FF & RF Best Aperture?

I'm just about to have a go at checking my K7 & K5 for FF & RF. Is there a best aperture? or is it best on a small aperture? say f16 where the DOF is big or better on a large aperture say f2.8 where possible to give a shallow DOF? OR should I stick with a middle aperture say f8?
CHEERS Vic.

Use wide-open if possible. With an AF lens the focus will
be wide open anyway. By using the same you record the
same.

-

Widest aperture possible is best to narrow the DOF.

Thanks to both of you. One more thing. Is it best to set it up on zoom lenses at the long end or the short end or the middle?
CHEERS Vic.

Vic the smallest aperture is what you need,the DOF is at its smallest

making it easer to adjust,if you do it at the largest(smaller number)

aperture this is where you need exact focus as you close the lens the

DOF is larger and doesn`t affect the shots as much.

Hope this is as clear as mud.

Jack.

I use the longest focal length for checking/adjusting zoom lenses. Having adjusted, I then check middle and short ends.

I'm just doing my K5-II now and it's at these times I wish a hadn't had so many LBA episodes in the past.

For now, I'm only doing the ones I use most often.

Thanks Peter. Bye the way what does LBA stand for? L=lens? B=buying? A=?

G'Day Jack. I think Jack that you have got it the wrong way round.
The smallest aperture (the biggest f number) gives the greatest DOF and The biggest aperture (the smallest f number) gives the shallowest DOF.
This I knew but did not know which to use. Fortunatly Algi and Peter Put me right. I can see the logic in their answer and that is what I'll use.
CHEERS Vic.

A = Addiction but can equally mean affliction

Yes, you do have it the wrong way round Jack.

To check focusing you use the largest aperture (aperture = size of the opening) which paradoxically equals the smallest f number.

The larger aperture produces a shallower depth of field (DOF) making the out of focus (OOF) parts of your target easier to determine whether you have FF or BF or none (if you are lucky).

By the way Vic, the terms are Front Focusing and Back Focusing, hence references to FF (when not related to sensor format) & BF, rather than RF as you have put in the title.

Sorry for that Vic it is the largest aperture smallest number.

Late night for me it is about 2am over here.

cheers, Jack.

Ps left out number,should read ,the smallest aperture number.

Peter. Iknew it was FF for front focusing I had a senior moment and put RF for rear focusing. I KNOW IT'S BF so slapped wrist for me
CHEERS Vic.

One thing to consider Vic is some lenses maybe soft wide open anyway. So, it may on occasion make sense to close down by half to a full stop

My Sigma 70-200mm EX DG OS lens seems quite soft wide open, but it's not really a problem as long as you can see that the most in-focus part of the image is as close to the focus point as you can get it.

When you close the aperture down the image might be sharper but it may also be less easy to see where the front and back of the DOF start to go out of focus to facilitate the adjustment.

Horses for course though, if necessary, use a number of settings and choose what you can work with.

I think you're kind of mixed up. DOF is at it's shortest when the lens is wide open, and that's where it should be to check for front focusing or back focusing.

edit. Should have read further before posting.