Jason Christie , Feb 13, 2012; 07:46 a.m.
Ok I'm sure it's been asked many times, but I've not bought many blads,..buying a 503cw with cfv 39 on back.....Lense is a 80cfe. Should
go with the 80... Or change for a 50 or 40? You're going to ask what I shoot? I'm a general all rounder loving ports and detailed L/scps.
After general chit chat, as I most enjoy candid, street, travel image making.
Leigh B. 
, Feb 13, 2012; 08:08 a.m.
I also have a CFV39, shooting it on a 555ELD body.
The sensor is almost as large as the film format, so the effective
focal length of the lenses doesn't change very much.
I would suggest using the 80, or possibly a 60.
The 50 and 40 are both definitely wide-angle lenses on the CFV-39.
- Leigh
Paul Loveteck , Feb 13, 2012; 11:48 a.m.
The CFV-39 is so precise that it is much less tolerant than film for focusing.
The 60mm will give you a little extra margin because of increased DOF.
Another thing to consider is weight and size for an all around lens. The 60 and 80 easily win against the 40 or 50 on this.
My recommendation would be a 60 CF. . .
Q.G. de Bakker 
, Feb 13, 2012; 12:13 p.m.
Shorter lenses do not have more DoF. And you would need more depth of focus, not depth of field.
Leigh B. , Feb 13, 2012; 01:39 p.m.
Shorter focal lengths definitely DO have greater Depth of Field.
That's why lenses on cell phone cameras are fixed focus,
because their FL is so short that they have very great DoF.
Depth of Focus is a function of the imaging system, whether
it be film or electronic. It can't be changed.
- Leigh
Q.G. de Bakker , Feb 13, 2012; 01:51 p.m.
Shorter focal lengths only produce less DoF if you use them to achieve lower magnifications, i.e. if you use them to produce completely different pictures.
Produce the same picture using a short and a long lens (and the same f-stop), and DoF will be the same in both.
Because you have to get much closer using the short lens, perspective will be hugely different. But DoF will not.
So a portrait shooter switching to a shorter lens in pursuit of the DoF he cannot get in the desired head shot using a longer lens, will find that all he accomplishes by doing so is to get too close to his sitter. Not a fraction of a mm more DoF.
If you want to use the word "definitely" in a more or less DoF context, the only true thing you can say is that you will get definitely more DoF when you reduce image scale, definitely less when you increase image scale. The concept of focal length does not figure in that at all.
Leigh B. , Feb 13, 2012; 02:30 p.m.
Q.G.,
Nobody but you said a word about "identical photos" or "different photos".
Paul and I are talking about the results when the camera is in a fixed position and you change lenses.
DoF increases as magnification decreases.
Magnification decreases with shorter FL.
Therefore... DoF increases with shorter FL.
q.e.d.
- Leigh
Q.G. de Bakker , Feb 13, 2012; 03:50 p.m.
Not at all, Leigh.
Paul suggested a shorter lens, because the less tolerant sensor demands more DoF.
Shorter lenses do not provide more DoF. (And you would not need more DoF, but more depth of focus.)
And nowhere a mention of "fixed positions", implied or explicit, until you brought it up.
Magnification does decrease when you put a shorter lens on, yes. But you cannot even pretend that apart from that, and DOF, everything else remains the same. So it's an entirely meaningless thing to say.
You have to say something about all of the rest (most important of which is the image you will capture) and how that changes too to begin making sense.
And the simplest way to truly understand DoF and it's independence of focal length is to get it firmly embedded in the matter between our ears that you cannot, and thus should not, hope to increase DoF in a given image by changing to shorter focal length lenses.
Or, if you insist, that provided you do not give the slightest for the resulting image, you can change DoF - and everything else (but who cares?) - by changing focal length.
Stuart Richardson , Feb 13, 2012; 04:03 p.m.
Maybe sell the 80CFE and pick up an 80mm CT* and a few hundred dollars towards a 50mm FLE? The 80mm lens has not changed optically since the beginning (or at least a very long time), so you are carrying around a lot of extra value in the CFE version that you may or may not need. It does have better ergonomics and a newer shutter assembly, but in terms of performance, they CT* is identical unless you are using a 200 series body.
Paul Loveteck , Feb 13, 2012; 06:57 p.m.
- The formula for DOF is:
- f is the focal length of the lens.
- This clearly shows that Leigh is correct and Q.G. seriously wrong unless he has is own mathematics. The formula also clearly shows that the DOF of a 60mm is greater than a 80mm.
- In addition, when Q.G. says " DoF in a given image..." this does not make any sense as an image does not have a DOF.
- DOF (Depth Of Field) is a precisely defined term and I recommend to Q.G. to go back to school before attacking serious members like Leigh.
