AF on the DRebel: @#%&#

cmr164

JimF was kind enough to lend me his DRebel for a day and I used it to take some shots at a wedding Saturday afternoon/night. I must admit that I like the imager but I do not like the camera. I have a 6 year old 2mp DCS-520 (based on the EOS-1n) and I would not switch to the drebel despite the 6.3mp and better noise reduction at high ISOs. There are several areas where the DRebel falls short, with the 2 worst being AF and WB. I will only address AF here.

The Drebel takes so much time to find focus and has such a high percentage of locking onto weird off-axis objects that I found I had 40 shots out of 186 that were unusable even as snapshots and the bulk of that was due to AF issues. As a contrast, the following day at the post wedding BBQ and with the DCS-520 only 2 shots were tossed out of 113.

Here are 3 examples of focus issues. Click on the images to get the full size camera generated jpegs. (RAW+JPG in camera)

The bench in the lower left is in focus.


Here the wallpaper got the focus.


The girl's hair off to the right got the focus.



These are issues with both low and bright light locking, with locking on moving subjects and with some funky algorithms for guessing which AF point to use.

jimf

cmr164 wrote:

The Drebel takes so much time to find focus and has such a high percentage of locking onto weird off-axis objects[...]
These are issues with both low and bright light locking, with locking on moving subjects and with some funky algorithms for guessing which AF point to use.

I think the bulk of the problem was that you appear to have been using the "full automatic" mode (green square on the selector). In that mode the camera appears to attempt to guess what kind of focusing mode to use, and not do such a good job of it.

I admit to almost never using that mode. When I want a fairly high degree of automation I use "P" mode, but normally I only use that for flash photography (excepting studio photography where I use full manual). In the "creative" modes you set the focus point and it obeys it; normally I leave it on the center point and focus/reframe. Used in that way focusing is highly accurate and typically accomplished in 1/4 second or less using the 28-70 f/2.8 lens you were using. Using the inexpensive 75-300 f/4.0-5.6 lens can be quite slow, however, depending on subject.

Moral of the story: Don't use the highly automated modes on the Rebel. You probably don't want to anyway as they don't support RAW.

I note that the firmware on the 10D is very similar to that of the Rebel, so any problem you see with the Rebel is likely to be seen in the 10D as well. In any case after the first experiments with the camera I had no trouble working with its focussing system, although it is clearly inferior in automatic modes versus my old Olympus C2500L. So don't use it that way....

HarveyMushman

jimf wrote:

I think the bulk of the problem was that you appear to have been using the "full automatic" mode (green square on the selector). In that mode the camera appears to attempt to guess what kind of focusing mode to use, and not do such a good job of it.

My D70 does something similar when in full auto mode. I very rarely use that mode however, so it's not really a problem for me.

cmr164

jimf wrote:

I think the bulk of the problem was that you appear to have been using the "full automatic" mode (green square on the selector). In that mode the camera appears to attempt to guess what kind of focusing mode to use, and not do such a good job of it.

I admit to almost never using that mode. When I want a fairly high degree of automation I use "P" mode, but normally I only use that for flash photography (excepting studio photography where I use full manual).

Maybe in the dark I ended up there. You are correct in that there was a switchover to JPG mode at some point. I was trying for 'P' with the flash and I can not tell from the jpgs which mode the drebel was in:

[tabibito:~/Desktop] cmr% strings */IMG_3164.JPG | more
Exif
Canon
Canon EOS DIGITAL REBEL
2004:05:29 21:38:23
0221
0100
2004:05:29 21:38:23
2004:05:29 21:38:23
IMG:EOS DIGITAL REBEL JPEG
Firmware Version 1.1.1
0100
$3br
%&'()*456789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz
&'()*56789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz

In the "creative" modes you set the focus point and it obeys it; normally I leave it on the center point and focus/reframe. Used in that way focusing is highly accurate and typically accomplished in 1/4 second or less using the 28-70 f/2.8 lens you were using. Using the inexpensive 75-300 f/4.0-5.6 lens can be quite slow, however, depending on subject.

How does the drebel lock focus. On the EOS-1n derived models the buttons for exposure and focus lock are under the thumb.

Moral of the story: Don't use the highly automated modes on the Rebel. You probably don't want to anyway as they don't support RAW.

I did not realise that I was in that mode. In the church with the 85 1.2 I had it in av mode and the rest of the time I 'thought' I had it in 'P'. Although I admit that I didn't even remember that the green modes existed.

I note that the firmware on the 10D is very similar to that of the Rebel, so any problem you see with the Rebel is likely to be seen in the 10D as well. In any case after the first experiments with the camera I had no trouble working with its focussing system, although it is clearly inferior in automatic modes versus my old Olympus C2500L. So don't use it that way....

