Hyperfocal Distance and adapters

[Peter Rush]

Hi all - is anyone using the dofmaster.com for working out the hyperfocal distance of your lenses (not the stock lens) and how are you factoring in the adapter you are using - or can you simply use the calculator as it is and ignore the fact that you are using an adapter?

Pete

[Chris Harding]

Hi Pete

I am assuming that you are talking about the Metabones with focal reducer?? A dumb adapter uses the same settings.

If you feel really technical you COULD do a rough calculation based on the circle of confusion ... An APSC sensor has a COC of 0.02 and a Canon 5D III has a COC of 0.03 ... They use the COC to calculate DOF

I have read that the focal reducer changes the field of view by 0.7 so a 28mm lenses will give you 19.6mm right? Back calculate this and a 19.6mm lens will give you 29.4mm so they are reasonably close.

If it was me I would use a Full frame camera setting like a Nikon D800 or Canon 5D and that will be close but a tiny bit more DOF than you will actually get as the reducer doesn't actually take you all the all to full frame. As an example APSC (COC= 0.02) 50mm F2.8 at 10' away gives you 1.36' DOF ....FF (COC=0.03) gives you a bit more DOF and it goes to 2.06' .... So in short you need to select a camera (if it exists of course) with a COC of 0.25 (just to be safe and that will give you accurate DOF

If you don't want to calculate and be on the safe side I would just use the preset APSC FILM it has a COC of 0.025 which is halfway between apsc and FF and any error would be in your favour!!

Chris

[Bruce Macbryde]

I have read with interest your comment on DOF calculator.

Just a question, though. What camera setting do you use, APS film or 35MM Cinematography?

Also when setting the focal length do you use the measure of the lens or the 1.5 adjustment for APSC sensor?

[Chris Harding]

Hi Bruce

I'm using dumb adapters so I just use any preset that matches the sensor ..For the EA-50 the NEX5 will work and then again so will any of the APSC Nikon presets D7000 etcetc

As long as you have a circle of confusion of 0.02mm then it will be fairly accurate .. I still don't know if Pete figured out what the difference is with a Metabones ..On a dumb adapter you use the focal length that is marked on the lens not the 35mm equivalent ! The calculator takes the crop factor into account for you so if you are full wide at say 17mm then that's what you select not 17 x 1.5.

Chris