Take a look (soft focus on Rebel XT)

Barefoot and Natural · March 30, 2007

Hi everyone!!

I am not sure if this is the right forum for this but I will try and then if need be please move to the right spot!! Thanks!

I am wondering if there might be something wrong with my focus sensor with my Rebel XT.....I have had this come up before and now it is driving me crazy!!

Some shots are crystal clear and then some shots are soft.

Take a look at this gallery http://barefootandnatural.smugmug.com/gallery/1610491/1/137507357#137507357

Minus the first picture.....take a look at the photos and please give me some advice or tell me how to check too see if there is something wrong with my camera. I have no idea what my camera is focousing on!! When i look through the view finder...they seem to be perfect, BUT upon uploading, this is what I get!!!

All images shot with a 70-200 f/4 Canon Lens at different focal lengths and my camera was set to <P>

I very much welcome any advice.....nothing has been done to these images
so that you may see the exact shot. Also feel free to edit as necessary!!

Thank you all in advance!!

Heather

SitterS · March 30, 2007

Heather tried to take a look but it is hard for me to determine which ones in particular you are referring to. Maybe post one or two here to look at on the thread. One with good focus and the other where you feel the focus is off. Also EXIF data may be helpful to add.

Shane

Barefoot and Natural · March 30, 2007

Ok, here we go....

This one seems that the focus might be on the tree:

Cropped:

Thank you again!!!

Thanks so much for the quick response!!!!

Heather

Awais Yaqub · March 30, 2007

Very nice photos i like them

DoctorIt · March 30, 2007

Barefoot and Natural wrote:

Hi everyone!!

I am not sure if this is the right forum for this but I will try and then if need be please move to the right spot!! Thanks!

Hey Heather, I'm moving you over to cameras, where the gear-heads can help you with this issue, since that's what you're looking for rather than comments on the shots.

btw, I also added to your title, helps to tell people why they're "taking a look" (also down the road for searching, if anyone else with a rebel xt has this issue).

as for your issue, slight back-focus issues are not uncommon. if this really is persistent and reproducible, you may consider having the camera checked out by Canon.

Barefoot and Natural · March 30, 2007

DoctorIt wrote:

Hey Heather, I'm moving you over to cameras, where the gear-heads can help you with this issue, since that's what you're looking for rather than comments on the shots.

btw, I also added to your title, helps to tell people why they're "taking a look" (also down the road for searching, if anyone else with a rebel xt has this issue).

as for your issue, slight back-focus issues are not uncommon. if this really is persistent and reproducible, you may consider having the camera checked out by Canon.

Thank you....I appreciate the move and the update......I added a few more shots taken with two different lenses.

Some of the file names reflect the lens Example: Lucycrop-50 (used my nifty 50)
Or Example: Oreocrop2-70-200 ( used my 70-200 Canon Lens)

Thank you all for you help.....I am really at a stand still as to what might be happening!! More than likely......operator error (most of the time that is the case with me

)

Heather

Sam · March 30, 2007

I took a quick look at the 3rd photo on your site. (girl by tree). It's really hard to see anything with this small of a fife, but the white balance is off, and it looks like, (small file?) that it could accept more sharpening.

I had no idea these cameras had a "P" mode.

I recomend learning how to not use the "P" mode. Try having only the center focus point active, that will allow to control where the focus point is.

Sam

ziggy53 · March 30, 2007

Heather,

The EXIF is truncated, so I can't see your shooting mode, aperture or shutter speed.

Since you mentioned the mode was "P", can I assume you are letting the camera do most of the automation?

The first photo, little girl by tree, appears to be "back focussed" a little, and yes, I think prime focus is the tree. I am guessing that the texture of the tree is selected by the camera for focus, because the texture of the bark is an easy target for autofocus to "key" on. I bet the lens was set for f4, because of the relatively short DOF.

If you had used a single spot focus, and focussed right on the girls' eyes, I think you would have gotten the desired results. I would also recommend maybe ISO 200 and Aperture mode for this type of image, in open shade.

The next two images appear to be "front focussed". Again, I think the camera could not accurately choose the appropriate target for focus.

In the first case, the boys shirt seems the prime focus, and in the last image, I think the bucket in the foreground seems to have influenced the focus.

Single spot focus would probably be (or have been) beneficial for each of these type of images.

Manual focus might also work, but it's a pain on the XT without a focus aid like a viewfinder magnifier.

LiquidAir · March 30, 2007

The kinds of focus errors you are seeing here could be hard to detect through the viewfinder. I use a higher precision (but darker) ground glass for my view finder to help me see focus. That one is made by Canon for the 5D, I don't know what is available for the Rebels.

