The D750 AF Points are not the D810 AF Points

Started Sep 12, 2014 | Discussions
dojoklo Contributing Member • Posts: 526
The D750 AF Points are not the D810 AF Points
2

Based on the viewfinder and AF graphics provided in the Nikon D750 brochure, the location, size, and "spread" of the autofocus points of the D750 are not the same as the D810. The AF Points of the D750 are about 10% smaller, and don't reach as far to the left and right.

In this graphic, the darker points and inner brackets are the D750, and the lighter ones are the D810. The viewfinder grid is approximately the location of the DX Image Area.

Sometimes I feel like Nikon does this just so that I have to re-do all my graphics...

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fPrime
fPrime Senior Member • Posts: 2,858
Re: The D750 AF Points are not the D810 AF Points

dojoklo wrote:

Based on the viewfinder and AF graphics provided in the Nikon D750 brochure, the location, size, and "spread" of the autofocus points of the D750 are not the same as the D810. The AF Points of the D750 are about 10% smaller, and don't reach as far to the left and right.

In this graphic, the darker points and inner brackets are the D750, and the lighter ones are the D810. The viewfinder grid is approximately the location of the DX Image Area.

Sometimes I feel like Nikon does this just so that I have to re-do all my graphics...

Very interesting finding, dojoklo.  The two criticisms of Nikon's 51 point AF arrangement in the D810 and D700 was that there aren't enough cross type AF sensors and those that are there are don't sufficiently cover the field of view.  If the D750 is even more compacted then Nikon is heading in the wrong direction!

fPrime

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Joe Federer Senior Member • Posts: 2,502
Re: The D750 AF Points are not the D810 AF Points

I also wonder why they don't spread them out -- it's intensely frustrating, given I shoot with my subjects nearer the edge of the frame than the center-50% layout allows.

Carerra
Carerra Regular Member • Posts: 420
Re: The D750 AF Points are not the D810 AF Points
1

Joe Federer wrote:

I also wonder why they don't spread them out -- it's intensely frustrating, given I shoot with my subjects nearer the edge of the frame than the center-50% layout allows.

Completely agree with you, no doubt the D900 will be the camera to see new Cross type AF points from left to Right also,  Im hoping!

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fPrime
fPrime Senior Member • Posts: 2,858
Re: The D750 AF Points are not the D810 AF Points
1

Carerra wrote:

Joe Federer wrote:

I also wonder why they don't spread them out -- it's intensely frustrating, given I shoot with my subjects nearer the edge of the frame than the center-50% layout allows.

Completely agree with you, no doubt the D900 will be the camera to see new Cross type AF points from left to Right also, Im hoping!

This is a real reason to skip the D810 entirely and wait for the D900... only in the next Nikon generation are we likely to see an updated PDAF system.  What we have in the D810 and D750 now is simply the warmed over CAM 3500 FX from 2007, yikes!

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Jim Keye Senior Member • Posts: 2,197
Re: The D750 AF Points are not the D810 AF Points

Joe Federer wrote:

I also wonder why they don't spread them out -- it's intensely frustrating, given I shoot with my subjects nearer the edge of the frame than the center-50% layout allows.

Wider spread = more gaps. The only way to solve that is to make the individual sensors bigger so they cover more and leave less gaps. Then you need more processing power if you want to keep the performance up, particularly in tracking / multi-point modes. (And if you wanted the same battery life, you'd need a bigger battery to feed the processing.) So put all that together and you start wandering away from the price point nikon was apparently aiming at.

All this assumes there is actually a difference. Nikon has been known to do this. The specs say the same CAM module but the performance clearly varies. And let's face it, "II" doesn't necessarily mean it's a better version.

pcm81 Contributing Member • Posts: 835
Re: The D750 AF Points are not the D810 AF Points

Joe Federer wrote:

I also wonder why they don't spread them out -- it's intensely frustrating, given I shoot with my subjects nearer the edge of the frame than the center-50% layout allows.

To have a convincing argument for selling you a D900.

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chuxter Forum Pro • Posts: 21,714
Re: The D750 AF Points are not the D810 AF Points
2

dojoklo wrote:

Based on the viewfinder and AF graphics provided in the Nikon D750 brochure, the location, size, and "spread" of the autofocus points of the D750 are not the same as the D810. The AF Points of the D750 are about 10% smaller, and don't reach as far to the left and right.