Now that last sentence is scary. Canon has done really solid AF in the high end cameras and it really is 99% firmware. So why would the Drebel not have the same solid AF. Neither model or mode should really make a difference.

jimf

cmr164 wrote:

Maybe in the dark I ended up there

It was certainly in that mode when it was returned :-).

You are correct in that there was a switchover to JPG mode at some point.

That would probably be the point at which the switch happened, then, unless you switched to JPG mode from RAW, I leave it in RAW mode all the time -- except in the automatic modes where RAW is not supported.

How does the drebel lock focus. On the EOS-1n derived models the buttons for exposure and focus lock are under the thumb.

You know, that's a good question, I'd have to go look at the manual :-). I "lock" it by depressing halfway to get the focus, and then holding the shutter there until I reframe. Exposure lock is under the thumb, I use that fairly regularly.

Now that last sentence is scary. Canon has done really solid AF in the high end cameras and it really is 99% firmware. So why would the Drebel not have the same solid AF. Neither model or mode should really make a difference.

Green mode tries to figure out the subject and select from multiple focusing modes, that much I know. I don't know how well it works on other EOS models, but it clearly has some trouble picking the right mode on the Rebel and the 10D firmware is obviously closely related to the Rebel. As for why Canon wouldn't use the same firmware I think you might ask their marketing people about that. It's probably the same reason they do irritating things like disable RAW format in those modes, or remove exposure modes: i.e. to extract more money from you.

jimf

I "lock" it by depressing halfway to get the focus, and then holding the shutter there until I reframe

I checked the manual and that's the way it says to do it.

On rereading the manual's ditty about full automatic mode I am pretty sure what's happening is a high contrast line falls right on or near an AF point and that's what it picks.

cmr164

jimf wrote:

...
That would probably be the point at which the switch happened, then, unless you switched to JPG mode from RAW, I leave it in RAW mode all the time -- except in the automatic modes where RAW is not supported.
...

Arrrggg...

BTW: Does the Canon s/w show more exif info than 'strings' does? I was surprised not to see the exposure settings and mode.

(taking off now for an afternoon of boating)

Andy

bad focus on the dr?
so sorry to hear you've had difficulty. i've had my rebel a few months now, zero focus issues, across five different lenses. i love the af. lowlight? not a problem i'm really getting great results with the 50 f/1.4. i use manual mode 80-90% of the time, and then aperture priority the rest i would say. i also have it on center pt.

aw

mercphoto

Focus and WB on dRebel

cmr164 wrote:

There are several areas where the DRebel falls short, with the 2 worst being AF and WB. I will only address AF here.

I don't have AF issues, but I seldom let the camera pick the AF point on its own, I like to tell it which focus point to use. And speed of focus will depend on the lens used (i.e USM?). As far as WB goes, I've noticed issues there too. It makes me prefer to use RAW mode so that I can correct the WB after the fact.

Bill

jimf

cmr164 wrote:

Arrrggg...

BTW: Does the Canon s/w show more exif info than 'strings' does? I was surprised not to see the exposure settings and mode.

(taking off now for an afternoon of boating)

I checked with the Canon File Browser and it has a ton of information. Here's a sample:

File Name
CRW_2407.CRW
Camera Model Name
Canon EOS DIGITAL REBEL
Shooting Date/Time
05/14/04 07:34:25
Shooting Mode
Aperture-Priority AE
Tv(Shutter Speed)
1/80
Av(Aperture Value)
8.0
Metering Mode
Evaluative
Exposure Compensation
0
ISO Speed
200
Lens
75.0 - 300.0mm
Focal Length
300.0mm
Image Size
3072x2048
Image Quality
RAW
Flash
Off
White Balance
Auto
AF Mode
AI Focus AF
Parameters
Contrast Normal
Sharpness Normal
Color saturation Normal
Color tone Normal
Color Space
sRGB
File Size
5535KB
Drive Mode
Single-frame shooting
Owner's Name
Camera Body No.
0960300463

pathfinder

andy wrote:

so sorry to hear you've had difficulty. i've had my rebel a few months now, zero focus issues, across five different lenses. i love the af. lowlight? not a problem i'm really getting great results with the 50 f/1.4. i use manual mode 80-90% of the time, and then aperture priority the rest i would say. i also have it on center pt.

aw

Like jimf suggested - the 10D is very similar to the Rebel in its AF modes - And like Jim and Andy, I learned very quickly to use the center AF point and recompose with the shutter at half cock. You can chose the AF point in the Creative modes and that also seems to work fine, but flying on Autopilot - the Green modes landscape, macro, portrait etc - shifts from RAW to jpgs and does not handle focus issues well at all. I have thought for some time that this is the source of many of the complaints on the web about focus issues with the 10D - that people were shooting in the Green modes.

