Help, i have not got a clue on this one

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Teaboy

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Hi Guys,

This is going to sound incredibly stupid but i am pulling my hair out as to what im doing wrong.
First my set up i was using Canon 7d F2.8 L 70 - 200mm and a cheap ebay polorising filter.
I was trying to take photos of the Rally cars in wales yesterday and no matter what i did i could not get the shots in focus. Every shot is just out of focus and in the end i just kept my finger on the button hopeing one out of the sequence would come right.

I had the AF set on servo mode.

Many thanks for putting up with this obvious idiot question.

Cheers

Rich
 
What metering mode were you using? Single point or multiple? Auto or manual focus? Shutter speed?
Also, why spend that sort of cash on a decent body and lens then put a cheap crappy filter on the end. This may have been the problem.

Some images with exif data will help.
 
what camera mode were you on? what settings?

How much of the photo was in focus? it might be a dof problem due to fast shutter speed and a large aperture.
 
Thanks for the replys, i will answer as many of the questions as i can but i kept flitting on the settings tryiong to get a good photo.

Reason for carp filter was that it was in a box of crap i got given and i though any filter better than no filter where rally cars and stones are around.

I tried both single point and multi point focusing and there did not seem to be any difference.

Shutter speed betwwen 1/250 and 1/1000 again tried most of them.

Hands were so cold i could not get the filter unscrewed so only tried with it on.

Camera mode was TV, auto white balance.

Thats about what i can remember. I hope it is the filter as it is an expensive problem with the lens maybe. Having now looked at the pics the focus is worse the further away and all the photos apear to be missing colout they look very flat.

Cheers

Rich
 
Bad filters can do serious harm to IQ and the effect is worse at longer focal lengths. If you use a linear polariser instead of a circular polariser then that can actually b****r up the AF as well (not permanently, just while fitted). If you want to troubleshoot you really should get that filter off the lens and go back to basics - static subject, good light, tripod if poss and see how you do. There is much that could be wrong, but with that filter in the equation you might have a hard job pinning it down. Of course, the filter might actually be OK, but "cheap eBay filter" does lead one to point the finger at the filter in the first instance.

Of course, poor technique or unsuitable shutter speed can lead to shake/blur, which might be mistaken for poor focus. There's lots to ponder. I'd still take the filter off and see where you stand to begin with.
 
Teaboy said:
Hands were so cold i could not get the filter unscrewed so only tried with it on.

Having now looked at the pics the focus is worse the further away

Rich
Click to expand...

ring ring ring is that an alarm bell I hear :D

Camera (person stood around freezing his nuts off) shake comes to mind. Post up some pics as the crystal ball is in the cleaners ;)
 
Fast shutter speed + f/2.8 = shallow depth of field.

What ISO are you using? You may need to turn it up to keep a longer depth of field. Camera shake may of given a slight delay to focusing and so car is slightly nearer and out of focus.

You may find it better to use aperture mode to choose the depth of field and keep it in focus and change the ISO setting to keep the shutter speed high.
 
I dont think it was not camera shake as i tried my spare lens i had with me a cheaper 18 - 200mm and this worked fine. I changed iso through the day from memory 800 ish in the morning down to 400 ish in the afternoon. Will get some pics up when i can get at my flikr.

Cheers

Rich
 
I'll take a punt and say it is the polarising filter. Cheap polarisers are fatal on longer lenses - nothing to do with the linear/circular bit, just the poor grade polarising foil which gets magnified with focal length.

Polarisers are good for saloon car racing as the angles are just right to cut reflections from the windscreen, as it has done there. I use a Hoya HD CPL on my 70-200 with no sharpness issues, and the fact that it loses about 2/3rds of a stop less light than other polarisers is particularly handy when you need higher shutter speeds.
 
Its just lost its sharpness rather than being out of focus, i would say filter.
 
Was there any particular reason why you were using a polarising filter at all, apart from protecting the lens? They're not designed for this. Try a good UV or clear protection filter if this is what you want.
 
Thanks for all the help guys. The only reason that that filter was used it was the only one to hand as this was the first time out with this lens. Filter now in bin and getting a Hoya set ready for the next rally.

Cheers

Rich
 
Teaboy said:
Thanks for all the help guys. The only reason that that filter was used it was the only one to hand as this was the first time out with this lens. Filter now in bin and getting a Hoya set ready for the next rally.

Cheers

Rich
Click to expand...

Did you try some shots at home without the filter ??

Did it solve the problem ??

Hopefully it did and you've got everything sorted now...


Which Hoya filter are you getting ?
 
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