Focusing issue

[lingaesh]

hi guys how r u, after long time. once agaim i came up with focusing issue, now i got one thing that the problem caused by my inaccurate focusing skill. i dont know where to focus in group photos, and which focus points should i use. SINGLE POIN OR ZONE MODE, OR ALL 19 POINTS. am using canon 70D. guys please make me sense. thanks in advance. ONE MORE THING IS AM SHOOTING IN RAW FORMAT.

[Manfred M]

Raw is neither here nor there and has no impact on focus.

Virtually all of my work is done using a single focus point that I will lock and then recompose to take the shot. That way I know where I am focusing and will apply an appropriate aperture to give me enough depth of field to ensure that all my subjects are sharp.

I find that the automated focus modes work well most of the time, but if there are a lot of things to focus on, the camera can choose the wrong ones.

[Black Pearl]

Post a shot you are having trouble with - indicate where on the image you focused, make sure you tell us what lens you were using and if its a zoom what focal length it was set at the aperture you used. This way we will have a good indication of what you're doing now and may be able to help by given more specific pointers.

[george013]

hi guys how r u, after long time. once agaim i came up with focusing issue, now i got one thing that the problem caused by my inaccurate focusing skill. i dont know where to focus in group photos, and which focus points should i use. SINGLE POIN OR ZONE MODE, OR ALL 19 POINTS. am using canon 70D. guys please make me sense. thanks in advance. ONE MORE THING IS AM SHOOTING IN RAW FORMAT.

1.
First off all is you should know what the camera does do. It adjusts the lens so that a plain parallel to the sensor is in focus. The distance to that plain is different from the distance to your subject. Unless it's in the middle of your viewfinder. There's only one plain that can be in focus.

2.
Sharpness is something subjective. One can say that if you see a printed point at a distance of an arm length as a point, it's sharp. Once you see it as a circle, it's unsharp. So that point is given a 2-dimensional size which results in changing the two dimensional plain in a 3-dimensional block. Adding a traject in front and after your plain which is said to be sharp.

3.
The different focus points help you to get a subject in focus not being in the centre. The result is always a single plain with different subjects in it.

4.
If you want to shoot a subject with a depth, so 3 dimensional, like a group, you have to take care that that in focus block has the right thickness, using the right aperture. That's where the dof calculator comes in.

5.
When you understand that there is something as a block which is in focus, then you can play with that. Focus on something in the middle of the group and some part of the space before and after it will be in focus. Look at the dof calculator for more specific data.

6.
You can set the camera so that you let the camera chooses the right focus point. That means you've to give the camera access to these focus points. Normaly used for dynamic subjects, birds etc.

Ther're more dofcalculators, also on this site.
http://www.dofmaster.com/dofjs.html


George

[Shadowman]

I would think aperture would be just as important depending on how the group is massed. Another thing to consider is the lighting on the group, is the group outdoors where light is possibly even or is the shot being taken indoors and you might need to use flash which can create bits of unevenness depending on how light is positioned?

[rpcrowe]

lingaesh...

Welcome to the Forum.

Regarding focus... It would really help if you posted a sample or two of your images with focus problems.

IMO, posting your problem images would help us to isolate focus error from an unsharp image resulting from a shutter speed too slow to stop camera shake...

Generally camera shake problems show up as a general lack of sharpness all over the frame while focusing error results in some areas sharp with other areas unsharp. When the areas (usually your subjects) that you want sharp are not, that is a problem...

Quite often problems with focus are increased when the lens is wide open for the shot. This often happens when the photographer elects to shoot using available light with the lens wide open. A wide open aperture often doesn't provide enough Depth Of Field (area from the closest to the furthest points of acceptable focus) to get a subject or group of subjects all in focus...

Shooting with an aperture of around f/8 to f/11 or so, will provide enough DOF to minimize, all but the most blatant focus errors. Of course, using a small aperture like that, indoors, usually requires some additional light. A hotshoe flash, used correctly (often bounced) will add to your ability to shoot with a smaller f/stop. Very adequate Canon hotshoe flashes can be had used on eBay from around $50 USD in the USA - it will help if you modify your profile to let us know where you are located. I have recently purchased a second Canon 420EX flash for less that $50 on eBay USA. I own several Canon hotshoe flashes ranging in price from a used 420EX at fifty bucks to a new 600EX RT at over three hundred dollars.

