FF DoF

Digifrog

Digifrog

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Hi TP

Just to get a bit of understanding, is there any way of calculating a comparitive DoF between a APSC & an FF camera. That is to say I know that a FF sensor gives a shallower DoF than a cropped sensor. On my DX f/8 was the norm but shooting at f/8 on an FX will give a shallower DoF no?

How do I calculate the required DoF on an FX camera to equate to say f/8 on a DX camera?

Thank you.
 
Full frame will get you shallower depth of field at the same equivalent focal length. (Remember that the same 50mm lens on a full frame and a cropped will actually give different focal lengths so keep that in mind.)

So the things you need to know to use the table that geoff has given you is what aperture and focal length on the ff camera are you using. Once that is in the table look for the right aperture and distance. Once you have that number you can then put in the right focal length for the cropped camera you want and then simply look for the right aperture and distance.
 
AESamuel said:
Full frame will get you shallower depth of field at the same equivalent focal length. (Remember that the same 50mm lens on a full frame and a cropped will actually give different focal lengths so keep that in mind.)

So the things you need to know to use the table that geoff has given you is what aperture and focal length on the ff camera are you using. Once that is in the table look for the right aperture and distance. Once you have that number you can then put in the right focal length for the cropped camera you want and then simply look for the right aperture and distance.
Click to expand...

Thank you. Well I used to generally shoot at f/8 on my D80 and used the "third way into the frame", but I understand the same focal length and same aperture on a D800 will not give me the same depth.

I'm afraid I'm one of those people who have "number dyslexia", I see them but it's just a jumble for me.

f/8 DX = f/? FX at 24mm.
 
Digifrog said:
Thank you. Well I used to generally shoot at f/8 on my D80 and used the "third way into the frame", but I understand the same focal length and same aperture on a D800 will not give me the same depth.

I'm afraid I'm one of those people who have "number dyslexia", I see them but it's just a jumble for me.

f/8 DX = f/? FX at 24mm.
Click to expand...

Ok, on a full frame camera at 24mm focusing about 2 meters away (for example) you would get about 1 meter of focus at f8.

So get the same on an aps-c camera you would need to use a 16mm lens (to get a 24mm equivalent) and focusing about 2 meters away you would need to use f5.6 to get 1 meter of focus.

This was only hurriedly done as I am on my way out so I will have a better look later but I'm pretty sure I got that right.

Hope it helps,
Asa
 
Thanks Asa, yes my priority is to get acceptable sharpness as close as possible to infinity without encroaching too far into the realms of diffraction, so ideally f/8 - f/11 on the D800.

With an 18mm prime at f/8 on a D800 (if I've read the chart correctly) my HD is 5 feet so everything from 2.5 feet to infinity will be in focus.
 
Digifrog said:
That's helpful in one sense. I've nott seen that DoF chart before. It's comforting knowing that 18mm on a FF at f/8 focused on the HD everything from 2 feet to infinity will be sharp.

It doesn't tell me though what aperture on a FF is equivalent to f/8 on a crop sensor (?)
Click to expand...

Use this instead http://www.dofmaster.com/dofjs.html it is on the same site but allows you to choose the camera. :)
 
Digifrog said:
Hi TP

Just to get a bit of understanding, is there any way of calculating a comparitive DoF between a APSC & an FF camera. That is to say I know that a FF sensor gives a shallower DoF than a cropped sensor. On my DX f/8 was the norm but shooting at f/8 on an FX will give a shallower DoF no?

How do I calculate the required DoF on an FX camera to equate to say f/8 on a DX camera?
Thank you.
Click to expand...

F/number x crop factor ;)

And BTW, be wary of that 'focus one third-in' rule, it only works at medium kind of distances, like say groups of people or maybe street scenes. At very close range it's more like half way in, and in say landscapes when the far distance is at infinity, it's nowhere near 33:66 - could be 1:1,000,000.
 
