:27 PM · #9 |
| you aren't setting an AF point and recomposing are you? |
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