Two stupid questions.

[HankScorpio]

(despite the fact that I was once told that there are no such things as stupid questions, only stupid people)

While pondering the universe at work today, I came up with two questions....

If you're photographing your subject in a mirror, is the distance to subject to the mirror or to the subject itself?
If it was the subject, you could get around minimum focusing distances by strategic placing of mirrors.

I've had two cameras that took CF cards and both remarked in the manual that the card would go in in what appeared to be the wrong way, ie label facing away from you. Now, why didn't they either, design the recepticle for the card the other way round, or if this is commonplace, put the labels on the opposite sides of all the cards?

Interested in the first one, curious but not interested in the second.

[V6GTO]

I think you have too much time on your hands...you should try working harder!

Martin.

[simpo two]

HankScorpio said:

If you're photographing your subject in a mirror, is the distance to subject to the mirror or to the subject itself? If it was the subject, you could get around minimum focusing distances by strategic placing of mirrors.

Depends if you want the mirror or you in focus. If it's you, you still need to retain minimum focusing distance from camera to subject via mirror. The mirror will be at less than that distance, but that's not really relevant.

I don't know if the AF would focus on the glass though.

Watch this space for a very close reversed photo of Hank's nose...

[te51cle]

In answer to your first question, you'll need to focus on the subject in the mirror. Just had to try this myself to be sure. I stood directly in front of a mirror. I focussed on the edge of the frame and found I was 1.5m away. I then pointed the lens at my image in the mirror and had to focus the lens at 3m to get myself sharp. I suspect there's some complex trigonometry involved in calculating the point of focus when you're at an angle as I tried to focus on an object at 45 degrees to me and the numbers didn't add up and I don't want to be calculating squares of hypotenuses at this time of night.

The second question is digital and I ain't got one of them fancy new fangled machines yet - will have by the end of the year I'm sure though !

[simpo two]

te51cle said:

I suspect there's some complex trigonometry involved in calculating the point of focus when you're at an angle as I tried to focus on an object at 45 degrees to me

Nope, just imagine a line from the lens, off the mirror and going to the subject - like a snooker ball bouncing off the edge rubber. The mirror just changes the angle, not the distance.

[V6GTO]

If you take a picture the camera captures the reflected light from any given subject. If you take a shot of yourself in a mirror the light leaves your body/clothes, travels to the mirror then comes back near enough the same distance. Your focusing distance is the length of the light travelled. There...clear as mud!

Martin.

[te51cle]

I've been up too late over the last few nights playing racing drivers on my PC - C3 Corvettes are a right pig to drive around corners !

After trying out with 4 different lenses and 2 different cameras I just realised that my measurements at a 45 degree angle were complete b*ll*cks as I'd swung around in my seat and moved the camera a couple of feet instead of rotating it about the film plane and taking the measurement correctly. Classic error. I will now fill in my application to be the designer for the Hubble Space Telescope replacement and go to bed !