Using XT to shoot through the side-view mirror of a car

[haunting_your_thoughts]

Hello all,<br><br>Yesterday I was in my car and using my Rebel XT to

shoot at some trees behind me. I was using a 100mm lens and each time

I shot... although the trees appeared crystal clear through the view-

finder, when I took the shot, they were blurry and lack any amount of

Detail. This happened with f2.0. When I used f8.0, the shots were

acceptable. So to test this out, I also tried shooting the branch of

a tree which appeared to be "in focus" through the view-finder, but

when I took the shot, it lacked detail.<br><br>Any idea on what was

the cause of the trees to be blurry when I took taht shot through the

side-view mirror of my car?<br><br> Any help will be greatly

appreciated.<br><br>Thank you.<br>Jake

[phule]

<< Any idea on what was the cause of the trees to be blurry when I took taht shot through the side-view mirror of my car? >>

 

You didn't have focus on the trees but instead the mirror?

[haunting_your_thoughts]

No... The focus was directly on the tree. I could not see any dusc specs on the mirror.

[jayhai]

there probably wasnt a great enough depth of field. 2.0 would allow a small depth of field,

8.0 a lot larger.

[jayhai]

here is a breif explanation.

 

http://www.azuswebworks.com/photography/dof.html

[jimstrutz]

Also, most 100mm lenses are far sharper at f/8 than they are at f/2.

[haunting_your_thoughts]

Yeah but then wouldnt my view-finder show that the trees are blurry also?

[byronlawrence]

witha a rebel xt... no.

 

:).

 

actually determining focus and DOF with the small viewfinder in my 20d is not so easy. so I can imagine that on the xt (which i hear has a smaller finder) this can only be worse.

 

aside from that, maybe your mirror was dirty? I know that that can have a greater affect than you realize if the mirror is not so clean.. also, how much light is there when you do this. and what ISO are you using, you should be trying to use a fairly fast shutter speed to get a good image. if the focus is off even just a bit at larger apertures the effect can be pretty noticeable.

 

anyway those are a few thoughts on possible problems.

[rob_murray]

Maybe turn the car around so you wont have to use the mirror?

Maybe get out of the car even. Is this a joke?

[henrik.ploug]

If you show us the picture and the exif-data, it would be easyer to guess, what went wrong.

[haunting_your_thoughts]

Look Genious, I would have turned my car around if I wanted to. I was experimenting with shooting through a side-view mirror of the car. Maybe you should try it sometime. Photography is sometimes about perception from a different eye than your own. No, it's not a joke and perhaps someone tries this with their own car and see if the images come out clear, I would greatly appreciate it.

[jimstrutz]

I'm with you Jake, I shoot through car mirror sometimes too. Interesting view.

 

Other than DoF issues and not being all that sharp wide open, I don't know what would cause this. BTW, the Canon 100 f/2 isn't *that* sharp wide open. It's pretty good, but it sharpens up by stopping down. But since you have the lens, I'm sure you knew this.

 

What you might want to do is repeat the experiment with the mirror, and then get out of the car & shoot direct, at both f/2.8 & f/8. That would remove any doubts about the issue being anything other than the mirror.

 

And another thing. If the degredation of image quality was due to dirt on the mirror, wouldn't stopping down make it *more* appearant?

[haunting_your_thoughts]

Thanks Jim, I appreciate your help. Do you think my lns might be a bad copy? If it performs soft at f2.0 then wouldnt it also be true when I see through the view finder that things will appear blurry? The images I've taken... well... While I look through the viewfinder seems acceptable and clear to the point where I can see individual leaves, but when I shoot the picture and zoom in.the picture looks horribly blurry. I normally dont shoot at f8.0 but decided to give that a try and my image was still blurry, but not as much as f2.0. I am going to be performing an off-focus possibility test on my Camera today. Hopefully that will clear up the off-focus issue. If not, I will have to send it in to Canon for a lens replacement. I wish I had known about the soft aspect of the Canon 100mm f2.0 at f2.0. If I did, i would have got the 135 f2.0 L. :-(

[jimstrutz]

Not having seen your pics I wouldn't know if your lens is defective or not. I think that would be rare though as the Canon 100 f/2 is well regarded by just about everybody. I do know that pixel peeping at 100% makes just about every lens look marginal. Part of that is the design of the 20D with it's built in blur filter over the sensor to reduce moire patterns.

 

As far as the 135 f/2L being sharper wide open, I wouldn't know about that either as I've never used one. But just about every large aperture lens gets better/sharper when stopped down a bit. It's just the nature of the beast. There are some expensive exceptions to this though.

 

I don't find the 20D's viewfinder bright enough, big enough, or sharp enough to make good decisions about lens sharpness. It's not even good for determining if things are in focus. In fact, even a full frame camera with a really great viewfinder would not be able to do this well.

 

Some lenses do front or back focus on the 20D, so that would be a good thing to test. If that's a problem, it would explain why things are so blurry wide open. Stopping down would largely cover up the focusing error.

[d_mcn]

Ever stood in front of a "funny mirror" at a circus? The distortion is created by the fact the mirror is not perfectly flat. Even when you stand in front of your bathroom mirror, the glass isn't perfectly flat -- but for the human eye it's unnoticeable. A camera lens, however, will pick up and magnify ANY optical distortion and send it to the sensor.

 

The side mirror of a car is not PERFECTLY flat. It's unlikely you would ever get the same quality of image in ANY mirror...that you would get pointing directly at the subject.