Compensate for HFD?

[Wang Chung]

In order to not focus the lens in my street shooting, I select an aperture then pre-focus the lens to the hyperfocal distance to the DOF markings on the lens barrel.

Because the M8 sensor is cropped how badly is hyperfocal distance affected if I use the same settings I would use with the same lens on the M6? (My street lenses of choice are: Elmarit M 1:2.8/21mm Asph and Summilux M 1:1.4 35 Asph.

I really haven't noticed anything unusually out of focus but it seems to me that if the sensor is smaller I'd have to compensate when setting the HFD on the 8?

I'm somewhat confused here.

Thx...

Wang'r

[mcsol]

If anything, the DOF will be greater with the smaller sensor.

my 2 cents

[Paul Kay]

My own rule of thumb is to use the next widest aperture DoF markings - ie if you have the lens set to f/8 then use the f/5.6 scales. You will find loads of ideas/answers of theoretical grounds but this works pretty well for me (I've empirically tested it to my own satisfaction) - we tend to be rather more critical of digitally originated files!

[jaapv]

DoF relies on the lens, not the crop factor and thus no compensation is needed.


No it does not. The circle of confusion on a 1.3 crop sensor is 0.023 mm as opposed to 0.03 on 24x36.

The lens is only indirectly involved,DOF is determined by the total enlargement of the subject to the eye of the observer. I know it sounds counter-intuitive, but the fact that a wideangle lens produces a deeper DOF than a long lens is caused by the difference in enlargement between the two and is thus a result and not a cause.

The number crunching is bit too much to do on the fly, so This website (http://www.dofmaster.com/)
provides a handy tool

[jaapv]

My own rule of thumb is to use the next widest aperture DoF markings - ie if you have the lens set to f/8 then use the f/5.6 scales. You will find loads of ideas/answers of theoretical grounds but this works pretty well for me (I've empirically tested it to my own satisfaction) - we tend to be rather more critical of digitally originated files!

It is the most practical way to go about it.

[Wang Chung]

No it does not. The circle of confusion on a 1.3 crop sensor is 0.023 mm as opposed to 0.03 on 24x36.

The lens is only indirectly involved,DOF is determined by the total enlargement of the subject to the eye of the observer. I know it sounds counter-intuitive, but the fact that a wideangle lens produces a deeper DOF than a long lens is caused by the difference in enlargement between the two and is thus a result and not a cause.

The number crunching is bit too much to do on the fly, so This website (http://www.dofmaster.com/)
provides a handy tool
That is what I was sort of thinking. The crop factor affects the DoF and it makes sense if you look at the math of the COC. The crop factor makes COC smaller, and, as such would shorten (perhaps minimally) the depth of field. Then as Paul says using the next larger/wider aperture, i.e., f5.6 rather than f8 on the depth of field scale on the lens would give you a 'corrected for 1.33 lens factor' DoF.

I think I got it. Thanks JaapV for the site and Paul for the approach.

Wang'r

[Wang Chung]

My own rule of thumb is to use the next widest aperture DoF markings - ie if you have the lens set to f/8 then use the f/5.6 scales. You will find loads of ideas/answers of theoretical grounds but this works pretty well for me (I've empirically tested it to my own satisfaction) - we tend to be rather more critical of digitally originated files!
Thx Paul...will give that a go tomorrow.

Wang'r

[bmattock]

The lens does not know what the size of the sensor is. The marks are correct for that lens - on anything. I think. It gets confusing for me.

[jbf]

Look. Its the same way film works. The larger size of film, the less DOF. The smaller size film, the more DOF. Same thing with sensors.

[jaapv]

This thread (http://rangefinderforum.com/forums/showthread.php?t=26541&highlight=soup) will answer a number of questions..:)