I find that using the center AF point and recomposing in the Creative zone solves those issues completely. It is not a 1series camera, but is focuses pretty good unless the light is really low ( > 5 sec exposures for instance ) and the target has low contrast.

jimf

pathfinder wrote:

I find that using the center AF point and recomposing in the Creative zone solves those issues completely.

I mucked around for awhile with changing AF point to be appropriate for the image but it's a lot faster and less error prone to just use the center point. Since moving to that style (which is exactly the way I used to do it with my old Olympus) I've not had any AF issues at all. In fact, the thing focuses better than I do virtually all of the time.

I think that's kind of funny since one of the primary requirements I had for the camera was that it have manual focus capability.

pathfinder

jimf wrote:

I mucked around for awhile with changing AF point to be appropriate for the image but it's a lot faster and less error prone to just use the center point. Since moving to that style (which is exactly the way I used to do it with my old Olympus) I've not had any AF issues at all. In fact, the thing focuses better than I do virtually all of the time.

I think that's kind of funny since one of the primary requirements I had for the camera was that it have manual focus capability.

One of the choices Canon made to keep the price down on the 10D and the Rebel is that there is no provision for interchangeable screens in the pentaprism - this means that there is no split image rangefinder or Fresnel screen - thus manual focusing is very difficult especially in dim light like a slot canyon.

I agree that using the center AF spot is much faster and easier if you are shooting handheld and that is what I do - On a tripod, it can be easier to chose the appropriate AF point in real dim light situations due to the difficulty of manual focus. This is one area where the 1 series cameras shine - they can accept different screens for the pentaprism and thus are better equipped for manual focus in those situations.

fish

I haven't noticed any non user error related focus problems on my 10D. Even with 3rd party lenses.

In looking at the sample photos at the beginning of this thread, it looks like the AF locked onto the background wallpaper. Green box is bad. Put it on P for snapshots, then use your registered AF point. Green box bad.

Andy

canon 10d af

fish wrote:

I haven't noticed any non user error related focus problems on my 10D. Even with 3rd party lenses.

i recently upgraded to the 10d. i love this box! focus is great, with all my lenses. i use centerpt, 1shot for most stuff, and also ai servo for moving subjects. i shoot in manual mode mostly, and av sometimes.

love the performance of this camera.

tmlphoto

andy wrote:

i recently upgraded to the 10d. i love this box! focus is great, with all my lenses. i use centerpt, 1shot for most stuff, and also ai servo for moving subjects. i shoot in manual mode mostly, and av sometimes.

love the performance of this camera.

I also use the center point. You can make this a custom function so that the left thumb button defaults to the center AF. It will stay there until you change it.

cmr164

fish wrote:

I haven't noticed any non user error related focus problems on my 10D. Even with 3rd party lenses.

In looking at the sample photos at the beginning of this thread, it looks like the AF locked onto the background wallpaper. Green box is bad. Put it on P for snapshots, then use your registered AF point. Green box bad.

For sure green box is bad. It was a real stumble to end up there and my only excuse is that I hadn't experienced green modes, it was a borrowed camera, and I switched in the dark. That said, there is no real excuse on Canon's part for providing such brain dead programming. AF should work in all the modes that a camera uses.

The uploadable 3d party firmware that 'fixes' many of the dRebel's dumbed down features and makes it more like a 10d is an indictment of Canon to some extent.

fish

cmr164 wrote:

my dog ate my homework.

fixed it for you, charles.

Andy

that was the first custom function i set ;-)

tmlphoto wrote:

I also use the center point. You can make this a custom function so that the left thumb button defaults to the center AF. It will stay there until you change it.

andy

ginger_55

re dRebel and problems.

jimf wrote:

I think the bulk of the problem was that you appear to have been using the "full automatic" mode (green square on the selector). In that mode the camera appears to attempt to guess what kind of focusing mode to use, and not do such a good job of it.

I admit to almost never using that mode. When I want a fairly high degree of automation I use "P" mode, but normally I only use that for flash photography (excepting studio photography where I use full manual). In the "creative" modes you set the focus point and it obeys it; normally I leave it on the center point and focus/reframe. Used in that way focusing is highly accurate and typically accomplished in 1/4 second or less using the 28-70 f/2.8 lens you were using. Using the inexpensive 75-300 f/4.0-5.6 lens can be quite slow, however, depending on subject.

