Focus Issues or ISO - Images Not Sharp

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jamesv

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James
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Okay, so I just got myself a second hand Canon EOS 350D (after Fuji quoted me £150 for a screen repair), with the standard 18-55mm kit lens (the non-IS one). I took myself into London a few weeks ago, to give the camera a try out, especially to see how it performs in low light. Overall, I am quite impressed, but I have a question about the focus on the camera, or what I suspect might be the focus. The images I took just weren't sharp, despite the autofocus system registering that it had a focus, and the focus indicators on the focussing screen lighting up.

An example of what I mean can be seen in this shot:

4426949351_1f6a9c9be1.jpg


It looks good from a distance, but when you zoom in to the picture, the detail just goes. See the crop below.

4427728454_8e537e8752.jpg


The original picture was taken at 18mm (on the 18-55 kit lens), at ISO 200, 30 second exposure at f/10. Post processing was done using Raw Therapee.

I suspect that the ISO may be set too high, but I don't understand how this causes the image to become pasty. I have also done no noise reduction on the image (I know that luminance noise reduction can give a pasty effect like the one above). Camera shake was not an issue as far as I know. There was pretty much no wind, and I used the mirror lock up and the self timer function on the camera, and of course, it was mounted to a tripod.

I have had reasonable results with this camera and lens. This is a shot of Coventry Cathedral, taken at ISO 100, 30 second exposure at f/8. Post processed also in Raw Therapee. The whole of the image is sharp and in focus.

4427762672_3de991032b.jpg


So where am I going wrong?

Thanks for any advice given.
 
To be fair, there doesn't really look to be too much wrong with them, sure there is noise but that's to be expected. I suspect the issue is with the lens, the non-IS kit lens isn't really very good...
 
18mm on a kit lens is always going to be soft ( sorry) but on the bright side thats a very nice shot :thumbs:
 
18mm on a kit lens is always going to be soft ( sorry) but on the bright side thats a very nice shot
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Thanks :) :) :).

I suspect the issue is with the lens, the non-IS kit lens isn't really very good
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So if I was going to upgrade the lens, would something like Tamron 18-200 - http://www.dpreview.com/news/0502/05022105tamron_18-200mm.asp be a good choice. Or should I stick with Canon lenses and get the 18-55mm IS. These both seem to be reasonably priced, and I guess I could stretch my budget to them.

I really wanted to spend my money on something wider, like the Sigma 10-20mm or a Tamron 10-24mm (when uni ends and if am able I get a job over the summer), because I like taking shots of buildings and I like the drama of the wide angle. I was looking at the Canon 10-22mm, but this is waaay out of my budget, and is an EF-S fit.
 
I had (have) these same issues with my 450D and I have found it was NOT the lens. Its the autofocus system - it's completely botched. Me and two other mates have also noticed the quick AF system is softer than a good manual focus, or the contrast detect live view focus, which achieves pin sharp results providing the light is correct.

In light of this I now always use manual focus or contrast detect on live view. Would you like me to post comparison shots?
 
I really wanted to spend my money on something wider, like the Sigma 10-20mm or a Tamron 10-24mm (when uni ends and if am able I get a job over the summer), because I like taking shots of buildings and I like the drama of the wide angle. I was looking at the Canon 10-22mm, but this is waaay out of my budget, and is an EF-S fit.
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Go with Sigma 10-20mm you wont regret it ;)
 
Go with Sigma 10-20mm you wont regret it
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Now I am tempted, perhaps I can live with the 18-55 kit, and pool my resources :naughty:.

However, the Sigma 10-20mm is quite expensive... £479.99 from warehouseexpress.com, plus I will need a UV filter for it, which will mean it'll cost me over £500. On the other hand, the Tamron 10-24mm is £384.99, so over £400 with a filter which is much more affordable. I mean the £100 difference will get me a new tripod :eek:.

Plus I get an extra 4mm on the end. Is the Sigma lens really worth the extra £95?
 
Ditch the kit lens (flog it on here-£25/30) Get the 18-55 IS (around £65 SH) and the 55-250 IS (around £140 SH). I did exactly this and my images improved dramaticaly. Then get the nifty fifty and your images will be pin sharp.
 
jamesv said:
Now I am tempted, perhaps I can live with the 18-55 kit, and pool my resources :naughty:.

However, the Sigma 10-20mm is quite expensive... £479.99 from warehouseexpress.com, plus I will need a UV filter for it, which will mean it'll cost me over £500. On the other hand, the Tamron 10-24mm is £384.99, so over £400 with a filter which is much more affordable. I mean the £100 difference will get me a new tripod :eek:.

Plus I get an extra 4mm on the end. Is the Sigma lens really worth the extra £95?
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I bought the 10-20 for just under 350 on Amazon.
 
