Why can't I see the shallow DOF through the viewfinder?

[JumboShrimp]

When I view an image through my wide-open 50/1.2L or my 100/2, I see a certain (shallow) DOF. But when I view the actual resulting digital image, the DOF has become much more shallow and the bokeh much more noticeable. Does the camera's viewfinder limit what you see in this regard, or is there some other optical magic at work here?

 

[privatebydesign]

Good eye and an accurate observation.

The focusing screen has an aperture of around f2.8, this only impacts the view to your eye through he viewfinder, not the AF module that is below the main mirror, or the sensor for the actual image.

You can fit 'faster' screens to some cameras.

 

[JumboShrimp]

Thanks, PbyD, but how does this hold up to the old saying that "Faster lenses are easier to (manually) focus?" Or are we talking about two different animals here?

 

[Bennymiata]

Thanks, PbyD, but how does this hold up to the old saying that "Faster lenses are easier to (manually) focus?" Or are we talking about two different animals here?

You're correct.
The faster your lens, the brighter the viewfinder.

 

[Eldar]

The lack of support for high precision focusing screens is something that irritates me with Canon. On the 1DX you can buy an Ec-S screen, but you need to control EC yourself. On the 5DIII and 5DS/DSR there are not even any Canon focusing screens to be bought. Considering you can have it fully supported on both the 6D and 7DII (+ lots of older bodies), it is almost a joke.

The use of such screens are naturally best suited for manual focusing and preferably on fast lenses, but as you state, it would be good to have it also for faster AF lenses, so you could see the actual DoF.

I have a custom made S-type focusing screen for my 5DIII (www.focusingscreen.com from Taiwan). It does not work as well as the Ec-S on my 1DX, but it is a lot better than the standard screen.

 

[rs]

Wide apertures such as f1.2 have much of the additional light over a slower lens coming in at quite oblique angles. The stock focus screen is matte, but not a very coarse matte. This makes it a happy compromise between being bright with slow lenses and able to show up depth of field with moderately fast lenses. A much more coarse surface is required to capture this off angle light from faster lenses. The downside is without the off angle light from a slow lens, the viewfinder will get much darker.

 

[e17paul]

Wide apertures such as f1.2 have much of the additional light over a slower lens coming in at quite oblique angles. The stock focus screen is matte, but not a very coarse matte. This makes it a happy compromise between being bright with slow lenses and able to show up depth of field with moderately fast lenses. A much more coarse surface is required to capture this off angle light from faster lenses. The downside is without the off angle light from a slow lens, the viewfinder will get much darker.

I have the eg-s on my 6D. Whilst there may be some loss of light, concerns about darkness are unfounded, even with my 70-300 zoomed to 300/5.6. For anyone with a compatible camera, the ultra matte screen is a worthwhile investment for manual focus.

 

[meywd]

The lack of support for high precision focusing screens is something that irritates me with Canon. On the 1DX you can buy an Ec-S screen, but you need to control EC yourself. On the 5DIII and 5DS/DSR there are not even any Canon focusing screens to be bought. Considering you can have it fully supported on both the 6D and 7DII (+ lots of older bodies), it is almost a joke.

The use of such screens are naturally best suited for manual focusing and preferably on fast lenses, but as you state, it would be good to have it also for faster AF lenses, so you could see the actual DoF.

I have a custom made S-type focusing screen for my 5DIII (www.focusingscreen.com from Taiwan). It does not work as well as the Ec-S on my 1DX, but it is a lot better than the standard screen.

Maybe the owner of focusingscreen.com is a Canon exec

 

[YuengLinger]

Wide apertures such as f1.2 have much of the additional light over a slower lens coming in at quite oblique angles. The stock focus screen is matte, but not a very coarse matte. This makes it a happy compromise between being bright with slow lenses and able to show up depth of field with moderately fast lenses. A much more coarse surface is required to capture this off angle light from faster lenses. The downside is without the off angle light from a slow lens, the viewfinder will get much darker.

I have the eg-s on my 6D. Whilst there may be some loss of light, concerns about darkness are unfounded, even with my 70-300 zoomed to 300/5.6. For anyone with a compatible camera, the ultra matte screen is a worthwhile investment for manual focus.

Not 'unfounded.' Significant darkening.

 

[Sporgon]

The lack of support for high precision focusing screens is something that irritates me with Canon.

To be fair the other dslr makers are worse. Nikon have forsaken interchangeable screens for some time now and although Pentax do them, if you want a true dof screen like the Canon 's' the advice on Pentax forums is to buy the Canon one and cut it down !

When Canon followed Nikon's example with the LCD overlay I suspect there were cost issues with making the screens work reliably; hence why the 7D and 5DIII didn't have them. I think they may have a cost effective solution because now the 7DII does have them. The reason the 5Ds doesn't is that it is pretty well a 5DIII architecture with a higher res sensor.

Expect the 5DIV to go back to having one, especially if, as I think, the IV may have an interchangeable prism, one OVF and the other an EVF which automatically locks the mirror up when fitted. This is if of course, the 5DIV is further video orientated.