dSLR AF issues - advice/help needed

07/13/2005 03:24:55 PM · #1

I shot a wedding last weekend and some of the pics are not sharp. I thought it might be camera shake, but have decided that it is inconsistent focus of my camera...or perhaps i'm stupid...either way, i am frustrated.

Rebel 300D. I have tried the Sigma 18-50 and Canon 50 1.8, same results.

If it is a nice bright environment, no problems. Both lenses are great. BUT since i want/need to shoot weddings, I need to get sharp facial pics of people. I cannot get consistent results...i have tried useing my flash in every mode possible and have verified the AF assist beam is working.

Any suggestions besides taking 2 or 3 shots to get a good one? Taking 2 or 3 shots times is not feasible (OK for formal shots/portraits,but not when foplks are waling down the aisle or the charge needs time to recharge).

I have lots of test shots..not sure if posting any would be helpful or not. Yes, i am useing narrow DOF/small aps, but have tried up to f6.3 without any improvement, and this is only low light conditions.

suemack

Canon EF 24-105mm f/4.0L IS

07/13/2005 03:37:34 PM · #2

Can you post some samples to show us plse. What mode are you working with the camera?

BobsterLobster

Fujifilm FinePix S3 Pro

Nikon AF-S DX NIKKOR 18-200mm f/3.5-5.6G ED VR II

07/13/2005 04:08:15 PM · #3

Take a photo of a ruler at an angle, check the focus point against what you focused on... you might have a backfocusing issue.

Nikon AF Nikkor 50mm f/1.8D

07/13/2005 04:36:42 PM · #4

bobster - did that. all a-ok.
mode - happens in M, A, T, P...

Perhaps because i am focusing on the face there is not enough contrast/ the camera says it has locked on focus...

could it be an ISO related something? Seems to happen at ISO 400 moreso than lower iso...have to test that theory.

Here are some samples, 100% crops, no PP, just cropped and saved at 80k or so for uploading...you tell me what you see.

Message edited by author 2005-07-13 16:38:58.

deapee

Kodak V803

07/13/2005 04:40:07 PM · #5

A couple of those look ok on focusing. The others, I don't know -- do you only have center AF point selected?

Nikon AF Nikkor 50mm f/1.8D

07/13/2005 04:54:45 PM · #6

Originally posted by deapee:

A couple of those look ok on focusing. The others, I don't know -- do you only have center AF point selected?

yeah, I posted good and bad. basically I was testing flash options in my (rather) dark garage so that on saturday should i get to shoot at the wedding i will be prepared. I have been PPing my images from 2 weeks ago and some are rather, umm, soft to say the least. I know those are my fault, so hence the practice.

Yes, center AF point only. These were all focused on the little person's face.

Otherwise I learned: Using flash in auto, camera in manual with LS works the best I think(brighter whiter results). Second choice is all on ettl and add in some FEC on the camera (again , M mode on camera for both - settings (Av and Tv did not change) I like the extra sparkle form the secondary flash on the metz, but i get the evil redeye that way. Direct flash has more oomph, seems to be slightly more accurate focus wise, but gives shadows. Not sure if a lumiquest soft box would do much good, but would like to try one and see. Putting tin foil on the back of the LS to direct more light forward gives a yellowy cast to the skin tones. Odd.

Old timers (pre-ettl days) seems to set the camera on f5.6 and direct flash at f8 (mostly for fill). have not tried that, but with all the electronics why go backwards?

The not so sharp focus is what is bothering me most though.

deapee

Kodak V803

07/13/2005 05:14:27 PM · #7

If you're really getting into shooting weddings, you should really look into different cameras...d70 or 20d come to mind...but get a new flash too ... are you still using that older one? I would imagine flashes have come a long way since then.