Some general advice for things to try when you are having trouble with accurate focus:

Set the camera to use the center focus point only.

The actual focus sensor is about twice as large as what you see in the viewfinder. Be careful of anything high contrast near the focus point because the camera might pick it up.

Focus points pick up the highest contrast edge in their view whether it is in the center of what they can see or on the edge. If there is a high contrast edge near what you want to focus on keep some space betwen the focus point and that edge even if that means not putting your desired focus location dead center in the rectangle.

AF is not as simple as you would have hoped. Try playing with your AF points and a thin branch against a distant background. See how far you need to move the AF point off the branch before the camera picks up the background. Try this against different backgrounds. Somtimes focusing on the branch is easy, other times it is hard.

colourbox · March 30, 2007

Definitely check your focusing technique before sending the lens in.

I shoot with an XT and I avoid the automatic focus point selection as much as possible. I prefer composing first and then using the manual focus point selection feature, using the wheel to pick the red focus point closest to the eye or other preferred subject, and making sure focus is locked on before pressing the shutter the rest of the way. I just don't trust the auto focus point selection especially when depth of field is so narrow. The times I've let it pick, it picks the wrong one too often.

You can also use the center point method, but I avoid it due to possible parallax-related issues that result in a different kind of slight focus error, which is again made worse when you have narrow depth of field. But if it's a high movement situation where I don't have time to use the wheel between shots, I will leave it on the center point.

LiquidAir · March 30, 2007

colourbox wrote:

You can also use the center point method, but I avoid it due to possible parallax-related issues that result in a different kind of slight focus error, which is again made worse when you have narrow depth of field. But if it's a high movement situation where I don't have time to use the wheel between shots, I will leave it on the center point.

I spent some time looking at this issue. There is a tradeoff using the outer focus points. On most Canon bodies, only the center focus point is a high accuracy cross-type sensor. The outer ones are lower accuracy linear ones (except 1-series bodies which usually have multiple cross sensors). Under most shooting situations I find I am better off using the more accurate center focus point and dealing with the paralax (in one way or another) than choosing a less accurate focus point because the paralax error is often smaller and always more predictable.

pathfinder · March 30, 2007

Using autofocus is not a simple as just pointing the camera at a subject and assuming the camera will choose the precise, correct focus point.

The AF system STRONGLY favors high contrast over low contrast, sharp linear lines over soft contours, and near targets over far targets. This is particularlytrue for Canon's consumer grade DSLRs.

This means when shooting portraits or people, in general, you need to 'ride herd' over the AF point used, and place it precisely over what you wish to be precisely focused. If you allow the camera to make this choice by it's selecting the AF point, it will be wrong much of the time. That is not a defect of the camera focusing system, but of user errror. In skillful hands, the accuracy of the AF system rises dramatically.

So learn to choose only one AF point in the frame and use it precisely- you get to choose which point for each frame. The center point is more sensitive, but Canon says it is not better to use it than the appropriate sensor for the shot. I try to use one and only one active AF sensor for each frane, unless I am shooting high speed action and then I stop down to get better Depth of Field.

Barefoot and Natural · April 1, 2007

Thank you everyone for you words of wisdom!!
I practiced a little more yesturday and I will be doing the same today as we are going to a 500,000 Easter Egg Hunt!! Get ready for some SHARP pictures of plastic eggs!!!:D:D

Really thanks, again....I changed my sensor to the center yesturday and gave it a wirl!! Better, but just does not seem to be consitant. I have aslo tried manual focus on still object with the same result.

I will contiue to practice practice pratice, try again, try again, try again!!

Thanks again you all......I new there was a great reason behind my registering!!!! You all are awesome!!

Heather

Jeffro · April 1, 2007

Barefoot and Natural wrote:

Thank you everyone for you words of wisdom!!
I practiced a little more yesturday and I will be doing the same today as we are going to a 500,000 Easter Egg Hunt!! Get ready for some SHARP pictures of plastic eggs!!!:D:D

Really thanks, again....I changed my sensor to the center yesturday and gave it a wirl!! Better, but just does not seem to be consitant. I have aslo tried manual focus on still object with the same result.

I will contiue to practice practice pratice, try again, try again, try again!!

Thanks again you all......I new there was a great reason behind my registering!!!! You all are awesome!!

Heather

If you are shooting still subjects and have the camera set to AI Servo, it will tend to look for movement.....which can cause your shots to be out of focus too. Sometimes we seem to think the camera is smart enough to do it all for us, but it isn't. We need to set the correct settings for the things we are shooting. And "P" mode....forget about it. Make the camera do what you want it to do, not the other way around.

