cv15 and hyperfocal

[bloomy20]

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I just purchased this lens yesterday and haven't used it yet. As far as i gather from reading other posts, using hyperfocal is a good method in most cases for focusing.

 

Is the hyperfocal distance for such a lens at f8-1.2 metres? Also is it recommended to use the hyperfocal for f8 for example then stop down?

 

michael

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[scho]

See recommendations in this thread:

http://www.l-camera-forum.com/leica-forum/digital-forum/17258-focus-problems-cv15mm-m8-2.html

[lars_bergquist]

That thread does not seem to lead to much hard fact. But hyperfocal distance is easily computable. In the case of the 15mm and assuming a realistic circle of confusion (about half of that old 1/30th of a mm standard from the 1920's) you will have a depth of field from 1 meter to infinity if you set the lens to 2m and the aperture between 5.6 and 8, that is, to about 6.3.

 

The old man from the Age of Fix-Focus

[Chuck Hatcher]

The difference between theory and practice, in practice, is greater than the difference between theory and practice, in theory.

 

My empirical method:

 

1. Set desired aperture.

2. Set focus distance by guess.

3. Take a photograph.

4. Chimp!

5. See if distant objects are "acceptably" sharp (to me).

6. Repeat from step 2, increasing or decreasing as necessary to find limit.

7. Make a mental note of "trial and error hyperfocal distance" for lens/aperture.

8. Make a real note since mental notes aren't working like they used to.

 

Takes longer to describe than to do.

[vic vic]

mechael.. have no worries about focusing with this lens...

do a little exercise... take your rangefindered lens and play with guessing the disatnce... very soon you will see how eassy it is to eastimate... the error room for the 15mm must be huge even when it is on m8..

 

and........ then......

 

you want to do something good and valuable with your m8, besides talking techs?

 

take a look and contribute here with your cameras.

 

http://www.l-camera-forum.com/leica-...ys-photos.html

 

it is more important and more "leica spirit" and more photographic than talking techs

[lars_bergquist]

Chuck, chimping does not reliably indicate sharpness – not to the Leica standard, at least! And in this case the theory is well vindicated by practice.

 

Here is the general formula, where H = the hyperfocal distance, F = focal length, f = aperture and d = circle of confusion. The near limit of the zone of useable sharpness is H/2. I recommend a circle of confusion of 1/60th of a millimeter, that is, .015mm. –Do not mix sorts, use millimeters:

 

H = (F · F) / (f · d)

 

Easily done with a pocket calculator.

 

Chimps will have to use trial and error, I prefer thinking – because I find errors irritating.

 

The old man from the Depth of Confusion

[Chuck Hatcher]

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Chuck, chimping does not reliably indicate sharpness – not to the Leica standard, at least!

 

I don't know if my standard is higher or lower than the Leica standard, but if it's blurry on the LCD, I don't consider it sharp!

[jaapv]

It might be better to replace hyperfocal by scale-focussing.

[george_b]

you want to do something good and valuable with your m8, besides talking techs?

 

take a look and contribute here with your cameras.

 

http://www.l-camera-forum.com/leica-...ys-photos.html

 

it is more important and more "leica spirit" and more photographic than talking techs

Since this group is a broad church if you don't like a thread don't read or subscribe to it please. I'm not in the business of slagging off, just taking photos and contributing where a subject interests me.

[wparsonsgisnet]

.. is it recommended to use the hyperfocal for f8 for example then stop down? michael

 

If you are asking if the DOF will be even greater when you stop down, then the answer is yes.

 

But, for the M8, when you stop down further than f8, you should see your pictures begin to deteriorate from loss of resolution. This loss probably starts before you reach F8 but it is clear -- even for this chimp (that is, to the user when chimping) -- that the f11 picture is less desirable than the f8 picture.

 

Since most of the universe is in focus with the CV15 at f8, you may not need to stop down further than that anyway.

[mike prevette]

Scale focusing is a much better idea. With a little practice you will be amazed how accurate your eyes can be at judging distances.

[wparsonsgisnet]

The scale on this particular lens has the following distances marked:

 

1.25'

2.5'

4'

infinity.

 

It's a tough scale to use with any accuracy. Thank the gods for its DOF.

[lars_bergquist]

I don't know if my standard is higher or lower than the Leica standard, but if it's blurry on the LCD, I don't consider it sharp!

 

Correct—if it doesn't look sharp, it isn't sharp—but even if it looks sharp, it may not be really sharp. The proof is in the print.

 

The old King of the Chimps

[Vieri]

I just purchased this lens yesterday and haven't used it yet. As far as i gather from reading other posts, using hyperfocal is a good method in most cases for focusing.

 

Is the hyperfocal distance for such a lens at f8-1.2 metres? Also is it recommended to use the hyperfocal for f8 for example then stop down?

 

michael

 

Checking the DOF scale in the lens itself, you can see that at f4.5 everything between 1mt - infinity is in focus (more or less); as well, you can see that the focus marks are

 

0.3 - 0.4 - 0.5 - 0.7 - 1 - 2 - inf

 

from which you can infer that, except for very close subjects (wide open, DOF cover "only" 15-20 com at the closest focus distances), you are quite safe with not bothering to focus much if your subject is further than 1 mt. I use it almost all the time either wide open or at f5.6 - 6.3 (I never went after f8 so far) and focus guessing the distance and relying on the generous DOF. I haven't been disappointed yet...

 

Oh, and btw: I love the CV 15!

 

Hope this helps,

[george_b]

Just a query, is the depth of field as great on an M8 compared with say an M6 with film? I read somewhere that the depth of field is not as good, I tend to err on the side of caution when using the hyperfocal distances shown on the lens which may only be relevant to film cameras?

I have a nifty utility on my Palm Organiser - DOFMaster LE @ Hyperfocal Distance and Depth of Field Calculator - DOFMaster - if I'm trying to be 'clever'.

[lars_bergquist]

Just a query, is the depth of field as great on an M8 compared with say an M6 with film? I read somewhere that the depth of field is not as good, I tend to err on the side of caution when using the hyperfocal distances shown on the lens which may only be relevant to film cameras?

I have a nifty utility on my Palm Organiser - DOFMaster LE @ Hyperfocal Distance and Depth of Field Calculator - DOFMaster - if I'm trying to be 'clever'.

 

George, digital or film makes no difference in itself. What makes a difference is the film/sensor format. The smaller this is, the more must the image be magnified in order to reach a predetermined print size. And the greater the magnification, the smaller the circle of confusion has to be (given that the print is viewed from an unchanged distance).

 

Because of that, I work with a circle of confusion of 1/60 mm, not the old standard of 1/30. This is simple: just read the d.o.f. on the lens at half the aperture figure, e.g. if you use f:8, read at f:4 on the scale.

 

The old man from the Age of Scale Focusing

[wparsonsgisnet]

I believe the same lens on an M8 compared to a FF M6, say, has less DOF.

 

I understand this as the result of the lens "becoming longer" and that longer lenses have shallower depths-of-field, other things being equal (gotta love that phrase).

 

That said, when trying to estimate hyperfocal distance on the DOF scale, if including infinity in the setting, I place the infinity mark half the distance between the chosen aperture and the next wider one (that is closer to the focus mark).

 

But I do the same thing with film M's (FF camera), so I'm *not* doing anything special for the 1.33 factor.

 

Here is an image taken this week with infinity set inside the indicated f-stop location on the DOF scale.

 

CV15, B-W 486 IR-cut filter, iso 640, 1/90, f5.6 or f8, Edmund linear profile, some exposure corrections using curve in C1-LE, no other stuff done to it except to downsize it for the Forum.