Sometimes I feel like Nikon does this just so that I have to re-do all my graphics...

The graphics in that brochure were drawn by an artist, as was the one in the D810 brochure. I'm surprised you didn't know this.

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OP dojoklo Contributing Member • Posts: 526
Re: The D750 AF Points are not the D810 AF Points
2

chuxter wrote:

The graphics in that brochure were drawn by an artist, as was the one in the D810 brochure. I'm surprised you didn't know this.

Perhaps I should have said "based on the Viewfinder Display technical diagramin the brochure, which is typically the exact same diagram used in the manual, and which have been fully accurate in all past Nikon brochures!

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JasonED Contributing Member • Posts: 946
Re: The D750 AF Points are not the D810 AF Points

dojoklo wrote:

chuxter wrote:

The graphics in that brochure were drawn by an artist, as was the one in the D810 brochure. I'm surprised you didn't know this.

Perhaps I should have said "based on the Viewfinder Display technical diagramin the brochure, which is typically the exact same diagram used in the manual, and which have been fully accurate in all past Nikon brochures!

I doubt there is actually a difference.  It would make little sense for Nikon to produce a different AF module - unless the -3EV AF required a change.

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JSees Regular Member • Posts: 211
Re: The D750 AF Points are not the D810 AF Points

Jim Keye wrote:

Wider spread = more gaps. The only way to solve that is to make the individual sensors bigger so they cover more and leave less gaps.

Yeah, but bigger sensors mean that you may have trouble getting the AF to focus on something relatively small. It may choose something brighter or with more contrast that's also in the sensor area but not in the same plane.

They haven't yet made an AF that can read my mind!

Jim Keye Senior Member • Posts: 2,197
Re: The D750 AF Points are not the D810 AF Points

JSees wrote:

Jim Keye wrote:

Wider spread = more gaps. The only way to solve that is to make the individual sensors bigger so they cover more and leave less gaps.

Yeah, but bigger sensors mean that you may have trouble getting the AF to focus on something relatively small.

Indeed. It's one of the reasons closest subject priority was missed when nikon dropped it from the AF options. Obviously it doesn't solve the precision issue, but it sometimes did the trick.

It may choose something brighter or with more contrast that's also in the sensor area but not in the same plane.

It's one of the reasons people map out the AF sensors. Because they usually aren't exactly as marked, it can exacerbate the issue of "why didn't it focus there."

bobn2
bobn2 Forum Pro • Posts: 61,424
Re: The D750 AF Points are not the D810 AF Points
7

dojoklo wrote:

Based on the viewfinder and AF graphics provided in the Nikon D750 brochure, the location, size, and "spread" of the autofocus points of the D750 are not the same as the D810. The AF Points of the D750 are about 10% smaller, and don't reach as far to the left and right.

In this graphic, the darker points and inner brackets are the D750, and the lighter ones are the D810. The viewfinder grid is approximately the location of the DX Image Area.

Sometimes I feel like Nikon does this just so that I have to re-do all my graphics...

Maybe it's interesting to speculate why this new AF sensor wasn't used in the D4s and D810. Possibly it has to do with needing to fit in the smaller mirror box of the D600 chassis. Possibly one of the reasons for the D600's small AF area was that it used a straight DX AF module. Maybe the D750 is using the DX version of the multiCAM3500. I tested this theory by getting a picture of the D7100 VF, resizing it to DX compared with the FX of your picture above and overlaying it. This is the result.

Hmmm.

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Bob

bobn2
bobn2 Forum Pro • Posts: 61,424
Re: The D750 AF Points are not the D810 AF Points

JasonED wrote:

dojoklo wrote:

chuxter wrote:

The graphics in that brochure were drawn by an artist, as was the one in the D810 brochure. I'm surprised you didn't know this.

Perhaps I should have said "based on the Viewfinder Display technical diagramin the brochure, which is typically the exact same diagram used in the manual, and which have been fully accurate in all past Nikon brochures!

I doubt there is actually a difference. It would make little sense for Nikon to produce a different AF module - unless the -3EV AF required a change.

I think it's based on the DX module, see my post above.

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Bob

Jim Keye Senior Member • Posts: 2,197
Re: The D750 AF Points are not the D810 AF Points
4

bobn2 wrote:

Hmmm.