07/13/2005 09:44:57 PM · #8

Originally posted by deapee:

I have a Metz 54 MZ4 - the latest and greatest one.
I want to get a 20D, or better the replacement for it, but that will have to wait until I have booked some jobs (for financial as well as practical reasons (the wife...)). Until I can make money with my camera, it is a hobby and I have spend a ton this year already...hell, the pics below are shot with the Rebel ($779), Metz 54 & LS($340 used, $440 new) and Sigma 18-50 2.8 ($440 new ebay, $520 b&h) and of course a memory card ($30 after rebate) and a protech strap and grip strap ($44) - and that is not all i have bought this year, but jsut what i was using today. To be serious at weddings...i'd want a 20D ($1300) and canon 70-200 4L ($580), a second flash maybe and 4 Gb more of flash cards ($400) at least. that'd be $2300, plus probably a strap, a flash bracket...can always use a good tripod...other lenses perhaps...

it is nice to be able to open teh wallet and buy the newest/best stuff. Two things come to mind - it is the photographer that makes the image not the equipment and to be in a the photo business one must remember it is a business, and the less invested means a higher return and more profitability.

07/13/2005 09:47:18 PM · #9

Originally posted by BobsterLobster:

Take a photo of a ruler at an angle, check the focus point against what you focused on... you might have a backfocusing issue.

I've heard that this is actually a poor way to test. A better way is to set up something that you can shoot as a flat surface that has lots of contrast... I would suggest dominos :-)

07/13/2005 09:50:19 PM · #10

Originally posted by kyebosh:

Originally posted by BobsterLobster:
Take a photo of a ruler at an angle, check the focus point against what you focused on... you might have a backfocusing issue.

I've heard that this is actually a poor way to test. A better way is to set up something that you can shoot as a flat surface that has lots of contrast... I would suggest dominos :-)

I did the ruler thing..seemed good, but not totally satisfied. So i set up some boxes - beer case, noodles, etc. colorful, losts to focus on and detail to read, can be set square or at a 45 degree angle. In great light i had no probs...i guess i need to repeat the test under actuall shooting conditions (ISO 400, flash...)

Test shots to be posted later...

07/13/2005 09:53:04 PM · #11

If you're shooting at a close distance, with a fairly wide apeture, chances are you're getting a very narrow DOF, which you understand. The problem comes if you're handholding, especially if you're center focusing and recomposing. This can change the focal plane enough to make the photo OOF. I also found after I upgraded that the 300D is not accurate in low light, or even in moderate light. It does MUCH better if you assist it with something such as an led flashlight, a laser pointer, or the flash assist. Use a tripod, and I bet a lot of your problems will go away.

07/13/2005 10:06:37 PM · #12

I was trying at the wedding to keep the 1/focal length rule for shutter speed in effect and with a 18-50 lens that should not be difficult. My flash has the AF assist, and this shot

shows (to me anyway) that it works as this is a dark corner of the garage and it looks to be in focus.

One issue i noticed i had exposure wise at the wedding was the way i use AE lock...i am used to no flash, so aim at what you want, push the shutter 1/2 way, recompose and shoot...not good with a flash! I am retraining myself on that bit. The focus should stay locked...this was before i installed the undutchables hack. I have since installed it (wanted FEC mostly, but RAW in auto mode is kinda cool) and these shots ar with it. I now (in theory) have control ocer focus - one shot or not. The focus assist light should only work in one-shot focus mode..so i have now set the camera on that. perhaps the wedding shots were the camera sensing subject movement and going into Ai servo...i have had it happen.

The shots here are all at 50mm and 1/80. i tried 1/100 as well...distance was about 12 feet, infinity focus on the lens is 10 feet. Also, at the wider angles (18mm for exapmple) DOF at 12 feet at any aperture is kinda large. (7.48 to 30.4 feet according to this site's calculator

With my test at 50mm 3.2 i should have a DOF of 2.11 feet (11 to 13 ft).
perhaps it is camera shake after all...more testing later tonite...can't leave DPC...addicted...

07/13/2005 10:09:08 PM · #13

the rule, if you want to keep it accurate to the original, would be
1 / focal X 1.6 = shutter speed.

07/13/2005 10:23:53 PM · #14

Originally posted by kyebosh:

the rule, if you want to keep it accurate to the original, would be
1 / focal X 1.6 = shutter speed.

I have read that, and then others repudiate it...I have been able to hold it at 1/60 but with the big nasty flash on it it gets heavy and unbalanced. I also figure the flash shoudl freeze the subject, but I know that if very dependent on how much of the recorded light is from the flash...one can drag the shutter with a flash and get neat OOF effects.

Gotta go now...must test...is dark, good time. will try hand held and tripod.