What is the Poor man's DOF Preview solution (Understanding Exposure text)

[NexC3buddy]

Hi guys,

Apologies if this is a covered question elsewhere - I couldn't find a thread for Byran Peterson's Understanding Exposure, so I'll ask the question and hope its make sense to any one who can teach a newbie.

On page 61 of the book, Peterson suggests how you can do a DOF preview if you don't have one of those fancy/pro cameras that have some special setting you can do that on. But when I dont' really understand what he means by "turn your lens one-quarter of a turn or so (as if you were removing the camera body, but don't actually remove it). When you do this you'll see the actual depth of field."

Okay, for the life of me, I can't move the lens unless I hit that eject button for the lens... in which case the lense would probably come off? How is that helpful to view DOF? Am I missing something?

I'm using a Sony Nex C3... so I also wonder does the EVF preview already do what he is trying to explain?

 

[Overread36]

With something like a Canon DSLR when one presses the remove lens button you release a lock, but the lens itself sits in a bayonet housing, so you have to turn the lens a few degrees before it will remove from the body. Try your own and see how the lens removes (I'd be very surprised if one press of the button just pops the lens of right there and then without any need to turn it).

 

[Destin]

Huh? That makes no sense. When you unhook a lens, it automatically stops down to it's smaller aperture (largest number) so I fail to see how that would help with a DOF preview.

 

[radiorickm]

I am not sure this will work with DIGITAL cameras and lens.

But in the OLD days, yes that was a trick you could use.

The aperature (on the lens) was connected to the camera by a little lever. When focusing, you always wanted the lens wide open, for the most available light on the focusing screen. As you pressed the shutter button, this lever pushed on the lens aperture bar (that came out from the back of the lens into the camera) casuing it to shut down to what ever aperature you had set on the lens.

When you turned the bayonet mount lens to release it from the camera, the aperture bar turned away from the lever, in effect stopping down the lens. (Which is what the DOF preview button does).

So, you could (not conveniently, I might add) look through the lens when fully attached to focus, and then rotate the lens to see a "stopped down" image as well.

Once again, this works on MANUAL cameras. I doubt it will work with electronically coppled lens, but I will have to check it out. I have a DOF preview, so I an't thought about this technique in years.

 

[Overread36]

radiorickm - That makes a lot of sense indeed and the Understanding Exposure book was originally written during the film era (or at least so early into digital that the majority were still on film). There are several editions of the book so an older one might well still be having this trick that won't work with most digital lenses (must admit I was scratching my head trying to work out how it worked); though if its a later edition it might simply be one of those slips where a bit of older data has held on by being overlooked in the revision.

 

[ann]

some cameras have a DOF preview button, this is not the same one as the lens locking device.

Check your manual to see if your camera has that function. On most cameras it will be found on the opposite side of the locking button near the base of the camera body.

Frankly, I find it a pain, as when stopping down it is hard to see anything let alone DOF

 

[KmH]

Apparently (profile) the OP has a Sony NEX C3.

 

[NexC3buddy]

Okay, that means what i see in the EVF previews the DoF because ... yes, I can see it makes a difference between the largest and smallest F/stops. Appreciate all the info folks!