Well that pretty much removes any mystery as to what the D7200 will have in it...

sshoihet Senior Member • Posts: 2,629
Re: The D750 AF Points are not the D810 AF Points

Joe Federer wrote:

I also wonder why they don't spread them out -- it's intensely frustrating, given I shoot with my subjects nearer the edge of the frame than the center-50% layout allows.

The spread of the AF points is limited by the size of the sub mirror and also light falloff and distortion closer to the edges. I generally use the center 9 AF points because they're more sensitive and accurate.

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JasonED Contributing Member • Posts: 946
Re: The D750 AF Points are not the D810 AF Points

Thanks Bob.   Good comparison.

Of course now many will claim it is unusable because of this...

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fPrime
fPrime Senior Member • Posts: 2,858
Re: The D750 AF Points are not the D810 AF Points

bobn2 wrote:

dojoklo wrote:

Based on the viewfinder and AF graphics provided in the Nikon D750 brochure, the location, size, and "spread" of the autofocus points of the D750 are not the same as the D810. The AF Points of the D750 are about 10% smaller, and don't reach as far to the left and right.

In this graphic, the darker points and inner brackets are the D750, and the lighter ones are the D810. The viewfinder grid is approximately the location of the DX Image Area.

Sometimes I feel like Nikon does this just so that I have to re-do all my graphics...

Maybe it's interesting to speculate why this new AF sensor wasn't used in the D4s and D810. Possibly it has to do with needing to fit in the smaller mirror box of the D600 chassis. Possibly one of the reasons for the D600's small AF area was that it used a straight DX AF module. Maybe the D750 is using the DX version of the multiCAM3500. I tested this theory by getting a picture of the D7100 VF, resizing it to DX compared with the FX of your picture above and overlaying it. This is the result.

Hmmm.

Brilliant idea to compare the DX version of multiCAM3500 from the D7100, Bob.

We should all be cautioned that just because the D750 has the CAM3500 FX II does not mean that it's better than the D4s' CAM 3500 FX.  Version II in the D750 may indeed be worse.

The plot thickens...

fPrime

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JasonED Contributing Member • Posts: 946
Re: The D750 AF Points are not the D810 AF Points

fPrime wrote:

bobn2 wrote:

dojoklo wrote:

Based on the viewfinder and AF graphics provided in the Nikon D750 brochure, the location, size, and "spread" of the autofocus points of the D750 are not the same as the D810. The AF Points of the D750 are about 10% smaller, and don't reach as far to the left and right.

In this graphic, the darker points and inner brackets are the D750, and the lighter ones are the D810. The viewfinder grid is approximately the location of the DX Image Area.

Sometimes I feel like Nikon does this just so that I have to re-do all my graphics...

Maybe it's interesting to speculate why this new AF sensor wasn't used in the D4s and D810. Possibly it has to do with needing to fit in the smaller mirror box of the D600 chassis. Possibly one of the reasons for the D600's small AF area was that it used a straight DX AF module. Maybe the D750 is using the DX version of the multiCAM3500. I tested this theory by getting a picture of the D7100 VF, resizing it to DX compared with the FX of your picture above and overlaying it. This is the result.

Hmmm.

Brilliant idea to compare the DX version of multiCAM3500 from the D7100, Bob.

We should all be cautioned that just because the D750 has the CAM3500 FX II does not mean that it's better than the D4s' CAM 3500 FX. Version II in the D750 may indeed be worse.

The plot thickens...

fPrime

At least 1 online 'preview/review' has said the AF seems more confident and positive than the D800 (like the D810) so hopefully the 'back end' processing is the same as the D810.

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noirdesir Forum Pro • Posts: 13,586
Re: The D750 AF Points are not the D810 AF Points
2

Joe Federer wrote:

I also wonder why they don't spread them out

If it where technically possible to spread them out more Canon and Nikon would have done so for their $5000+ flagship sports DSLRs.

The two main reasons are the size of the AF sub-mirror (which is why the Sony SLT cameras can have a wider coverage, their 'AF mirror' can have the size of main mirror in (D)SLRs as it doesn't have to feed an optical viewfinder and doesn't have to fold away during exposure) and the general requirement of PD-AF to look at two opposing positions in the exit pupil which puts up restrictions at the image border even for the Sony SLT cameras. The only solution for edge to edge coverage is oversize the optical system (possibly even starting with the image circle) compared to the sensor size. Since the mirror or rather the AF-submirror is part of that optical system, oversizing the optical system includes oversizing the mirror and thus the flange distance.

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