Suvv said:
Use this instead http://www.dofmaster.com/dofjs.html it is on the same site but allows you to choose the camera. :)
Click to expand...

Thanks. Yes, I've seen that before.

HoppyUK said:
F/number x crop factor ;)
Click to expand...

I did actually think that, but I thought "naaa... cant be that simple".

For the type of photography I do, shooting at 18mm I just set the lens (manual focus only 18mm) to 4 feet at f/11 and as long as the closest object is more than 2 feet away everything should be sharp. I know it's going to take a few shots to trust my confidence with this.
 
Digifrog said:
Thanks. Yes, I've seen that before.



I did actually think that, but I thought "naaa... cant be that simple".

For the type of photography I do, shooting at 18mm I just set the lens (manual focus only 18mm) to 4 feet at f/11 and as long as the closest object is more than 2 feet away everything should be sharp. I know it's going to take a few shots to trust my confidence with this.
Click to expand...

That's almost right - HFD is 3.2ft ;)

But bear in mind that will only be 'sharp' according to the standard rules of acceptable DoF. If you're wanting to max out your D800E, then that is far too generous - by a long way.
 
HoppyUK said:
That's almost right - HFD is 3.2ft ;)

But bear in mind that will only be 'sharp' according to the standard rules of acceptable DoF. If you're wanting to max out your D800E, then that is far too generous - by a long way.
Click to expand...

So if the rock is 3 feet away I can focus on that and it will be sharp from there to ∞?

I shot this with my D80 and is a good example of my typical composition for this scene... the f/g rock, the b/g rocks and a well defined horizon. I think I focused on the f/g rock here.

6911161617_e0d626a66a_z.jpg


It may be generous but as a standard it could be my norm, but nothing wrong with altering the focus ring several times with the same frame.

So, how best to make that compromise between the acceptable DoF and maxing out the performance of the D800?
 
It's the accepted reference standard, but there are long arguments about DoF amongst landscapers and how best to manage it. For example, if you use HFD focusing as per your example, you are by definition putting both the closest subject and the far distance right at the limit of acceptable sharpness. And also what is acceptable to one person who only views on screen and another that likes to make A2 exhibition prints, is another question entirely.

Personally, I think the standard is a bit lax for critical landscape sharpness and if possible I tend to use one stop higher than suggested, eg set f/8 rather than f/5.6. Other people deliberately focus a bit fruther away to put a bit more sharpness into the far distance, assuming that those snow capped mountains in the distance are the main feature of the shot.

Those are sorts of arguments, but then you can't just keep raising the f/number because diffraction then begins to take its toll. That's when you end up with a T&S lens ;)

The point I was kinda making is that if you're happy with the DoF standard then it means you'll never realise the D800's resolution potential, at least not at the DoF margins.
 
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HoppyUK said:
It's the accepted reference standard, but there are long arguments about DoF amongst landscapers and how best to manage it. For example, if you use HFD focusing as per your example, you are by definition putting both the closest subject and the far distance right at the limit of acceptable sharpness. And also what is acceptable to one person who only views on screen and another that likes to make A2 exhibition prints, is another question entirely.

Personally, I think the standard is a bit lax for critical landscape sharpness and if possible I tend to use one stop higher than suggested, eg set f/8 rather than f/5.6. Other people deliberately focus a bit fruther away to put a bit more sharpness into the far distance, assuming that those snow capped mountains in the distance are the main feature of the shot.

Those are sorts of arguments, but then you can't just keep raising the f/number because diffraction then begins to take its toll. That's when you end up with a T&S lens ;)

The point I was kinda making is that if you're happy with the DoF standard then it means you'll never realise the D800's resolution potential, at least not at the DoF margins.
Click to expand...

Aye, maybe I should try my current system and HFD and see what happens. Maybe a spot of focus stacking is another option.

Don't worry Richard, one day I'll be ready for a Nikon T/S (P/C) :lol:
 
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