300D autofocus

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Trevor Page
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Joined: Oct 4 1999

My 300D is 18 months old now, and I suppose I'd class myself as an experienced beginner :confused: . (Being the first time I've actually used creative settings on an SLR in any depth.)

One thing that has come to my attention is the tendency to front focus when using various lenses wide open (Canon 50mm f1.8, Sigma 70-200mm f2.8)

Is anyone else experiencing similar issues?

Trev

rongrover
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Joined: Jun 1 2002

Hi Trevor. Not sure if I have understood your question right as I am sure you know more about this than I do. But. When you say it has a tendency to front focus, do you mean the camera focus is on the item in the front of the shot?
If so, than as I have understood it, it always will focus on the item nearest the camera.

I have only been using the 300D for a couple of weeks, mainly in portrait mode and using the 50mm f1.8 lens as you are. It really is great for portraits. I always want my person as being the nearest object to the camera and am pleased that the camera will focus on the neearest object with the background very nicely out of focus.

If this is not what you meant, I am sorry for seeing it the wrong way.

I have just had delivery of a full studio set-up of Elinchrom Studio Flash, so have a big learning curve on that now.

All the best, Ron.

Philip Woods
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Joined: Feb 7 2002

Trevor,
I too have had similar problems with Focus Hunting(My words)!
On giving the instruction manual a good peruse, Page 64 identified my problem (When Autofocus Fails)
The EOS-300D I am very pleased with, its my best digital camera so far!

Good Success!

Philip

Trevor Page
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Joined: Oct 4 1999

Ron,
What I mean is, that say I manually select a focus point - for arguments sake the centre point. Then I compose a shot with the centre focus point on say my pet dogs eye, and take the shot. 50mm f1.8 @7 ft.

Examining the image reveals the actual DOF extends from just behind the dogs eye to the tip of its nose.

So the focus point is not in the middle of the DOF, rather it is towards the rear of the DOF. This means that when taking portraits with a very narrow DOF I have to focus slightly further back than the subjects eyes in order to get the focus where I want it.

see: http://www.canon-dslr.com/Canon_Jan05/Canon_SLR_Focus_Test.htm

Philip,
The autofocus is not failing as such, it's just not quite where I'd like or expect it to be.

Trev

rongrover
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Joined: Jun 1 2002

Hi Trevor. Like I thought, I got it all wrong.
But I like the link you gave, will see if I can learn from it.

All the best, Ron.

Trevor Page
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Joined: Oct 4 1999

Cheers Ron. Good luck with the flash, if it were me I'd expect many sleepless nights ... ;)

Expecting my new toys this w/e (20D, 17-40L)

Trev

Philip Woods
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Joined: Feb 7 2002

Trevor,
I have just completed a series of tests and my 300D is focusing behind my chosen spot!
With the limited DOF at f1.8 in close-ups this is grim!
Pluging on my old Pentax in-line magnifier and doing a manual focus test, prooved that all was well in the manual setup!
Gave my Fugi S7000 the autofocus test ? " Spot on".
Now the fault is known, I can make adjustments!

There won't be, in My emails to Canon though!

Thanks for this exposing this EOS-300D fault!
Appreciated,

Philip

Trevor Page
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Joined: Oct 4 1999

Philip, I know how you feel ...

The thing is though that with consumer level Canon DSLR's, (anything less than a 1 series) the spec is for the autofocus to be anywhere within the DOF. So in my case, the camera is performing within spec. :(

I'm fairly sure it's been like this from day one. But now the camera is 18 months old and out of warranty I expect any adjustment that Canon could do would cost. Still I suppose it's worth an email .

And guess what the first thing I'll be doing with my 20D is ... :mad: :mad: :mad:

Trev

g3vbl
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Joined: Sep 9 2000

Trev, the url paints a fascinating picture; thank you for drawing it to our attention. Since I mostly use the kit lens, well stopped down, it has not been as evident but it does make me reconsider the purchase of the 50mm for its wide-aperture capabilities.

Chris

Gavin Gration
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Joined: Jul 29 1999

What you are seeing is not a fault and is true for all lenses.

The zone of sharp focus (a.k.a. Depth of Field) is 1/3 behind and 2/3 in front of the subject being focussed on.

