I have a Canon 400D DSLR camera and I am having a lot of trouble with
underexposure. From reading lots of forums I believe that Canon may have
set the defaults in such a way as it brought about the underexposure in
order to stop the highlights being burnt out. I also understand that the
camera's settings can be adjusted to yield a much improved image.
If anyone knows what these settings are I would appreciate knowing what
they are.
Regards
Alan
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"Alan McGrath" <alanm@ihug.co.nz> wrote in message
news:fdstjt$ne9$1@lust.ihug.co.nz...
I also understand that the
> camera's settings can be adjusted to yield a much improved image.
>
> If anyone knows what these settings are I would appreciate knowing what
> they are.
On Oct 2, 3:56 am, "Alan McGrath" <al...@ihug.co.nz> wrote:
> Hi all,
>
> I have a Canon 400D DSLR camera and I am having a lot of trouble with
> underexposure. From reading lots of forums I believe that Canon may have
> set the defaults in such a way as it brought about the underexposure in
> order to stop the highlights being burnt out. I also understand that the
> camera's settings can be adjusted to yield a much improved image.
>
> If anyone knows what these settings are I would appreciate knowing what
> they are.
>
> Regards
>
> Alan
>
> --
> This email along with any attachments is confidential and may be subject
> to legal privilege. If it is not intended for you please reply immediately,
> delete/destroy this email and do not store, forward, print, copy, disclose
> or use it in any way.
Hi Alan,
Yes, the 400D (XTi) does seem to underexpose slightly. And yes, I
think you are right that this is to prevent blown highlights (there is
actually still a lot of detail in the dark sections that can be
brought out with a bit of brightness adjustment especially from a RAW
image). Anyhow, I find that setting the Exposure Compensation to
about +2/3 works quite well. Interestingly though for images in
twilight I've found +1/3 or even no compensation can be better.
If you want to test the best setting, you can start shooting in RAW.
Canon's RAW software allows you to "adjust" the exposure after the
fact by the same 1/3 increments which will give you an idea of the
type of compensation you will generally need. Like I said in my case
it is usually around +2/3 but I do use the histogram display to look
for blown highlights which do on occassion occur forcing me to back
off a bit.
Also, you can use auto exposure bracketing for a while to see what
generally works best for you.
"Alan McGrath" <alanm@ihug.co.nz> wrote in message
news:fdstjt$ne9$1@lust.ihug.co.nz...
> Hi all,
>
> I have a Canon 400D DSLR camera and I am having a lot of trouble with
> underexposure. From reading lots of forums I believe that Canon may have
> set the defaults in such a way as it brought about the underexposure in
> order to stop the highlights being burnt out. I also understand that the
> camera's settings can be adjusted to yield a much improved image.
>
> If anyone knows what these settings are I would appreciate knowing what
> they are.
>
> Regards
>
> Alan
>
>
> --
> This email along with any attachments is confidential and may be subject
> to legal privilege. If it is not intended for you please reply
> immediately, delete/destroy this email and do not store, forward, print,
> copy, disclose or use it in any way.
>
I agree that it underexposes a bit. For jpegs, add about 1/2 stop of
exposure compensation. For RAW, I leave it alone as I can tweak the curves,
but can pull back any blown areas. You may want to bracket important shots.
John
Alan McGrath wrote:
> Hi all,
>
> I have a Canon 400D DSLR camera and I am having a lot of trouble with
> underexposure. From reading lots of forums I believe that Canon may have
> set the defaults in such a way as it brought about the underexposure in
> order to stop the highlights being burnt out. I also understand that the
> camera's settings can be adjusted to yield a much improved image.
>
> If anyone knows what these settings are I would appreciate knowing what
> they are.
>
> Regards
>
> Alan
>
Try posing your question here..... This is the world wide Canon EOS
list.......
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> I have a Canon 400D DSLR camera and I am having a lot of trouble with
>underexposure. From reading lots of forums I believe that Canon may have
>set the defaults in such a way as it brought about the underexposure in
>order to stop the highlights being burnt out. I also understand that the
>camera's settings can be adjusted to yield a much improved image.
> If anyone knows what these settings are I would appreciate knowing what
>they are.
From my reading, there are several different things that may be involved
in what you observe:
1. Traditionally, Canon has built cameras whose actual sensor
sensitivity was slightly higher than rated. For example, when you
select ISO 100, the meter gives you the correct exposure for an ISO 100
sensor (as checked against an external light meter) but the sensor is
really about ISO 120 and the mid-grey in the JPEG image ends up slightly
above what you'd expect for a mid-grey. This often looks better than a
"correct" exposure, but risks clipping highlights.
The 400D/XTi's sensor is not overrated. It's really ISO 100 or less,
probably due to the smaller pixel pitch in its 10 MP sensor. So you get
darker images than most previous Canon DSLRs under the same conditions.
You can compensate for this with Exposure Compensation, though you risk
running out of EC range if you always need +2/3 stop just for normal
low-contrast shots.