Here is a decent video on focusing with the Canon 70D...
https://www.youtube.com/watch?v=3vQwZzbhzXs

Generally, an image is sharpest from 1/3 in front of the distance focused on to 2/3 behind. Focusing 1/3 into the group might help if all the other parameters are set up correctly.

[Manfred M]

Generally, an image is sharpest from 1/3 in front of the distance focused on to 2/3 behind. Focusing 1/3 into the group might help if all the other parameters are set up correctly.

Richard I used to think that as being the case, until someone directed my to the article at a photo website called CambridgeInColour, where there is a nice table suggesting this is not quite the case. This is more or less correct at wider angles, but as the focal length increases it gets to be close to 1:1.

https://www.cambridgeincolour.com/tu...h-of-field.htm

[mikesan]

Virtually all of my work is done using a single focus point that I will lock and then recompose to take the shot. That way I know where I am focusing and will apply an appropriate aperture to give me enough depth of field to ensure that all my subjects are sharp.

I find that the automated focus modes work well most of the time, but if there are a lot of things to focus on, the camera can choose the wrong ones.

I too prefer to select and lock a single focus point; usually one of the center group cross type points for best accuracy. However this advice should come with a caveat: depending on the amount of 'adjustment' made to recompose the scene, the originally chosen object may no longer remain in focus. Adequate dof will guard against this error.

[rpcrowe]

Richard I used to think that as being the case, until someone directed my to the article at a photo website called CambridgeInColour, where there is a nice table suggesting this is not quite the case. This is more or less correct at wider angles, but as the focal length increases it gets to be close to 1:1.

https://www.cambridgeincolour.com/tu...h-of-field.htm

I stand corrected...

You are quite right but, the percentage of near versus far point of focus depends on focal length, distance focused on and f/stop - with the sensor format size thrown in for good measure...

I think that the 1/3 to 2/3 ratio is simply a truism that photographers might have accepted without researching. I know that I did...

As an example:

A Canon Crop camera using a 200mm lens at f/22 and focused at 100 feet will provide 34% in front of the subject with 66% to the rear. In line with the traditional 1/3 to 2/3 ratio...

The same camera/lens at f/4 and focused at 10 feet will provide a 50/50 split between near and far points.

A 50mm lens at f/5.6 focused at 10 feet will provide a 44-56% split but, focused at 20 feet will provide a 37-63% split.

So I will stop using the generalization of 1/3 - 2/3...

[Manfred M]

I too prefer to select and lock a single focus point; usually one of the center group cross type points for best accuracy. However this advice should come with a caveat: depending on the amount of 'adjustment' made to recompose the scene, the originally chosen object may no longer remain in focus. Adequate dof will guard against this error.

I totally agree Mike, so the focus point must be chosen with care and consideration of the factors you mention. Effectively, the focus point must be a reasonably good proxy for the area you want to have in focus. When I shoot people, I tend to use point focus on the eye nearest the camera, so the amount of movement is negligible. Landscapes are often focused at infinity (or perhaps at the hyperfocal distance). As I tend to shoot these at fairly conservative apertures - typically f/8 - f/11, it does not tend to be an issue either.

[lingaesh]

this shot was taken with canon 70d 18-135 IS stm. f5.6, 1/200s, focal length 18mm. i feel that the photo is not tack sharp, its like fuzzy. i used Auto 19 points focus mode.

1.please kindly explain how to use single focus point like this group photo, and where to focus. and then,
2. what is focus and recompose, and how to do. kindly make me sense. thanks in advance.

[george013]

this shot was taken with canon 70d 18-135 IS stm. f5.6, 1/200s, focal length 18mm. i feel that the photo is not tack sharp, its like fuzzy. i used Auto 19 points focus mode.

1.please kindly explain how to use single focus point like this group photo, and where to focus. and then,
2. what is focus and recompose, and how to do. kindly make me sense. thanks in advance.

Read my former post for the theoretical background.

And to know how to handle your camera download the manual in pdf http://gdlp01.c-wss.com/gds/4/030001..._Manual_EN.pdf and look at page 103

If you understand that, point 2 can be explained.