If "S" is the subject & "0" is the out of focus area then the zone of sharp focus is as follows.

Camera> 00000000[------S---]000000

The effect is more noticable with wide apertures when the camera is closer to the subject. It is also more evident at longer focal lengths.

Hope this helps.

On a slightly different point there are not many lenses that are sharp wide open. A 50mm f1.8 is an excellent indoor lens but not necessarily because it's "O.K." wide open.

When you look thro the viewfinder you will see the image at the widest aperture of the lens no matter what you have it stopped down to. Only when you release the shutter or press the DOF Preview button does the camera actually stop the aperture down.

The benefit here is that your eye sees a bright image and the autofocus system gets the light it needs to do its job.

Gavin

Alan McKeown
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Joined: May 9 2001

Quote:
“The zone of sharp focus (a.k.a. Depth of Field) is 1/3 behind and 2/3 in front of the subject being focuessed on.”

The depth of field behind the object being focussed on is always greater than the depth of field in front.

Alan

Gavin Gration
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Joined: Jul 29 1999

Alan - you are of course correct.

I got it back to front & hang my head in shame :(

I need more coffee.

rongrover
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Joined: Jun 1 2002

There is a 6 page article on the subject of Depth of Field in the current (March) issue of EOS Magazine. Also highlights what each Canon Camera can do.

All the best, Ron.

Alan McKeown
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Joined: May 9 2001

The “1/3 in front and 2/3 behind” case (ie. where the rear depth of field is twice the front depth of field) occurs when the focussed object distance is one third of the hyperfocal distance.

But in Trevor’s example:
“Then I compose a shot with the centre focus point on say my pet dogs eye, and take the shot. 50mm f1.8 @7 ft.”...

the rear depth of field (DOF) will only be about 10% greater than the front DOF.

And if the lens is focussed on an object at the hyperfocal distance, the rear DOF will be infinitely greater than the front DOF. (Since the front DOF will be half the hyperfocal distance and the rear DOF will be infinite).

Alan

g3vbl
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Joined: Sep 9 2000

... my interest in a 50mm was simply to reduce the DOF for portaiture. Perhaps Photoshop makes this no longer necessary

Chris

Philip Woods
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Joined: Feb 7 2002

Wide area, high speed focusing
7 selectable focusing points give an ultra wide AF area generally only found in advanced SLRs. Focusing modes include One-Shot AF
(for fast, "Accurate" "Single-Shot Focusing"),
and AI AF which can automatically switch to AI servo AF for continuous tracking of subject movement ­ well suited to sports photography. A Manual Focus override is selectable from the lens.

Canons statement on the EOS-300D Camera!
"Accurate" focus means what it states!
If Trevors dogs nose is in focus, (Instead of its eyes) "What you are seeing is not a "fault" and is true for all lenses".
I do have to state "Reality" has now jumped out of the window!
My tests were taken at 31"(78.7cms?)

The focusing was/is inaccurate!

Trevor Page
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Joined: Oct 4 1999

Using Gavin's example:

Camera> 00000000[--------S-]000000

Is what I seem to get with the 300D No matter what the lens. I'd be happier with

Camera> 00000000[----S-----]000000

I'm experimenting with the 20D today, but can already say that the focussing appears to be spot on

Trev

Alan McKeown
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Joined: May 9 2001

Quote 1:
“So the focus point is not in the middle of the DOF, rather it is towards the rear of the DOF”

Quote 2:
                      
“Using Gavin's example:

Camera> 00000000[--------S-]000000

Is what I seem to get with the 300D No matter what the lens. I'd be happier with

Camera> 00000000[----S-----]000000 “

I think we need to make a clear distinction between the actual plane that the lens is focussed on as against the plane that is the set-point for the auto-focus servo system.

The two planes should of course ideally be coincident. Clearly that is far from the case here. As Phillip writes, the auto-focussing was/is inaccurate.

The “S” in Trevor’s “diagram” above represents the auto-focus set-point plane but the "O"s are related to the actual lens focussing plane. In Gavin’s original diagram the “S” represented the plane that the lens was focussed on.

