question about sharpness. - DPChallenge Forums

Nikon AF-S NIKKOR 24-70mm f/2.8G ED

11/23/2007 05:50:45 AM · #1

hi!
I have a (perhaps stupid) question. what exactly is responsible for the sharpness and the autofocus (except me)? the camera or the lens?? I sometimes take photos in theatre, but I have problems with the sharpness of the photos very often. I am using a Canon EOS 20 D and Sigma 70-200 mm, f 2,8 and Sigma 28-70 2.8-4.0!
hope anybody can help....please....

hotpasta

Nikon D800

11/23/2007 05:57:22 AM · #2

If people are moving, even slightly, if your shutter speed isn't fast enough (say 1/200 at least) there will be blurring. I have taken many LIVE images in concerts and what I do is use a monopod for stability. I try to keep my ISO at 800 as anything over this looks a little noisy. I then use manual settings with a wide open aperture for maximum light and the fastest shutter speed I can get for a good exposure.

Usually, if the lighting is good, it can be around 1/200, 1/250. If lighting is bad, I keep the exposure the same and up the ISO to 1100 or 1600.

The blur is usually movement from the people. OR, perhaps you are using a very slow shutter speed that your camera is selecting bacause of the low light.

I have the same lens as you, and if you look in my portfolio, you will see a handhels image of James Morrison, trumpet player, and maybe a few other live shots.

I am often called upon to be the photographer at our large church conferences, and I must admit, our lighting is superb and concert stadium quality, so I am spoilt!

Try some manual focus as well...

Tez

Canon EF 85mm f/1.8 USM

11/23/2007 06:00:08 AM · #3

The lens mainly, but it depends on other factors too. For example, if you autofocus with the shutter half way down, then wait for a bit, there is enough time for the subject to move away from where you were focusing- it could just be an inch, but it will make a difference.

Also, the in camera settings have an influence too: every camera has an anti-alias filter that kicks in when JPEG compression occurs, in some models this is responsible for softening some pics. You can get around this by raising the sharpness in the camera's menu settings, or just shooting in raw.

Back to the lens: every lens is at it's best when it's stepped down a few stops. My F2.8 is at it's best at F4 or F4.5, my 1.8 is at it's most awesome at around F5, but is still damned good before that.

Your lenses are pretty good but have a play with the camera settings, the aperture and try a few raw files and see if that makes an improvement. And focus and shoot straight away, don't focus, then wait for a bit. Do them as close together as possible to minimise the chances. You can get away with it to some extent if you shoot at F8, but in a theatre there may not be sufficient light to shoot at this aperture without raising the ISO to silly levels.

I shoot wrestling shows at ringside pretty often, and that has terrible lighting. I use my 17-50mm lens at F2.8 at ISO 800 and set the camera to AI Servo and select the centre AF point too, then i can track the subject in the centre of the frame and the AI focus constantly shifts itself for the best lock, to hopefully get the sharpest shot. Then I fire off multiple frames and see what I get. Also, I underexpose by about 1 stop to speed up the shutter even more and to make it look better, this gets me shutter speeds of up to 1/125 if there in a good spot, but I can get away with 1/50th and it still looks great.

Message edited by author 2007-11-23 06:02:14.

Nikon AF-S NIKKOR 24-70mm f/2.8G ED

11/23/2007 06:03:31 AM · #4

hi enzo! thanks for your answer, I know about shutterspeed and all that, but that's not the problem...unfortunately... it's really about the autofocus. for example if there's something behind the person with more contrast, or if there is light from behind the person, I just don't get the face sharp, because the autofocus concentrates on the better contrast and not on the part I (!) would like the be sharp.... I don't know how to change that...I already thought about saving up money for another camera... I just don't know whose problem it is - the camera's or the lenses.

hotpasta

Nikon D800

11/23/2007 06:07:45 AM · #5

Originally posted by Isi79:

How about manual focus, or I am sure you might have some autofocus settings that will work in the conditions. I am not sure which one I use, but I actually select the area of the frame I want the focus to be, and the cmera locks into that. I can shift it with the command dial at the back of my camera to suit the image, but I am not sure how you do that on the 20D...I am sure you can though.

Would your answer be to either go manual, or have a selected focus area that you tell the camera to focus on???

Tez

Canon EF 85mm f/1.8 USM

11/23/2007 06:08:20 AM · #6

That sounds like metering modes. Or, manually select the AF point you want and go from there.

11/23/2007 06:16:30 AM · #7

hi tez, thanks for your answer! Yes, there's never enough light. I was at a rehearsal for the press on monday, shot with 1600, and the aperture was about 2.8 most of the time, in some scenes the pictures were completely dark. with the -200 lens I need about 640 (?) shutter speed, because it is really heavy. so there's no chance to have aperture 5.6 or even 8 most of the time...
Though I never used AI servo, that's a good idea, and use center AF. thanks for that.

enzo: yes, I've tried manual focus, and I do this in rather "quiet" scenes, and it works, they are are sharper than the ones with autofocus, but I take pictures in musicals, so if they are dancing it's useless to try that...
yes, I can choose the area where the autofocus should be. but I can't change that for every single picture when I'm shooting in a show....until now I've chosen the setting with the most points, I thought that would be best, but perhaps this was my mistake, obviously...

Tez

Canon EF 85mm f/1.8 USM

11/23/2007 06:38:13 AM · #8

the most points is fine, it just depends which points it is picking up, if it's getting the stage and not the performers, then what's the point?

What shutter speed are you getting now? I think at 1/100th you'll be alright except during the most lively performances.

Canon EF-S 18-55mm f/3.5-5.6 II

11/23/2007 07:08:06 AM · #9

hm, yes, I will try center AF, I'll see if that works when I take pictures of a show the next time.
1/100 th???? I can't hold that, and if they are moving it won't be sharp too. but I think I'll get a monopod too, as enzo said.

surfdabbler

Canon EOS-5D

11/23/2007 07:11:16 AM · #10

I've done some photography under stage lights, and yes, it's pushing the limits in the low light. It was before I got my Sigma 70-200 2.8, so I had a borrowed 75-300 4-5.6. I was aiming for 1/60th shutter speed most of the time. Any faster than 1/120th, and I'd start thinking about closing the aperture or dropping the ISO, as this will give a nicer shot.

Definitely use a tripod so you don't have to worry about camera movement. In that sort of light on a long lens, you are going to get camera shake without a tripod. No way around that.

I'd agree with centre spot focus only. Forget about composing shots artistically. Subject bang in the centre and centre spot focus. Particularly in dramatic scenes, a lot of the stage can be dark, and if your spots don't find anything light, they won't focus. If you want rule of 3rds or offset composition, then shoot wide and crop later.