George

[lingaesh]

hi george thanks for ur reply. i know how to handle, but i asked where to point the focus for group photo to get entire photo sharp. i know some basic concepts of photography like DoF such as,

[george013]

hi george thanks for ur reply. i know how to handle, but i asked where to point the focus for group photo to get entire photo sharp. i know some basic concepts of photography like DoF such as,

No, you have some lack of knowledge. That's why you ask soemthing. Nothing wrong with that.

this shot was taken with canon 70d 18-135 IS stm. f5.6, 1/200s, focal length 18mm. i feel that the photo is not tack sharp, its like fuzzy. i used Auto 19 points focus mode.

Unless I don't know the Canon way, it says that you let the camera make the choice. From what I think, next page, 104, "selecting the af-point manually". That's what you've to do first.

George

[Manfred M]

Lingaesh - George is spot on with his analysis. This is not a focus problem per se, but rather a depth of field issue.

Your camera settings (aperture) are not adequate to get everything into sharp focus, regardless of the autofocus mode you use.

I would suggest you read the CiC tutorial on Depth of Field:

https://www.cambridgeincolour.com/tu...h-of-field.htm

[lingaesh]

Lingaesh - George is spot on with his analysis. This is not a focus problem per se, but rather a depth of field issue.

Your camera settings (aperture) are not adequate to get everything into sharp focus, regardless of the autofocus mode you use.

I would suggest you read the CiC tutorial on Depth of Field:

https://www.cambridgeincolour.com/tu...h-of-field.htm

thanks for ur replies guys, as per ur direction once again i gothrough the tuto

[Mike Buckley]

I think that the 1/3 to 2/3 ratio is simply a truism that photographers might have accepted without researching.

I'm reasonably confident that I learned it in a Kodak series of books when I first began using a camera in 1983. Considering the source, I didn't think I needed to research it to determine whether it was true.

[george013]

I'm reasonably confident that I learned it in a Kodak series of books when I first began using a camera in 1983. Considering the source, I didn't think I needed to research it to determine whether it was true.

If you take the dof-calculator http://www.dofmaster.com/dofjs.html and fill in lingaesh parameters, f5.6 18mm and I guess something as 3 meter distance you get a ratio of 1 to 100, 1% in front and 99% behind. Making aperture 1.8 you get 34 and 66. Just play with it.

George

[rpcrowe]

Perusing the DOF Master tables for an 18mm lens and viewing your image, I suspect that the lack of sharpness problem is not totally one of incorrect focus.

Here are some DOF calculations at f/5.6 for an 18mm focal length on a crop sensor camera.

5 feet
Depth of field
Near limit 3.33 ft
Far limit 9.99 ft
Total 6.66 ft

6 feet
Depth of field
Near limit 3.75 ft
Far limit 15 ft
Total 11.3 ft

7 feet
Depth of field
Near limit 4.11 ft
Far limit 23.5 ft
Total 19.4 ft

8 feet
Depth of field
Near limit 4.44 ft
Far limit 40.6 ft
Total 36.2 ft

9 feet
Depth of field
Near limit 4.73 ft
Far limit 93.8 ft
Total 89.1 ft

10 feet
Depth of field
Near limit 4.99 ft
Far limit Infinity
Total Infinite

With this great DOF, it would be pretty difficult to get an image OOF even if the focus was on the tray of food (nearest to the camera).

I suspect that one problem you are having in this image is flare from a light source of some type somewhere above the lady at image left. Flare will often make an image seem less than sharp...

[xpatUSA]

I suspect that one problem you are having in this image is flare from a light source of some type somewhere above the lady at image left. Flare will often make an image seem less than sharp...

I suspected that too, perhaps that white-washed wall reflecting the sun.

Additionally for Lingaesh:

The lens is said to be sharp in the middle but less so elsewhere:



With that veiling flare, there will be a loss of contrast (see lady's hair at left) in several areas of the image which can be fixed with "contrast by level details" in RawTherapee, added micro-contrast 5x5px and a dose of de-convolution sharpening:



With an IS lens to help, I too might gone for f/8 and stood further back (see Imatest's comment above about zoom setting).