Gavin’s statements that “What you are seeing is not a fault and is true for all lenses.” and “The zone of sharp focus (a.k.a. Depth of Field) is 1/3 behind and 2/3 in front of the subject being focussed on“ are both incorrect, as has already been mentioned.

Alan

Philip Woods
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Joined: Feb 7 2002

Alan,I think you will have gathered, that I am stressing on the #(for fast, "Accurate" "Single-Shot Focusing")# part of their inaccurate statement, in their advert!
Having made photography my hobby as a ten year old, along with my late brother John and now after sixtyseven years, I have a fair knowledge of film/digital cameras and how use them!

The focusing problem is resolvable!
My Fugi S7000 focusing system, lets me focus on my grandchildrens eyes with great ease!
Childrens eyes really do photograph beautifully!

If the EOS-300D Focusing was correct,the DOF would take care of itself (The DOF is spot-on when I manualy focus the f1.8 50mm(= to 80mm) lens on the camera)
My late Dad use say "State what you mean and Mean what you say" He hated deviosity in any form.
Including Canons:
("Accurate" "Single-Shot Focusing)

My Fugi S7000S can and my Canon 300D canny.

Philip
ps I wonder how Trevor is getting on with his EOS-20D.
=================================================

What's so special about the centre focusing point of EOS digital cameras?
The centre focusing point on the EOS 10D (as well as the EOS D30, D60 and 300D) is a cross-type sensor which works with all EF lenses or lens/extender combinations that result in a maximum aperture of f/5.6 or larger.

All focusing points on EOS 300D/10D/D30/D60 are considered 'normal-precision' regardless of the maximum aperture of the lens. 'High-precision' AF sensors are available exclusively with the EOS 1Ds, 1D and 1D Mark II among EOS digital SLRs.

What do we mean by 'normal-precision' and 'high-precision' AF? A normal-precision AF sensor produces focusing accuracy within the depth-of-focus for the lens' maximum aperture. A high-precision AF sensor produces focusing accuracy within 1/3 the depth-of-focus for the lens' maximum aperture. When activated, high-precision AF sensors have up to three times the precision of the normal-precision sensors.

(Depth-of-focus is not the same as depth-of-field. Depth-of-focus refers to the zone of focus within the camera. You can think of it as the distance the sensor could move forward or back while still recording a sharp image.)
===============================================
The above is from Canon!
It most certainly does not apply to my EOS-300D With the f1.8 mk2 in use1
Tests were taken at 31"(78.7cms?)at F1.8, All the points focused on were not in focus!
on moving the camera forward 2" (Two inches)5 cms! and locking the focus before moving the camera! Click! On checking the image all was now well ! With the near and far distances running in and out out of focus they should!
A sideways on "Stereo slide unit" anyone ?

Trevor Page
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Joined: Oct 4 1999
Quote:
Originally posted by Philip Woods:
ps I wonder how Trevor is getting on with his EOS-20D.

Sorry for the delay, have to work sometimes :(
Well after much testing with a half decent lighting setup, I'm pleased to say that the 20D is much better than the 300D. The focus achieved by the autofocus system does coincide with the centre of the depth of field of all my good glass when at or near wide open. Well 99% of the time it does which is good enough for me.

Trev

Philip Woods
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Joined: Feb 7 2002

The 50mm f1.8 is the problem, the autofocus is wrong all of the time + the D.O.Field Preview is not working. (Manual focus @ f1.8 is fine though!? (So,back to Jessops!))
================================================
The other two expensive pieces of glass purchased are ok!
A 42mm to OES adapter, VIA the morning post has made all my Pentax Super-Takumar lenses available for usage!!!!!!!!!!!!
A EOS-20D is in the offing (It does have a great deal of advantages over the 300D!

No need to answer, just rue-minating over the 300D!
-----------------------------------
Philip

Trevor Page
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Joined: Oct 4 1999

20D v 300D quick resume of the features/advantages that I love about the 20D over the 300D.

Faster more accurate focussing
Quick review and quick power on
Continuous shooting
Choice of AF modes AI servo is fun!
Dual dials and joystick control of AF point selection
Usable low light ISO up to 1600
Digital Photo Professional

What I don't like -

The hole in my pocket caused by the 'need' for more glass and more CF cards and a better Tripod... Oh and I bought Noise ninja plugin - very impressive. And tyres and petrol for all those places I'm visiting to play with my new toy ;) The black eye from the missus when she see's the credit card bill at the end of the month.