Glenn NK · April 2, 2007

Jeffro wrote:

Sometimes we seem to think the camera is smart enough to do it all for us, but it isn't. We need to set the correct settings for the things we are shooting. And "P" mode....forget about it. Make the camera do what you want it to do, not the other way around.

Totally agree.

Try this - use the manual focus ring on the lens. You will soon see that focusing isn't that easy!!

You (and hopefully I) are smarter than the camera - if we have difficulty getting the focus correct, what chance does the camera have of always performing better. After all, I know what I want in focus, and even if I tell the camera, it doesn't listen.

One other point I learned from portrait photogs; always focus on the eyes.

pathfinder · April 2, 2007

Glenn NK wrote:

Totally agree.

Try this - use the manual focus ring on the lens. You will soon see that focusing isn't that easy!!

You (and hopefully I) are smarter than the camera - if we have difficulty getting the focus correct, what chance does the camera have of always performing better. After all, I know what I want in focus, and even if I tell the camera, it doesn't listen.

One other point I learned from portrait photogs; always focus on the eyes.

LiquidAir · April 2, 2007

Glenn NK wrote:

One other point I learned from portrait photogs; always focus on the eyes.

One thing I have discovered while shooting portriats with fast lenses is the focusing on the eyes is not always as simple as it sounds.

First, you need to pick the proper eye to focus on. Most potraits have a dominant eye and you should focus on that one. If the dominant eye is in focus most people won't be bothered by the other one being a hair soft.

Second, becareful about eyebrows. If you simply point the camera directly at the eye it will sometimes pick up eyebrow on people with dark hair because the eyebrow is closer to the camera. I generally point the AF at the top of the cheek rather than directly at the eye so that the eyebrow is safely outside the area of the AF sensor.

pathfinder · April 2, 2007

Yup, eyes and eyelashes, not eyebrows. Ya just gotta ride herd on those AF points and keep them in their proper place.:D

Barefoot and Natural · April 2, 2007

I am loving these tips....this is how my camera setting are set:

Quality: L (with the quater moon) I am not comfortable with RAW yet

Red-eye: On

AF Mode: One shot

Metering Mode: Circle with dot in it (not really sure what this is)

ISO speed: Changes due to the available light ( I know what this function does)

I did practice this weekend with an outting that we did and I posted some pics here: http://www.dgrin.com/showthread.php?t=57896

I was REALLY happy with the pictures of my son......now I was not in the perfect postition for full frontal face shots, but I was really happy the way his eyes were so sharp!! But I was taking it with my "nifty fifty" and I have always liked that lens...I thikn I got a really nice copy!!

I did shoot them in Manual Mode so I could learn to take more control of my camera and the dsired results.

I will continue to practice.....and will use this wonderful advice from all of you. Thank you all again......this forum is the best!! By far!!!

Heather

Barefoot and Natural · April 2, 2007

I will add one thing also.....I do "choose" my focus points and I usually go for the center one when photographing one person, but when I want to photograph let's say 3 people and you focus on the center person right? But is that were the DOF field comes in also? It can't be to shallow or else the "side" people with be out of focus right? Or should I let all the focus points be available?

Have I told you all lately how wonderful you are??:encore

Heather

claudermilk · April 3, 2007

Barefoot and Natural wrote:

Metering Mode: Circle with dot in it (not really sure what this is)

Check pg 77 of your manual--it's Evaluative Metering.

Sounds like you're getting it. For a group of people, that's basically the plan of attack I would have--and use the DOF preview button to verify I have enough to cover the group.

colourbox · April 3, 2007

Barefoot and Natural wrote:

I will add one thing also.....I do "choose" my focus points and I usually go for the center one when photographing one person, but when I want to photograph let's say 3 people and you focus on the center person right? But is that were the DOF field comes in also? It can't be to shallow or else the "side" people with be out of focus right? Or should I let all the focus points be available?

I would still choose a focus point. What you want to watch out for is the depth of the group. If it's 3 people all in a perpendicular line to you, that's not too hard because they are all about the same distance from the lens. If it's a few rows of people, you need enough depth of field to get the front and back rows in focus. If it's a single row but you're looking at them from an angle or the side, you need enough depth of field for the nearest and farthest persons. That last one is tricky when you don't have much light, because then you don't have much room for stopping down unless you have a tripod or maybe IS. At least with digital you can try hiking up the ISO.

Take a look (soft focus on Rebel XT)

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