So if I was going to upgrade the lens, would something like Tamron 18-200 - http://www.dpreview.com/news/0502/05...n_18-200mm.asp be a good choice. Or should I stick with Canon lenses and get the 18-55mm IS. These both seem to be reasonably priced, and I guess I could stretch my budget to them.
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If you want more quality, dont go for a bigger zoom

Plus have you got the original of that shot, (without processing)
 
andrewc said:
You won't need a UV filter. You might want one, but you don't need one. Lens hood will protect front element.
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Not for night-shots, maybe, as the internal reflections will spoil the shot, but for general outdoor use there's no harm in using a filter for a bit of extra protection.
Image quality will not suffer by any noticable amount in 99% of shooting situations.
 
You didn't say whether you used a tripod or not ;). Assuming that you did, a 30 second exposure may be susceptible to wind and traffic vibration. To counter this and produce tack sharp images would require a tripod probably costing more than your 350D.
If you're getting pasty looking images then that sounds like over-aggressive jpeg noise reduction. Turn NR down, or off, or better still, learn to shoot and process raw and use a separate NR program.

As it stands your test shot looks ok to me.
 
jamesv said:
Thanks :) :) :).



So if I was going to upgrade the lens, would something like Tamron 18-200 - http://www.dpreview.com/news/0502/05022105tamron_18-200mm.asp be a good choice. Or should I stick with Canon lenses and get the 18-55mm IS. These both seem to be reasonably priced, and I guess I could stretch my budget to them.

I really wanted to spend my money on something wider, like the Sigma 10-20mm or a Tamron 10-24mm (when uni ends and if am able I get a job over the summer), because I like taking shots of buildings and I like the drama of the wide angle. I was looking at the Canon 10-22mm, but this is waaay out of my budget, and is an EF-S fit.
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Why are you worried about the fact its an EFS fit? You do know the Sigma 10-20 is 'EFS fit' (Sigma equivalent) as well.

Dont let EFS fit put you off, really, are you going to bother with full frame any time soon? Why miss out on such good lenses?
 
I don't think there is anything 'wrong' there. Just a combination of noise and maybe a bit of diffraction at f/10. Diffraction is an optical aberration that applies to all lenses, not a fault as such - on your crop format camera it will start eating away at fine detail at f/numbers higher than about f/8 (in theory, as low as f/5.6) but is not usually a major problem until f/16.

350D is an older camera, not state of the art sensor wise. Still pretty good, but you're really pushing it there. The older kit lens is also unlikely to be a contributor. The newer version is better though, plus it's got IS of course.

Could also be some vibration going on, even with a tripod. You can't feel it, but it's often there, just blurring things very slightly. Maybe.

If you upgrade, if that is the kind of thing you like to shoot with bright lights at night, do not use a filter of any kind. You are guaranteed to get reflections from the sensor bouncing back off the rear of the filter. Here's a few comparison pictures to put you off ;) http://www.talkphotography.co.uk/forums/showthread.php?t=212297
 
Hi James,

I don't know the camera or lens so cannot comment on them. However, I believe that for what you have got the image is very good.

How could you improve it without spending much money?

Most certainly go to lowest iso.

You obviously had a tripod. Is it a good sturdy one? If not try and change it.

Did you use a remote control? If not get one, they can be very low cost.

Did you use mirror up assuming your camera can do it? You will be surprised at how much shake the mirror moving can make in a photo.

Did you cover the viewfinder to stop any background light getting in?

After all that I would then start looking at different lenses. But don't forget it is a very good image, well done you!

Regards

Chris
 
kit lens is not very sharp
F10 is not sharp due to diffraction
long shutter speeds are not good for sharpness either



the first two pictures are in the distance which makes it mroe difficult to resove the detail the third one is closer and has more light to reveal detail.
 
The AF could be out, or it could just be down to the long exposure. What tripod were you using? Depending on how sturdy the support was, even a bit of wind or people walking past can be enough to move the camera a tiny amount during the shot.
 
alastairb said:
on a 350D diffraction won't kick in until well beyond F10!
hoppy the theory of it starting at f/5.6 and being noticible in fine detail at f/8 are for the 7D due to the very high resolution of the sensor
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I don't think it's relevant to the OP's post here, but since you raise the point ;)

Diffraction is an optical lens aberration and is related to the f/number and the size of the sensor and magnification of the image. As such, it is independent of pixel density. I am aware of the theory re pixel density and airy disc size etc, but have yet to see any evidence of it. The reverse in fact.

Here's a good review of the humble 18-55 IS kit lens on a 40D (10mp). It peaks around f/5.6, with diffraction taking an ever increasing toll thereafter
http://www.dpreview.com/lensreviews/canon_18-55_3p5-5p6_is_c16/page3.asp
 
Just a quick thought, it seems to me you're not comparing like with like. You're cropping and zooming the first image of london, and the cathedral you have the full image. Any cropping will reduce image quality(not sure of your camera but the cathedral will have full pixel density whilst cropped zoom looks like only a 10th or less, so if you have a 10mp camera cropped pic will only be 1mp at best) . Did you take an image in london at 55mm? If you did how does that compare, or try cropping and zooming a portion of the cathedral shot.
 
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