EF-S 18-55 Sharpness at Long Exposures

[cole_anetsberger]

<p>Hey everyone,<br>

I don't shoot much in digital, but I went to do some long exposures in moonlight tonight with my XTI and kit lens. Out of the seven photos I took, only one came out reasonably sharp. The exposures were around 5 minutes at f/8 or f/11, iso 200 on a tripod. I used the remote release for the shutter. I am pretty sure my focus was fine (they were mostly landscapes shot at infinity). However, I'm relatively inexperienced at making very long exposures. <br>

Question: does anyone know if this lens just completely sucks for low light long exposures due to it being cheap and having a lot of diffraction or is there something I'm doing wrong? I am thinking a higher quality lens would definitely make a difference but any tips/insight would be appreciated!<br>

-Cole Anetsberger</p>

[nhut-nguyen]

I don't think it's diffraction at f/8 or f/11 or anything to do with long exposure. You say you did it for over 5 minutes, that's really long, a small movement or vibration of the camera/tripod could cause the image to be soft. If you do it outside, wind can be a factor.

[neill_farmer2]

<p>I have an XTi and use it, mostly with a 50mm 1.8, for low light exposures, around 10-15 seconds, f5.6. This camera is very difficult to focus under such conditions, I have found the AF is generally inaccurate and I have to resort to manual focus. I find it takes me around 30 seconds or so to do this accurately. I set the camera on Av, shutter triggered by time delay and I use a medium weight stable tripod (not a flimsy el cheapo). Photos come out very sharp. I have a 18-55 kit lens but have replaced it with a Tamron 17-50 2.8, the kit was just not sharp enough for me.<br>

In short there are two possible causes for your fuzzy shots, camera movement and focus. This type of photography is realy stretching the capabilities of the XTi and its kin, really need to go one step up to the xxD series with its better AF and better viewfinder, plus a lens with more light gathering power (as pointed out to me here when I made comments on the troubles I had getting my low light shots).<br>

Neill</p>

[rainer_t]

<p>-- "I am pretty sure my focus was fine (they were mostly landscapes shot at infinity)"</p>

<p>How did you set the lens to infinity, and what did you do to make sure the focuswing doesnt move?</p>

 

[sarah_fox]

<p>Good questions here, but the bottom line is that a lens' sharpness has absolutely nothing to do with the length of exposure, whether 1/8000 sec or 8000 days. If you have the 18-55 IS lens (rather than the non-IS), be certain to shut off the IS, or else it will drift, and your image will blur. Put the camera on a good tripod, focus correctly, and you should have no problems.</p>

<p>Incidentally, the IS version of the 18-55 is a very sharp lens. The non-IS is not particularly sharp. </p>

[whiteyphoto]

<p>If you consider how far the moon appears to move between dusk and dawn....several hours....might not it move enough to make it look unsharp in a 5 minute exposure?</p>

[sarah_fox]

<p>"... might not it move enough to make it look unsharp in a 5 minute exposure?"</p>

<p>Of course. I guess I should have specified "... excepting motion blur" ;-)</p>