Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Canon EOS dSLR

Reply
 
Thread Tools Search this Thread
Old Jan 23, 2004, 5:18 PM   #1
Junior Member
 
Join Date: Jan 2004
Posts: 5
Default 10D Exposure Question

Hi,

I am a digital point and shoot user who is thinking of moving up to a digital SLR. I recently had a chance to try a Canon 10D and I was wondering if someone could explain what I saw.

I found it consistently underexposed the image by about 0.5 to 1 stop. The only time it did not was on a cloudy day with very uniform lighting. I went to a camera store to ask them about it and I tried out one of their 10D's and found exactly the same thing.

The people in the shop could not explain why the exposure seemed to be dark. Basically, the explanation they gave me was that most SLR users don't use the metering in the camera.

To the photos were all taken out of doors and the conditions had a lot of contrast. Still my G2 handled the contrast fairly well (however, I don't know what the G2 is doing to help me behind my back).

Since two 10D's showed the same behavior I have to conclude that they were working properly.

Does anyone know why the exposures might seem dark?
Caveat is offline   Reply With Quote
Sponsored Links
Old Jan 24, 2004, 2:10 AM   #2
Junior Member
 
Join Date: Jan 2004
Posts: 13
Default

Caveat, there are several things missing here. First, what metering and or creative/basic zone modes were you in when you did these tests? Second, were any parameters set in the camera for shooting? Third, what was the LCD setting for brightness in the Menu catagory? This along with other things will affect your viewing of images on the camera. If you are shooting and viewing the images on a computer there are several other things you would need to look at. But first I would look at the histogram on the camera in the Review/Info and see if it maps out. If you are just looking at the LCD that's not exactly what you're getting. Another way to check would be to go and take a few images and check them out with Photoshop and look at the values for highlights, midtones and shadows. I shoot with the 10D and haven't had any problems with exposure except using the 550EX flash, then there were some underexposure problems. Good Luck! Bob
Fotobob is offline   Reply With Quote
Old Jan 24, 2004, 4:42 AM   #3
Junior Member
 
Join Date: Jan 2004
Posts: 5
Default

Hi Photobob,

Thanks for the reply. When I did the photos I had the following set:

ISO 100
Av Mode
EV 0
Evaluative Metering Mode

I viewed the photos on my computer monitor. When I looked at the histograms the top quarter of the upper range was missing. The images seem a little muddy as well.

If I fiddle with the levels in photoshop the images really improve.

The conditions were not the best. There was a lot of snow on the ground. However, I found I had the same problem occurred if I pointed it at something neutral like a stone wall.
Caveat is offline   Reply With Quote
Old Jan 24, 2004, 5:57 AM   #4
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

Quote:
I found it consistently underexposed the image by about 0.5 to 1 stop. The only time it did not was on a cloudy day with very uniform lighting. I went to a camera store to ask them about it and I tried out one of their 10D's and found exactly the same thing.
The 10D (like the Digital Rebel) metering is evaluative and centered around their seven different AF focus points:

o With a uniform lighting every sensors around each AF point would pick up the same EV value.
o With bright or contrasty subject, the EV is based around which AF point is lit up even though the camera hasn't moved, ie the camera will 'evaluate' the scene and put more biais (weighting) around the AF point it picks! If an AF point picks up a brighter area it will underespose, while it will overexpose if another AF point lands on a darker area...

-> Changing to the center AF point only will make the metering more consistent, or try center and spot metering.


Quote:
I shoot with the 10D and haven't had any problems with exposure except using the 550EX flash, then there were some underexposure problems.
The evaluative metering works the same for flash... and will vary with the background that was picked by any of the AF sensor; This will get you everytime when a subject wear lighter clothes like wedding dress... (or overexpose on the groom with darker suit). It all depends on where the AF point landed on.

If one use the Flash Exposure Lock (FEL) however, only the center area is metered. Try it, it'll lock on the exact area you want to meter! BTW this is an area where the Nikon or Minolta system excel over the Canon because it takes the subject distance (D info from the lens) and modulate the flash output accordingly... 8)
NHL is offline   Reply With Quote
Old Jan 25, 2004, 6:26 AM   #5
Junior Member
 
Join Date: Jan 2004
Posts: 5
Default

Hi All,

When I had the 10D I did a quick comparison with my G2. I took a bunch of shots out with the 10D and then I took a bunch of shots of the same view with my G2. The G2 shots were much brighter and the did not have the underexposed look that the 10D ones had.

Yesterday I spent a while playing on PhotoShop with the images. I had found that setting the levels cleaned up the 10D photos quite a bit. However, what I found yesterday was I could get pretty much the same results just by adjusting the contrast and brightness levels. In fact with a little tweaking on the G2 shots and the 10D shots I got them looking pretty much the same.

The 10D images took quite a bit of contrast adjustment (about +30) to really clean them up. Would anyone know if the G2 default contrast setting is much higher than on the 10D? The G2 is just a consumer camera so I could see Canon fiddling with this.

Also, on a 10D is it normal to expect the images to require such a contrast adjustment right out of the camera?
Caveat is offline   Reply With Quote
Old Jan 25, 2004, 7:54 AM   #6
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

You can go to the user1 and 2 settings and match the results of the 10D to your other camera, but is this what you want?

Underexpose is actually 'good'... one can normally recover from, unlike an overeposed shot which usually clips the highlight... same with contrast. You can increase the contrast, but decreasing will usually leave out the details. May be what I try to say is the default setting on the 10D errs on the safe side giving you more room to 'fiddle' with Photoshop...

There's always RAW! :lol: :lol: :lol:
NHL is offline   Reply With Quote
Old Jan 25, 2004, 8:22 AM   #7
Junior Member
 
Join Date: Jan 2004
Posts: 5
Default

Thanks for the reply NHL. Now I have a new question

You mention RAW format in your last message. Does shooting in RAW affect things like contrast?
Caveat is offline   Reply With Quote
Old Jan 25, 2004, 9:12 AM   #8
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

Quote:
You mention RAW format in your last message. Does shooting in RAW affect things like contrast?
No!

All the camera settings are tagged and include along with the RAW information for later processing in the computer, but the data that was read from the sensor are not affected in any way by any of the camera settings... 8)
NHL is offline   Reply With Quote
Old Jan 26, 2004, 10:39 AM   #9
Junior Member
 
Join Date: Jan 2004
Posts: 5
Default

Interstingly, while researching digital camera exposures on the web I found this web site that states digital camera users should push the histogram as far to the right as possible without clipping the data.

http://www.luminous-landscape.com/tu...se-right.shtml

Which is the exact opposite of what I saw the 10D doing. I am not sure I get the argument though. If the exposure properties of the CMOS are linear as the site states wouldn't you get the exact same number of levels in each range?
Caveat is offline   Reply With Quote
Old Jan 26, 2004, 8:33 PM   #10
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

Quote:
If the exposure properties of the CMOS are linear as the site states wouldn't you get the exact same number of levels in each range?
The number of levels in each range is a function of the scene... linearity is good for any sensor, but not representative of any particular grouping. The image content disctates how the levels are shaped: http://www.luminous-landscape.com/tu...stograms.shtml

The result wouldn't be too good if you push this histogram to the far right for example: http://www.luminous-landscape.com/1p.../pq-moon.shtml

What the camera try to do in Auto is to control the exposure so that both sides of the histogram stay inside the 0-255 range, but then in some scenes the dynamic range is just so large that some clippings (either shadows, highlights, or even both) will occur anyway!

BTW when you increase contrast you're actually spreading the levels apart!
NHL is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 8:56 AM.