Comments

Serena wrote on 12/16/2007, 2:34 PM
>>>At least the audio guys got their act together with dB<<<

One stop change halves or doubles (depending on direction of change) the amount of transmitted light. Since were talking about the area of the aperture (proportional to D squared) then the f/number changes by root 2 (1.414). I started in this lark at age 14 so the number sequence is burned in:
1.0, 1.4. 2.0, 2.8, 4, 5.6, 8, 11, 16, 22
The f/numbers marked on the lens don't become "stops" just because they're marked. My first cine camera had an f/3.5 lens (max aperture) just bit wider than f/4. But the lens was marked: 3.5, 4, 5.6, etc which didn't suggest that 3.5 to 4 was one stop. Same on the EX1 with max aperture of f/1.9.
Coursedesign wrote on 12/16/2007, 2:42 PM
How do you calculate the f/stop from a t/stop?

Easy.

You take the T-stop and subtract the light loss in each lens element, netting you the f/stop.

:O)

In practice there are three possibilities:

a) you have a cine lens with both T-stop and f/stop scales.
b) you have a cine lens with just a T-stop scale, so you look at the manual's conversion table for T-stop->f/stop.
c) you have a cine lens with no manual, but the manufacturer says it's T3-T22 with a maximum f/stop of f/2.8 (these numbers from Red's 18-50mm zoom), so if you're not working at full opening, you estimate to subtract 1/3 stop to get the f/stop.

farss wrote on 12/16/2007, 3:27 PM
Thanks,
I've edited my post, how did I get that wrong.

Bob.
Serena wrote on 12/17/2007, 12:48 AM
I have some frame grabs showing DOF in the sort of shots that could be similar to your interests. Give me an email address and I'll send them on. Not Moose at distance, but Parrots at about 4 metres and flowers at 1 metre.
PeterWright wrote on 12/17/2007, 12:55 AM
> "Not Moose at distance, but Parrots at about 4 metres and flowers at 1 metre."

Having trouble finding Moose in Melbourne, Serena?

Seriously - I'd like to see your frame grabs - can you post them somewhere?
Serena wrote on 12/17/2007, 3:22 AM
Moose are very scarce. Mice, OK. The frame grabs demonstrate only limited DOF and certainly are not great shots. Grabbed the camera when the Lorikeets turned up and pretty terrible lighting.
apit34356 wrote on 12/17/2007, 9:32 AM
I find it hard sometimes to read some of posts with the rural stories about "DOF" and lens design, but everyone has to start learning it somewhere and this forum is a good start. It would be very helpful for the above if Coursedesign,Farss,Serena and others could develop a nice little knowledge base for the sony users about basic optics. Then, lets talk to SPOT about putting together a nice book with this knowledge and "more advanced stuff" using the EX ----- should sell well --- I think!