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tigerminx
tigerminx  9237 forum posts South Africa
8 Dec 2006 - 4:40 PM

Hi guys, I would really appreciate your advice on the following?

Some of you may know I that I recently sent my Canon 30D back to Canon (still under guarantee) to get the focusing screen replaced (smudges) and to have the sensor looked at for quite a serious problem when shooting long exposures.

This is not the first time it has been sent back to Canon. I sent it back two weeks after purchasing it because of the serious amount of dust on the sensor, as well as the focusing screen for the same reason mentioned above. They cleaned the sensor, but claimed to have no stock of the focusing screen.

So the dealer where I purchased the 30D from, explained that Canon had calibrated the sensor (Originally said they would replace it), and when I asked if the focusing screen had been replaced, he felt quite embarrased, because he realised they had not done so. 17 days with the camera?

So I can live with a dirty focusing screen, but what annoys me now, is the ISO expansion (H/3200), when set, shoots a plain black image. So this is now a new problem with the camera. Secondly I tried several long exposures, with IS0 100, and feel that there is still a problem? I have posted a link to the full size image below of a 1015 second exposure (17 minutes) at F8, with the lens cap on. Please help confirm my suspicion.

P.S notice how the noise levels are very low at the top and the bottom of the frame? Is this normal?

So I need to know, do I demand a new camera, or let them have it for another 3 weeks (during Christmas might I add), to hopefully resolve the problems for the last time? Any advice would be greatly appreciated.

17 Minutes @ F8 ISO 100

Thanks in advance.
Bruce.

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8 Dec 2006 - 4:40 PM

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ksh
ksh  9467 forum posts
8 Dec 2006 - 4:45 PM

Time to clean your lens cap its dusty Smile
Tell me what settings you used and I will try it with mine later

kinfatric
kinfatric  9550 forum posts Scotland9 Constructive Critique Points
8 Dec 2006 - 4:46 PM

That noise is appalling there is obviously something far wrong here I'd return it

Helpful Post! This post was flagged as helpful
tigerminx
tigerminx  9237 forum posts South Africa
8 Dec 2006 - 4:51 PM

Don't really have anything to compare it to, so thought it could be normal, but from experience I would have to say it looks shocking as well.

Ken, I used Bulb mode, an aperture of F8, and an exposure of 1015 seconds @ ISO 100. Would love to see your results.

Bruce.

strawman
strawman  1021991 forum posts United Kingdom16 Constructive Critique Points
8 Dec 2006 - 4:51 PM

Given the problems ask for a replacement camera while yours is away.

But are you asking too much. Is a 17 minutes exposure fair for digital technology. It strikes me as a region where film has technical advantages. But expanded ISO should work. Any more experienced able to comment? I will try a 17 min exposure. I normaly give up at @1 min.

dust can get in anywhere any time, so I would have just cleaned it and been done with it myself.

tigerminx
tigerminx  9237 forum posts South Africa
8 Dec 2006 - 4:56 PM

Thanks John, fair comments. But what strikes me is the noise is not uniform, seems to be concentrated in the center but fairly clean at the top and bottom? The noise levels at the top and bottom seem to be more reasonable at that expousre. My 300D never gave these kind of problems.

Results are certainly better than this

Bruce.

User_Removed
8 Dec 2006 - 5:01 PM

Not too sure, it's noise. Thought noise would look evenly distributed, and with coloured smears.
Looks more like dust to me. but I've been wrong before Smile

Henchard
Henchard  92744 forum posts United Kingdom1 Constructive Critique Points
8 Dec 2006 - 5:02 PM

I don't have a 30D but wonder if you have tried using custom function 2 'Long exposure Noise reduction'. Presumeably its there because of a problem with long exposures.

Edit: Although reading other forums I'm not sure if this custom function just turns it off. May be worth a try to see if it does make any difference.

strawman
strawman  1021991 forum posts United Kingdom16 Constructive Critique Points
8 Dec 2006 - 5:05 PM

I would expect the edges of the silicon to be better cooled than the center so any thermal based noise would be worse in the middle. That could be a red herring though.

The thing is you would expect a 30D to be better than the 300D and if they said they would replace the sensor they should have. Can you camera dealer not let you try the long exposure on another 30D in the shop? If you take your memory card with you it would cost them nothing and let you know if it is your camera or they all do it.

Also the missing high sensitivity. Is it that it is only enabled in certain modes? Or id it a weird defect. It might be worth checking the custom functions.

Helpful Post! This post was flagged as helpful
tigerminx
tigerminx  9237 forum posts South Africa
8 Dec 2006 - 5:06 PM

Surely dust isn't blue red and white? Smile

To be honest I have used Custom Function 2 on exposures around 2 minutes, and have not seen any improvement whatsoever? Whether it only works after 10 minutes who knows, but I seriosuly feel it's a waste of time.

Bruce.

strawman
strawman  1021991 forum posts United Kingdom16 Constructive Critique Points
8 Dec 2006 - 5:08 PM

It should not be, you see it maps out thermal noise.

For a 17 min exposure I would have said the noise reduction feature was essential. The 300D automaticaly applies it.

PatrickSmith
8 Dec 2006 - 5:09 PM

Hi Bruce. This should not be happening. With my 350D, I've taken exposures lasting over an hour, many at F8 focused to infinity, and never seen anything like this. No problems with the 5D either. Time to demand a replacement if you can get it. I don't know about why it seems cleaner at the top and bottom. Are you positive that NO light was getting in around the edge of the lens cap? (though that would not explain the noise) Try it again with the camera lens cap on and buried in a dark blanket or something, just to be sure. Do a few more tests, then get a new one if you can. I wish I could offer better advice. Sorry to hear about this.
Patrick

tigerminx
tigerminx  9237 forum posts South Africa
8 Dec 2006 - 5:09 PM

Thanks John, maybe that's a good idea.

Custom Function 8 enables ISO Expansion. If it's turned off you can only use ISO up to 1600. If you enable Custom Function 8 you can select H or 3200. Not sure where else to check really. Defintely worked before Smile

Bruce.

tigerminx
tigerminx  9237 forum posts South Africa
8 Dec 2006 - 5:11 PM

Thanks Patrick, pretty much confused at this point. Definitely no light entering the viewfinder or lens cap, I did exactly what you mentioned above Smile

Bruce.

strawman
strawman  1021991 forum posts United Kingdom16 Constructive Critique Points
8 Dec 2006 - 5:15 PM

Think of the pixels, like buckets set to collect water, and light as a series of taps positioned above the buckets. And the amount of light as setting how much the tap positioned above the bucket is turned on. Now these taps are not perfect and drip water, plus each tap drips a variable amount of water.

To take a picture you empty all the buckets, let the exposure occur and them measure how much water is in each bucket. For a sort duration exposure, the drips are tiny compared to the amount of water caused by the light so low noise.

In a long exposure the drips can get to be a measurable amount of water, and they all do differently. So to reduce noise you do the exposure twice. Once with the light and once without the light. The amount of light is now the difference between the two bucket measurements.

Does that help or do you suddenly, like me, need the toilet?

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