2. Apparently, evaluative metering heavily weights the exposure
according to the brightness of the selected autofocus spots, which are
the closest objects if you let the camera automatically set the
autofocus points. This may not be what you want. Several strategies
have been suggested to deal with this:
- Use center-weighted metering most of the time instead of evaluative.
- Only use the center autofocus spot, and aim it where you want before
half-pressing the shutter.
- Use the "*" button to set exposure and focus independently.
3. The camera seems to badly mis-meter light through lenses with a small
wide-open aperture. On my own camera with a 50 mm f/1.8 mounted,
metering a white card, the camera agrees with an external spotmeter to
within a small fraction of a stop. When I switch to the kit zoom lens,
the meter thinks there is about 1/2 to 2/3 stop *more* light, and
underexposes these zoom shots by that much *compared to the 50 mm lens
on the same camera*.
This seems to be a simple flaw in either the metering system or lens or
both. Some people have reported sending their camera to Canon service
and getting this fixed, apparently by a focusing screen swap and meter
recalibration. I ought to do this to mine, but haven't found time yet.
> agree that it underexposes a bit. For jpegs, add about 1/2 stop of
> exposure compensation. For RAW, I leave it alone as I can tweak the
> curves, but can pull back any blown areas. You may want to bracket
> important shots. John
I shoot in RAW all the time. Depending on how "blown" is defined, it's
still not possible to "pull back" a highlight that is actually "blown".
I think it's the definition of "blown" that's the issue. I consider a
highlight to be "blown" when the luminance value equals 255. Some cameras
are less strict. For example, the Canon 5D apparently flashes the blown
highlights indicator for luminance values over 249 (see http://www.brisk.org.uk/photog/hiblow1.html). If the luminance of an area
in an image is 255, then you can not get any detail out of it by post-
processing the RAW file. If the luminance is anything below that, then you
can "pull back" some detail.
On Oct 2, 5:52 pm, Mardon <mgb72...@hotmail.com> wrote:
> "JohnR66" <nos...@att.net> wrote:
> > agree that it underexposes a bit. For jpegs, add about 1/2 stop of
> > exposure compensation. For RAW, I leave it alone as I can tweak the
> > curves, but can pull back any blown areas. You may want to bracket
> > important shots. John
>
> I shoot in RAW all the time. Depending on how "blown" is defined, it's
> still not possible to "pull back" a highlight that is actually "blown".
>
> I think it's the definition of "blown" that's the issue. I consider a
> highlight to be "blown" when the luminance value equals 255. Some cameras
> are less strict. For example, the Canon 5D apparently flashes the blown
> highlights indicator for luminance values over 249 (seehttp://www.brisk.org.uk/photog/hiblow1.html). If the luminance of an area
> in an image is 255, then you can not get any detail out of it by post-
> processing the RAW file. If the luminance is anything below that, then you
> can "pull back" some detail.
Agreed. Again this is one of the speculated reasons that Canon opted
to underexpose on the XTi/400D. You can brighten the dark areas much
better than you can recover a maxed out or "blown" area.
"Bates" <nw1008@gmail.com> wrote in message
news:1191371181.381313.320380@w3g2000hsg.googlegro ups.com...
> On Oct 2, 5:52 pm, Mardon <mgb72...@hotmail.com> wrote:
>> "JohnR66" <nos...@att.net> wrote:
>> > agree that it underexposes a bit. For jpegs, add about 1/2 stop of
>> > exposure compensation. For RAW, I leave it alone as I can tweak the
>> > curves, but can pull back any blown areas. You may want to bracket
>> > important shots. John
>>
>> I shoot in RAW all the time. Depending on how "blown" is defined, it's
>> still not possible to "pull back" a highlight that is actually "blown".
>>
>> I think it's the definition of "blown" that's the issue. I consider a
>> highlight to be "blown" when the luminance value equals 255. Some
>> cameras
>> are less strict. For example, the Canon 5D apparently flashes the blown
>> highlights indicator for luminance values over 249
>> (seehttp://www.brisk.org.uk/photog/hiblow1.html). If the luminance of an
>> area
>> in an image is 255, then you can not get any detail out of it by post-
>> processing the RAW file. If the luminance is anything below that, then
>> you
>> can "pull back" some detail.
>
> Agreed. Again this is one of the speculated reasons that Canon opted
> to underexpose on the XTi/400D. You can brighten the dark areas much
> better than you can recover a maxed out or "blown" area.
>
Yikes! I made a typo. That should have read "can't pull back any blown
areas". If it's blow it blown...The reason to underexpose.
John
Alan McGrath wrote:
> Hi all,
>
> I have a Canon 400D DSLR camera and I am having a lot of trouble with
> underexposure. From reading lots of forums I believe that Canon may have
> set the defaults in such a way as it brought about the underexposure in
> order to stop the highlights being burnt out. I also understand that the
> camera's settings can be adjusted to yield a much improved image.
>
> If anyone knows what these settings are I would appreciate knowing what
> they are.
Take a look at the 3-color histogram before you decide it's
underexposed, sometimes one color will blow out & it's not obvious but
causes color shifts or lack of detail in brightly colored areas.
EOS 400D Underexposure 
Linear Mode
