Mirror focus

[NicolaB]

Is it possible to get perfect focus using a mirror? Does the quality of the mirror itself come into play?????

I set my focus on the eyes of the littles ones reflection in the mirror using auto focus.

I know the focus is not bad - but it is not as perfect as it would have been on her. (I have just noticed the shutter speed was very low - guess that could be it, but the questions still stands?)





Camera Canon EOS 5D Mark II
Exposure 0.02 sec (1/50)
Aperture f/8.0
Focal Length 85 mm
ISO Speed 3200

[SusanH1970]

It actually looks like a combination of camera shake due to a slow shutter speed, motion blur, and it appears that the focus fell on her left hand. I've seen plenty of mirror shots where the subject's eyes are in perfect focus, so I doubt it's an issue with the mirror.

[inkista]

Um... why were you at f/8? Shooting with the 85/1.8, you had plenty of aperture to spare. If you'd opened up to f/4, you could have lowered the iso to 1600 and shot at 1/100s, and still had plenty of DoF.

The rule of thumb with an unstabilized lens is that you want your shutter speed to be at 1/focal_length or faster to eliminate camera shake blur while handholding. With an 85mm lens, that means 1/85s or faster, assuming you've got good handholding skills.

[NicolaB]

I am trying to remember everything and forgetting the basics now - I am going backwards before I go forwards (I hope).

I have not got used to the dof yet - only on the largest aperture. I was trying for the 'sweet spot' as everything was roughly the same depth but forgot to check out the shutter speed (I was in av).

I think my next step is to check out dof to see if there is a general guide to what you shoot at what depth - I know boke at wide open, sweet spot 8 & 11 for when depth not important (although I don't even know what it is for my lenses - must research) , smallest aperture to give widest range, but don't know when to use the others yet to their best advantage.

Good to know I can get nice mirror shots if I get my brain in gear!!!!!!!

Thank you.

[inkista]

Originally Posted by NicolaB

I am trying to remember everything and forgetting the basics now - I am going backwards before I go forwards (I hope).

You'll get there. Just go out and shoot a whole lot more!

I have not got used to the dof yet - only on the largest aperture. I was trying for the 'sweet spot' as everything was roughly the same depth but forgot to check out the shutter speed (I was in av).

Don't worry. After the motion blur thing happens enough times, you'll check the shutter speed. I had problems with it, too, when I first went telephoto.

I think my next step is to check out dof to see if there is a general guide to what you shoot at what depth - I know boke at wide open, sweet spot 8 & 11 for when depth not important (although I don't even know what it is for my lenses - must research) , smallest aperture to give widest range, but don't know when to use the others yet to their best advantage.

Sweet spot is f/5.6.

Wide open gives you the thinnest depth of field, but that also means focusing is at its most critical. And you may not have enough DoF to cover your entire subject. Wide open is also where your lens is probably at its weakest in terms of vignetting, purple fringing, (the 85/1.8 is notorious for this) and softness. So, only use it when you really need the shutter speed, more light, or the thin DoF. Otherwise, stopping down can always help you out.

And. Aperture is not the only factor when it comes to out of focus blur. You can get more or less blur depending on your distance from the subject (closer gives you more), your focal length (longer lenses have thinner DoF), and the distance of your subject from the background. These can all have as much or more affect on OOF blur as your aperture. The sensor size has an indirect effect on blur by making you a) use longer lenses, and b) get closer to subjects.

One last thing to remember: your camera holds the aperture at wide open while you're composing and focusing. The lens is only stopped down to the aperture setting you're going to use right before the picture is taken. This is done so that you (and the camera's metering and autofocus system) have the most possible light to see by. So, with the lens wide open like that, what you see through the viewfinder is NOT accurate to the DoF you're going to get in the image if your aperture setting isn't the max. aperture of the lens. That's why our dSLRs have DoF preview buttons on them.

[NicolaB]

Fabulous thank you! Lots to digest and commit to the expanding memory banks! :-)

I can't remember ever enjoying learning before!