Focus problem at f1,4

[henrik.ploug]

I have a Canon EOS 350D camera and a Canon 50mm f1,4 lens. I like to

use it in low light situations without flash, but I'm having problems

getting sharp images. The lens is sharp, so that's not the problem.

 

When I first got the camera it had all 7 focus points turned on. I

like to shoot pictures with an unsharp foreground and with the main

subject (usually a person) off the center. Therefore I turned off all

the focus points except the one in the center. When I shoot, I aim at

the persons nearest eye and then recompose.

 

My problem is that, when I recompose, the eye is no longer in focus.

This is because the plane of focus move with the axis of the lens.

And with the shallow depht of field at f1,4 I can't move it very

much, before the eye is unsharp.

 

I have tried selecting one of the other focus points without

recomposing, but I think that it takes to long time, and that the

spontanity of the picture disappear, before I have chosen the correct

focus point.

 

I have also tried using a different apparture (f2,8), but in really

low light, the shutter speed gets to slow and the pictures get blurry

because of motion blur. The ISO is already set at 1600, so I can't

increase it to get more speed.

 

Finally I have tried using flash (and f2,8), but find the light

unattractive and obtrusive.

 

Have anybody else had this problem, and do you know how to solve it?

[digitmstr]

Focus & recompose doesn't work. There are hundreds of posts on this subject.

 

Thinks about it for a sec.: The DOF a f/1.4 is alredy infinitesimal. If you focus as off-center subject with your center AF point you'd be rotating around your axis by certain number of degrees necessary to reach the subject with the central AF point. Once you go back to your desired shooting poistion the angle between the subject and sensor will have changed by the same number as well as the distance will now be different, as a result. Therefore, OOF picture...

[gilou]

On my EOS1N I focus (push the button half way) with the centre focus point and recompose and then press completely ! and it works well ....

 

Are you in AI Servo ? If So, deselect that !

 

Otherwise : MANUAL FOCUS !

 

hope this will help.

[jbq]

When you recompose, the focusing distance change. Avoid recomposing, or if you do keep the recomposing to a minimum.

[ky2]

Giampi, allow me to improve your claim:

 

"The probability for a sharp "Focus and Recompose" shot is inversely proportional to DOF."

 

I use F&R all the time. And yes, it works, within the above-limitation.

[mark u]

If you know you are going to be taking portraits it makes sense to select an appropriate focus point in advance. The camera can be set to keep using the same focus point from one picture to the next. Another thing to watch for is that it seem that AF works best with a very fast lens when focus is coming from too close rather than too far away. Try leaning forward, focussing once, then back to your shooting position and focussing again, or using the FTM feature of the lens (but be aware that FTM is not long term robust with the 50 f/1.4).

 

To use flash, you need to do two things: adjust the colour temperature of the flash to match more closely that of the ambient light by using a warming gel filter or a suitably coloured reflector; and diffuse it by reflection/bounce or the use of a soft box. It probably helps to dial down flash exposure compensation in low light as well. You'll almost certainly need to get the flash off camera - at a minimum with an offshoe cord, and perhaps using an ST-E2 to control it.

[digitmstr]

Ok - to be precise: focus and recompose involves a movement of the camera, usually around its (the photographer's) axis. However large or small this movement depends on the situation, photographer, etc... However, no matter what, the resulting problems will be a change in the angle between subject and sensor/film plane as well as a change in distance. A smaller aperture may MASK this side effect but, the problem doesn't change. Also, while we are talking details, it is important to note that increasing the DOF is NOT substitution for a properly set point of focus.

 

At f/1.4 the DOF is so small that ANY minimal shift/movement WILL produce an OOF image. I think it's best manually set an AF point that suits the situation.

[paul_chilton2]

Henrik,

 

try here: http://visual-vacations.com/Photography/focus-recompose_sucks.htm

[henrik.ploug]

I'm avare of the problem described in the article "Why Focus-Recompose Sucks", but I just haven't found a bettet method. I use glasses, and when I try to focus manually with the small viewfinder on the 350D, I get even worse results, than when I focus and recompose.

 

I appreciate Marks advice "to select an appropriate focus point in advance". But I was at a wedding resently (in a tent at night with neonlight) and I wanted some some shots of people talking, laughing etc. Some of the pictures were oriented like "landscape" and others were oriented like "portraits". So it was not possible to select a focus point, that I could use for all of the pictures. And people didn't wait for me to chose focus point from picture to picture.

 

I have considered bying a flash and the ST-E2 to make flash-photography a little more appealing. But like Giampi say - I still have to focus properly.

 

What do you do in low light situations?

[robert_nancarrow]

As Gilles said, make sure you're not in servo mode when you're shooting before heeding all the other advice given here, if you are then the lens will continue to focus on whatever it's pointed at, regardless (with) of your finger on the shutter release. It is changed with the little button near the shutter release and LCD panel and the lower right hand side of the panel indicates which focus mode you are in. Bob.

[henrik.ploug]

I'm not in servo mode. And I have configured the camera so that I can focus with my thumb on one button and take the picture with my index-finger on another button.

[digitmstr]

>>So it was not possible to select a focus point, that I could use for all of the pictures.<<

 

I am NOT familiar with your camera. On my 10D I can select any one of AF points as the HOME AF point so, I can return to it with ONE button press. In you case, you could have the home point set for one of the outside AF sensor which would work for vertical/portrait framing as well as off-center, landscape orientation.

