My wife and I have the same setup you do canon 850is and we did a 3 week trip in
Indonesia in Sept/Oct 2008.
(I'm actually a CHDK developer and have my own version of CHDK
that I modified with certain menu preferences)
I Played quite a bit with raw on the trip and took most of the pictures in raw.
So after a few thousand photos I can give some feedback on using the camera
and its use with CHDK vs normal mode.
I'll start of by saying that I think that the normal underwater mode is no good.
You don't want to use that. It will leave your photos way too blue.
Use manual mode with custom white balance. I've done a few posts on this
with sample pictures.
Here are some tips/cautions.
- Canon underwater mode is not very good, don't use it.
+ Manual mode with custom white balance when set correctly usually
generates as good a photo as a CHDK RAW mode.
- If custom white balance is done without the flash and the flash fires
for the real photo, the jpeg photo will be VERY red.
+ If you are shooting with CHDK, you can still recover the image.
- CHDK eats up the battery faster. This is because instead of saving
a single 1-2M file you are now saving a 1-2M file *and* a 10M file for the
raw image.
- when taking lots of raw photos, the battery can heat up and cause
fogging. I never had fogging when not using CHDK but I did
with CHDK. I think it is because
of the extra data saves that eats up the power and causes the heat.
- On my dives we took quite a few photos and I'd get about
1-2 dives with chdk and 3-4 dives without per battery charge.
It depended on how many photos and how much flash was used.
- Don't go over a 4gb card with CHDK. Yes you can do it but then there
are complex booting issues and getting your photos to a PC
is very difficult because the card has to be partitioned and windows
doesn't support multiple partitions on removable media like a SD card.
If you do have a big card you have to swap partitions between boot and data
each time you go back and forth between using it on your camera and
on getting the photos to the PC. It is a real pain, and quite complicated.
- When opening the case small amounts of water drops tend to get into
the camera.
This is the one area that I would have to ding canon on. Look closely
the next time you open your camera after it has been wet. If you look
closely you will see that the way the o-ring works can allow a tiny
bit of water to seep around to the inside of the oring once you open
the case. Also the way the case opens
it very often drops water droplets into the case or on to the camera.
This adds unwanted moisture to the inside of the case on the next use.
- The preview you get on the screen after taking a picture or when reviwing
the photo is the jpeg not the RAW image. You cannot view the RAW images
until you process them. It can be done in CHDK by generatng a jpeg but
its real pain and it won't be as good as what you do on host s/w.
- macro mode goes out much further than you think.
Many times you need macro mode rather than normal mode.
I think macro mode goes to like 20 inches. Which means that at
12-16 inches you need to be in macro mode.
Overall I was happy with CHDK but I don't think it is needed all the time.
Sometimes I would turn it off and just shoot in manual mode.
If you can easily do white balancing then you may want to shoot plain manual instead
of chdk raw.
I used a slate for the white balance card and it works great.
I did have major issues trying to white balance when a flash was needed.
For some reason the white balance screwed quite often. I think it was because
the distance from the slate to the camera was different than the final image
and so the color correction is way off.
For the Caribbean I wouldn't mess with CHDK. There you simply point the
camera at the white sand and do the white balance. It is simple and works
great.
The reason I went with CHDK in Indonesia was that that there is no
white sand there and I wasn't sure that I'd want to constantly do white balance
with the slate. It really wasn't that bad.
There were a few times that the RAW images really saved the day.
I was able to recover some flash photos of a beautiful cuttle fish.
The jpegs were no good. So it definitely is useful.
Below is a link to my wife's web page about our recent
trip to Indonesia and all the photos were taken with canon 850is with
no external flash. Just canon housing.
Bill and Terrie in Sulawesi/
Direct links to some of the photo albums:
(there are many more on the main trip report page)
Bunaken_Underwater_Favorites/
Sulawesi Diving/
Lembeh_Underwater_Favorites/
--- bill