Canon EOS 40D autofocus and behaviour...

02/05/2008 11:09:33 PM · #1

Hi guys, long time no see, for several years I've been reading and seeing the pictures on DPChallenge, but no discussion at all.

Last weekend I've been gifted by myself with a Canon EOS 40D with a 28-135 lens kit. What a piece of equipment! I'm very satisfied with it and I'm ordering a Macro Lens in a few... But before it I have a question. I've been trying to MACRO some stuff around here, yes, I know, the lens that come with the kit is not good for MACRO at all, but I like to insist, and after some tries I found my autofocus fighting for a decent focus when I was a little closer to the subject.

The point is, with no 100% sharp focus point from the autofocus the light that confirms that the focus have been locked blinks saying that the focus is not accurate and it doesn't allow me to take the picture. Is this behavior of not allowing you to take the picture making you use Manual Focus instead correct? I read the Manual on the sessions that says "When Autofocus fails" but it's not very clear for me in terms of behavior that the camera simply doesn't take the picture with the "messed" focus.

Thanks in advanced for your help and patience,

- c0rreia

Mike_Adams

Canon EF 70-200mm f/2.8L IS USM

02/05/2008 11:16:52 PM · #2

Well, I am not sure I fully understand the situation that you are dealing with so I will give you some thoughts and you probably will need to give some extra details to ensure the helpful posters here can give you some help. My first thought is that you are inside the near focusing distance. Easiest way to describe this would be if you were on the wrong side of your macro or the lens' range. Example (this is not the actual distance for your 28-135 as I currently my 70-200 on my 40d body) for my 70-200 the near distance is 1.5m. If I go inside that distance even in good lighting the 40d will fight for focus and the shutter will not fire. If you go to manual focus or if you back up it will fire all day long. Give that a try. However if what you are saying is that now you cannot focus at any distance and get a shutter release then post again with full camera settings and maybe we can get you to a place where you aren't stuck.

cpanaioti

Canon EF 70-300mm f/4.5-5.6 DO IS USM

02/05/2008 11:34:02 PM · #3

That usually happens when you are closer than the minimum focusing distance for the lens. For that lens you need to be at least 1.6m (or is that feet?) away from the subject.

It also happens when there is not enough contrast in the scene for it to lock focus.

Message edited by author 2008-02-05 23:41:15.

02/05/2008 11:38:56 PM · #4

Hello Mike,

Thanks for the quick reply and for the clarification. I think you got my question solved, it's was related to going beyond the range, the range of my 28-135 is 0.5m, I was going for about 0.25m and it wouldn't fire, you gave me the answer for that saying that the focus gets in trouble if you surpass the limit distance. The thing that was intriguing me was the fact that the camera wouldn't fire, I've never seen this before, but if you say that the behavior is the same for yours 40D, that reliefs me.

Sorry if I caused any misunderstanding in the explanation, English is not my mother language.

-

In time, thanks for cpanaioti for the reply too! :D

Regards from Brazil,

- c0rreia

Message edited by author 2008-02-05 23:40:14.

02/05/2008 11:58:21 PM · #5

When shooting macros, the best focus method is manual focus only, for two reasons:

1) To get the greatest magnification, you have to guarantee your camera is at minimum focus. So switch to manual, set it to minimum and don't let Auto Focus change it. Instead, move the camera itself back and forth to get the perfect focus.

2) Because macros images have such razor thin Depth of Field, the only way to guarantee that you're focusing on what you want, is to use manual focus.

02/05/2008 11:59:07 PM · #6

Que parte do Brasil? Estou querendo voltar para o Brasil em Maio. :-)

02/06/2008 12:16:40 AM · #7

Originally posted by dwterry:

Que parte do Brasil? Estou querendo voltar para o Brasil em Maio. :-)

Sou de Recife, onde o maior Carnaval do Mundo ferveu por esses dias.

AbraÃ§os!

Canon EF 24-105mm f/4.0L IS

02/06/2008 12:25:43 AM · #8

E nÃ£o tem fotos do Carnaval para mostrar?

Delta_6

Canon EOS-7D

02/06/2008 12:44:07 AM · #9

Feeling kind of locked out here, not terribly good.

Canon EF 70-200mm f/2.8L IS USM

02/06/2008 12:54:14 AM · #10

Sorry ... I miss Brazil and relish the opportunities to converse in portuguese. Should have done it via PM. My apologies.

Photologist

Apple iPhone 15 Pro Max

02/06/2008 12:57:49 AM · #11

Have you tried the magnifying focus feature of LiveView?

Bear_Music

Samsung Galaxy S24 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

02/06/2008 01:44:08 AM · #12

Originally posted by c0rreia:

The thing that was intriguing me was the fact that the camera wouldn't fire, I've never seen this before, but if you say that the behavior is the same for yours 40D, that reliefs me.

This is standard behavior for dSLR cameras, or at least the Canons. If focus won't lock, the camera won't shoot. When the camera is having a hard time focusing, switch to manual focus on the lens. For macro work, manual focus is the only way to go; you can't rely on autofocus to be where you want it to be.

R.

fotomann_forever

02/06/2008 02:15:34 AM · #13

Originally posted by Delta_6:

Feeling kind of locked out here, not terribly good.

LOL... have you not met babelfish? :-)

02/06/2008 10:03:41 AM · #14

Originally posted by fotomann_forever:

Originally posted by Delta_6:
Feeling kind of locked out here, not terribly good.

LOL... have you not met babelfish? :-)

Sorry for the portuguese, budies. It was just a homesick friend asking from which party of the country I am, I replied that I'm from the Northeast coast, land of the biggest Carnival in the world.

Unfortunately I didn't insured my camera yet, so I didn't risk it in the middle of the party.

Thanks again for all the help and replies.

:)

goc

Apple iPhone 4

02/06/2008 10:24:06 AM · #15

welcome, now go on and take some photos :-)

hihi

Tez

Canon EOS-5D Mark II

Canon EF 85mm f/1.8 USM

02/06/2008 10:38:35 AM · #16

switch your camera to manual and you can take pictures at any length from anything and the focus points won't matter.

I think that's what you were talking about.

garrywhite2

Canon EOS-7D