[dogbert]

This is probably a stupid thought, but with digital, microchip controlled cameras these days, why doesn't someone invent automatic focus bracketing. It could be that hard.

[david_mazeau1]

I see you say, "this lens is sharp", and at F/8 or so, it sure is,

but look at the bottom of this page:

 

http://www.dpreview.com/reviews/canoneos300d/page16.asp

 

See how very different f/1.4 is than f/8 ?

 

Even if everything goes great, it's not super sharp at f/1.4 ... that's

my opinion.

[bens]

i thought 1.4 was relatively worthless to me because of the shallow depth of field, until i took photos of a very dark scene of a play from about forty feet away at 1.4. in that case it was a lifesaver, and the photos were fairly sharp btw. so i have concluded any issues i have are really with the dof, not the lens' sharpness particularly.

[henrik.ploug]

To Giambi

 

The 350D has seven focus points: One at the top, five in a row in the middle and one at the bottom. If I have selected the middle focus point and want to change it to the fifth focus point to the right, I have to push one button once to select focus-point-changing and another button twice to select the fifth focus point to the right.

 

If I then (for my next shot) want to select the first focus-point, I have to push one button to select focus-point-changing and then one button four (!) times to select the first (and left) focus point.

 

I have read the manual, but haven't found any descriptions of a HOME AF point.

 

If should use only one focus point for all my of-center-subjects it would probably be the fifth (in the center row to the right). That would be usefull for most "portrait" pictures, when I?m tilting the camera 90 degrees.

 

But if I want to shoot a "landscape" portrait with the subject in the left side of the image, I would have to turn the camera upside-down.

 

I have thought about another "solution" to my problem. I could shoot all my pictures with the main subject in the middle, and then crop the photos, when I got home. But that would be a waste of pixels, I think.

 

Thanks for all your advice. I may be a difficult costumer, but I appreciate your efforts.

[dogbert]

Henrik

 

On the 350D, it is quicker to use the command dial to select focus points than use the buttons. ie push focus point select button, then spin the dial.

[henrik.ploug]

To Geoff Francis: Next time I will try the command dial to select the focus point.

 

To David Mazeau: I must admit, that the lens look soft at f1,4 in the link you gave me. And I'm sure that it will be sharper, when I stop it down. But take a look at these pictures, which I just found at PBase. They are all taken at f1,4 with the Canon 50mm, and to me they look resonable sharp:

 

http://www.pbase.com/image/40694194

 

http://www.pbase.com/image/36369567

 

http://www.pbase.com/image/27954823

 

http://www.pbase.com/image/40778759

[brad_w]

Focus-lock-recompose DOES work the vast vast vast majority of the time and there are

millions, probably billions, of sharp photos in the world to prove it. (I myself have several

tens of thousands.) When tolerances are tight (close focal distance, large aperture) there

are issues to be addressed, but then, that's life.

 

Henrik, what noone else is acknowledging is that yes, it is a problem an there is no perfect

solution. Consider focussing manually or familiarizing yourself with the camera so that

moving the AF point becomes 2nd nature. Be aware the the one-dial interface of the 350D

is working against you in this regard. My apologies for my non-answer, but I think

practice is what you need here more than advice. Sorry :( -b

[brad_w]

Meant to add for Geoff:

Contax made a camera with AF bracketing, it turned out to be one of those great ideas that

was totally ignored by history. -b

[david_mazeau1]

I agree those images look okay too... pretty much. But they aren't

full resolution images, so I would say it's easier to not see the

problems in them.

 

The link I had there is too Phil Askey's tests, and Phil is quite

respected. I don't think he would have a bad lens or a faulty test

there. I trust him and the images he has as representing the

way things are.

 

And then lastly, no flash is allowed at the Louvre in Paris, so I

have taken quite a few pictures of art at 50mm f/1.4 ... and this

was my experience as well. This lens is never tack sharp wide

open.

 

The 135mm f/2 L is different. That lens is almost as good wide open

as it is at f/8.

[henrik.ploug]

To David Mazeau

 

I agree that dpreview.com is a reliable source. But firstly there will always be differences in the quality of different lenses. And secondly, what he is doing in the link is surely "pixelpeeping". Normally you wouldn't look at a photo that way.

 

But that being said your link has surely made me reconsider taking photos at f1,4 with the 50mm.

[dogbert]

"But that being said your link has surely made me reconsider taking photos at f1,4 with the 50mm."

 

If a picture looks good to your eyes, it is a good picture. Don't let anyone imply "well even though it looks good, it can't be becuase it was shot at f1.4". All that counts is the final results.

 

Brad was the Contax a film camera? It probaly makes less sense to have focus bracketing with film, whereas with digital the extra shots are free.

[henrik.ploug]

"If a picture looks good to your eyes, it is a good picture... All that counts is the final results."

 

I agree.

 

When I said, that I would reconsider, I meant that I would do some test with my 50mm wide open on a brick wall or something controllable to see:

 

1. How sharp is my lens really at f1,4, compared to the other apartures.

2. How close can I stand to the wall when I focus on an edge, recompose and take a picture, that is still sharp at the edge.

 

Even though it is pixelpeeping, it would give me an idea of what the lens is capable of, and in which situations I can focus and recompose.