---

OK, I have been wondering why I couldn't half cock the shutter and have the focus stay. I did that for years with film and my Nikon.

I use P a lot, and I also use Sports, which I heard disparaged constanly on dPreview, but I guess I am an impatient shooter, most things that I shoot move, I find that the second shot is usually the best......etc.
I also so use the last automatic setting so the flash won't come on.

I was thinking that if I wanted to do any evening photography that probably the easiest thing to do would be to use the aperture priority.

But I don't know what you all mean when you say you set the center point. Is that something you do to the camera and leave it that way?

Also I am having trouble with the whatever % grey. I know that one of these challenges I am going to end up out at night, and I don't want my camera thinking it is daylight and going "grey" on me.

I tried messing with the minus and plus two thing, did something wrong, can't figure out what. I want that to work so that I can underexpose. I assume that is what it does. Yes, I do have a manual. I was trying to read it in the dark the other night, but that was because I was not properly prepared, but I am a busy person these days, lots of new things, like 4 folders on shots of the quality of light.

Anyone have any spare moments for advice, smile?

Oh, I rarely have problems with focusing, and I don't know why. Over the years I have picked up some tricks I use, don't even know if they are working with the Rebel, but my pictures are usually in focus. I usually focus on something stationary around the area I really want my focus to be on, something large enough. I tried to explain that to someone on dPreview, and he never did pay any attention to me. The darn camera is really kind of dumb about reading people's minds, that is how I see it, if I were a camera, I wouldn't know that someone wanted me to focus on that little bitty bird way over there, not when there is all that nice folliage to focus on somewhere else.

ginger

ginger

mercphoto

AF on D300

ginger_55 wrote:

I use P a lot, and I also use Sports, which I heard disparaged constanly on dPreview, but I guess I am an impatient shooter, most things that I shoot move,

Try using shutter priority. Pick the shutter speed you want, depending on the amount of stop-action or motion-blur you are looking for. I just try to avoid the basic modes at all costs.

ginger_55 wrote:

I was thinking that if I wanted to do any evening photography that probably the easiest thing to do would be to use the aperture priority.

I use Av for nearly all photography except sports, which I switch to Tv for. I use P if I'm using flash, which is rare for me.

ginger_55 wrote:

I usually focus on something stationary around the area I really want my focus to be on, something large enough. The darn camera is really kind of dumb about reading people's minds, that is how I see it, if I were a camera, I wouldn't know that someone wanted me to focus on that little bitty bird way over there, not when there is all that nice folliage to focus on somewhere else.

Yup. By the same line of reasoning, why have the camera guess at the shutter speed you want for your moving objects by using Sports mode versus Shutter Priority?

cmr164

mercphoto wrote:

Try using shutter priority. Pick the shutter speed you want, depending on the amount of stop-action or motion-blur you are looking for. I just try to avoid the basic modes at all costs.

When I was shooting the Motorcyle races at NHIS I quickly learned that I wanted the 1/800th Tv and let the aperture fend for itself. I am looking forward to my next trip as that was my first try at any kind of vehicle racing.

mercphoto wrote:

I use Av for nearly all photography except sports, which I switch to Tv for. I use P if I'm using flash, which is rare for me.

I use P and liberal spinning of the dial unless I know shutter will be my constant worry (sports/action) or aperture/DoF. On rare occasions I will set the camera at f16 Av, set the focus to a fixed point and just shoot while depending on the DoF. By cutting out the focus lag you can speed the response right up.

mercphoto wrote:

Yup. By the same line of reasoning, why have the camera guess at the shutter speed you want for your moving objects by using Sports mode versus Shutter Priority?

Like someone said earlier and I can vouch for, "Green mode bad."

mercphoto

Racing photos

cmr164 wrote:

When I was shooting the Motorcyle races at NHIS I quickly learned that I wanted the 1/800th Tv and let the aperture fend for itself. I am looking forward to my next trip as that was my first try at any kind of vehicle racing.

Racing can be tough. Probably the best way to judge shutter speed is to look for signs of motion in your pics. If the pics cannot be distinguished from a stationary posed picture then the shutter is too fast. A lack of wheel blur is the first sign. But too slow a shutter and you get issues of camera shake, or of the subject itself moving through the image. In that case you need to accurately pan the camera to follow the subject while the shutter is open. Hard to do, but works great when you can do it. See the Formula One pics that were posted here (forget who did it, sorry) and his shots at 1/100th a second. Very skilled. I'm not that good yet. Sigh.

I take kart and motocross pictures at 1/250 to 1/400 a second shutter, but they aren't moving as fast as your sport bikes are.