Trev

Philip Woods
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Joined: Feb 7 2002

My 20D should arrive by Tuesday />, That should absorb more of my time in getting familiar
with the added functions!

Canon EOS-20D EF-S 18-55mm f/4-5.6 LENS + Sandisk Ext 111 X133 C/Flash + BGE2, cost: £1049

Then getting shot of the 300D,As I think my "old beloved" would notice the great similarity
between the two cameras and one eyebrow would be raised!

Hobbies like Amateur radio, Model engineering (Mainly building 5" Guage Steam locomotives)
etc have enured her to most of my ways ?

Continuous shooting.. The 300D has 4 shots in sports mode.
Usable low light ISO up to 1600 ? 3200 (H) Via Wasia Firmware hack with me

If my wife knew the cost of the two lenses?, Although when they are placed among my other
Pentax lenses, Who can tell!!!!

I Downloaded the photoshop 'Noise ninja' plugin,I must say the web photo's - before and
after - Really are very good on showing its capabilities!

Agreed, Running costs can get a little high!
A good tripod will add stability to both you and the camera!
Using the tripod in the defensive mode, is course rather ungentlemanly like!
Rapid avoidance or a well placed ice-cream cone will take care the eye!

Going on hols begining of the week,Up north to Avimore,to see our son Andrew and family so
can only hope the weather is reasonable!

Enjoy the camera,
-----------------

Philip

tim
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Joined: Mar 27 1999

Philip,

I have been very interested to read your postings.

Like you, I have just "upgraded" to a 20D from a 300D and can only say "wow", what a difference in speed between the two.

At present I am very reluctant to say goodbye to the 300D and am considering passing it down the "food chain" to one of my offspring. Have no fear, the 20D looks very little like the 300D and "er indoors" at my address would, I think, (rather, I hope) not be too suspicious, A bit like you I have immersed myself over the years with R/C models of boats, motorbikes, aeroplanes and helicopters. Currently, apart from video and stills I am fairly far down the line of building a quarter size live steam model traction engine.

I am delighted with the 20D after only a week of ownership.

Tim

Philip Woods
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Joined: Feb 7 2002

Hello Tim,
Back again after an overnight at my youngest daughter home!
I know now the 300D was an error on my part and since my family are all "small" camera minded, the 300D size with BG-E1 would be a no-no!
All the 20D info was thoroughly checked and its spec suits my needs, much more so than the 300D!

The camera look-a-like bit was me jesting, after 47 years of marriage, Ann has given up hope!

Modeling started when I was 13, Building and flying gliders, as rubber was very scarce then!
After WW2,The "Hivac" valve and Goverment Surplus, Let my brother and I build our first radio (minimally) controlled plane (By rudder)!
We were both working in the radio industry then!
Then it was into Tuned Reed /Galloping Ghost and so on, into the Digital systems we know today!

Never tried model motorbikres or helicopters, enjoyed Pylon 40's/Aerobatitic(When younger)/ and WWI Scale Biplanes,All now reposing in my attic as they wont fit into my car!
Still flying the small electric parkfly though, keeps my 77 old mind and fingers active!!!!

Been filming my family as grew up using Standard 8/ Super 8 and there are stacks of 200 ft reels in
my radio room!
I amuse the grandchildren by showing a reel now and then letting then watch the antics of their parents (Doesn't amuse the parents at times!)

Yes Digivideo/stills make the hobby a lot simpler, than it used to be!

Fine on the building a quarter size model steam traction engine,That is very large by our clubs measure, 1.1/2" and ,2" to the foot, We do have though!
Yes, its nice getting our "fix" of steam oil via the chimney stack!

I too will get acquainted with the 20D when on holiday this week, Hopefully I'll be Canon praising this Easter!!!
.......................

Philip

tim
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Joined: Mar 27 1999

Hello Philip,

Great to read your posting, a very similar profile to myself, although your 47 years of "wedded bliss" beats mine by a couple of years!

I know you will thoroughly enjoy the 20D as much as I am enjoying mine.

Regards,

Tim