Af points comparison

Kellynikon

how can you compare the af point spread of different camera's?
i want to know how much difference there is in a D3100, D5100 and D750

Ironheart

this has been covered in a few threads, do a search. I'll do one too, and post results here

Ironheart

Here are a few:

http://forum.nikonrumors.com/discussion/3218/nikon-d750-general-discussion/p30
http://forum.nikonrumors.com/discussion/3218/nikon-d750-general-discussion/p18

Kellynikon

thanks, but im not talking about that. I want to make an overlay like this:
http://jtra.cz/stuff/essays/d610-vs-d800/viewfinder-af-coverage-comparison-d800-vs-d600.png

Ironheart

Find the jpegs of the focus points of all of the cameras you want to compare, and I'll plop them in photoshop if you can't.

Kellynikon

D3100: http://www.imaging-resource.com/PRODS/D3100/ZD3100VFCALLOUTS.GIF
D5100: http://www.imaging-resource.com/PRODS/D5100/ZVFCALLOUTS.GIF
http://nikonrumors.com/wp-content/uploads/2014/09/Nikon-D750-AF-screen.jpg

But arent the different sizes messing up the comparison?

spraynpray

That could be sorted in Photoshop as Ironheart doubtless intends to do. You ought to include the D7100 in there too as it has great AF coverage compared to those above.

That overlaid D610 and D810 shows that there is very little difference between the two which surprises me because a number of people here have criticised the D600/D610 to quite an extent on the basis that it's smaller field made it unusable for them whereas in that overlay, there is little difference. Interesting.

funtagraph

I dare to ask if those pictures of focus points are their design layouts or schematic pictures made for looking good in advertising or enough information? Only asking. Next question: Those are mixed FF and APS-C size cameras. A fair (?) comparison would switch D750 into DX and then the spread itself looks different. Best coverage of focus points in terms of "lots of points to choose all over the frame" has the 1-series.

spraynpray

But then if you switch the D7100 to 1.2 crop, the effective viewfinder is almost completely covered by focus points.

Kellynikon

Yes but im just curious on how the 'small' spread of the D750 compares to DX that I own

funtagraph

@spraynpray Yes, it's just that some RAW-converters having trouble with that mode. Or maybe were having problems when the cam came out.

PB_PM

Yes but im just curious on how the 'small' spread of the D750 compares to DX that I own

The size is the same, sort of. The entry level models (aka D3xxx or D5xxx) have a different system, which is smaller than the 51 point system to start with. The points on the smaller system tend to be spread out more, which is why features like 3D tracking and dynamic AF are less accurate.

Example the size: The 51point system in the D300/D300s/D7100 is the same as the D700 or D800. The difference? The total frame size. Nikon designed the FX AF system to cover the DX crop area, among other reasons. What are the other reasons? First, light fall off, which makes auto focus less effective on the outer points. This is already noticeable on any camera with the 39 or 51 point AF system, whether DX or FX. What I noticed in going from DX to FX is that the outermost points are more accurate, due to the larger frame, which leads to more light hitting them. Second reason, the angle of light hitting the focus points. The closer the AF points are to the edge of the frame the more distorted the light that reaches them are, which means focusing will be far less accurate. Thirdly, the larger the coverage area the larger AF sub-mirror must be, which will reduce viewfinder brightness.

Ironheart

The D5100 focus points are in red, overlayed onto the D750 frame. The D3100 and D5100 are identical.

Kellynikon

That is what I was looking for, thanks a lot youre not an ironheart but sweetheart

Ironheart

Awww, well it is Valentines Day :x I expect to see alot of roses on PAD @};-