help with my 85mm 1.8

Hi everyone,
I feel dumb to have to ask this question but I'm having a hard time getting a feel for when to use what lens. I just got the 85mm 1.8. I also have a 17-85mm f4-5.6 (On a 350D) When I do family shots, of course I don't go that wide, but should I be getting a sharper image than if I use the zoom? I was pretty frustrated when the other day when I was at f8 and didn't have all 10 people in the shot in sharp focus. Also when I was practicing portaits, it was beautiful if I just wanted face or eyes sharp, but if I want the whole body in focus and the background blurred what would you do? I know this is stuff that I just need to practice a lot to perfect but are there any tips that you can give to give me a good starting point?

If some of those people are within minial focus distance that can cause some out of focus shots.

As for the blurred background, you can shoot as wide open as possible (f/1.8) and get decently close but not within the minimal focus distance.

Here's a DOF calculator, but DOF is probably not your problem - the 17-85 is just plain sfot in the corners. Something like 17-55 or tammy 17-50 would probably get better results:
http://www.tawbaware.c​om/maxlyons/calc.htm

I think the OP means he's shooting with the 85 f1.8 at f8.
distance from your subject to the background will effect the amount of blur you get, no?

dekalbSTEEL wrote in post #3315844
distance from your subject to the background will effect the amount of blur you get, no?

Precisely. I don't think it was mentionned whether the OP was shooting indoors or not - if he is, the 85mm might not allow enough working distance for reasonable DoF. On a crop body, 30/35mm is a better choice of FL for group shots. Keep in mind as well that DoF will be quite narrow at close distances with an 85mm, even at f/8.

I've used my 17-85 for indoor group shots with good results... as long as the lens is stopped down to f/8 - f/11, most of the softness/CA that plagues the 17-85 should dissapear.

Anytime I shoot groups, I try to shoot outside in the shade (but on a sunny day) I want help with the assumption that I am shooting 6-10 people @ 85mm on my prime. What aperature will get all of my group in sharp focus. Is f8 still too wide? Will I get sharper focus with the 85mm lens every time? I've been trying to use it anytime I can get far enough away to use it

Perhaps you can upload a picture with EXIF, a picture is worth a thousand posts.

Using the DOF calculator I referenced, if you shoot your subjects from a distance of 20 feet at 85mm and f/8, the depth of field will be 4 feet 10 inches. Assuming you arrange the group in 2 rows you should have just enough DOF to get the people in focus if they are 2' or less apart. Since the width of the shot would be 5' 3" at 20 feet and 85mm (also derived from the calculator I referenced), I would expect you would shoot from further back than 20', which guarantees you will get 2 rows of people in focus.

http://www.tawbaware.c​om/maxlyons/calc.htm

For your reference, for group shots of 6-10 people I use my 10-22, or 17-40 if there is more space available, and even then I often don't get everybody in focus at a reasonable f-stop.

Ideally, on a crop camera you shouldn't go beyond f/13, as diffraction starts to become noticeable. However, in emergencies you could go up to F/22, although I would stop at F/16, to be very honest, as sharpness disappears rather quickly. Beyond F/22, although theoretically DoF gets larger, because of diffraction a picture at F/32 on a crop body is going to display as if it has less DoF than the pic at F/22, and become generally fuzzy. And that is with a very good lens.

Kind regards, Wim

Try using your DOF preview button

Federkeil wrote in post #3315579
Hi everyone,
I feel dumb to have to ask this question but I'm having a hard time getting a feel for when to use what lens. I just got the 85mm 1.8. I also have a 17-85mm f4-5.6 (On a 350D) When I do family shots, of course I don't go that wide, but should I be getting a sharper image than if I use the zoom? I was pretty frustrated when the other day when I was at f8 and didn't have all 10 people in the shot in sharp focus. Also when I was practicing portaits, it was beautiful if I just wanted face or eyes sharp, but if I want the whole body in focus and the background blurred what would you do? I know this is stuff that I just need to practice a lot to perfect but are there any tips that you can give to give me a good starting point?

Firstly use tripod and take several pictures at each f stops (in my case more than 100 pictures) at outdoor, not indoor.
Secondly chech the pictures in detail through good monitor as possible as you could.
Lastly print big size like 8 x 10 and check.
If still under sharpness, got service or send to Canon for warrant service.