Lots of Focus Points

[HDNitehawk]

I just thought of a new feature. Wouldn't it be cool if the focus points inside the viewfinder lit up "different colors" to let you know which type of focus point you were using, similar to the focus point graphics that we're looking at on the above link?

It might be interesting tothose of uswho pour of camera specs so they know exactly what their camera is doing. But then all this information seems to go out the window in my brain when some rare bird or animalpops up in front of my lens. Usually all my brain puts together in that situation is thatthe red flashy light just told me the bird is in focus.


I am sure you would see multiple posts on this site with the title "what do the different colorAF lights mean?".

[HDNitehawk]

But, how much 'blank space' between points exists on the 1D IV sensor? No idea...

You know this is frustrating. At some time in the past I found an article that actually shows this. It also had a detail of the actual area the af point covers in relation to each other. If I remember right it was put out by Canon.


I spent 30 minutes looking for it with no luck.

[neuroanatomist]

don't think that the MKIV had any dual cross points, but I believe that you mentioned that the 7D hadone dual-cross type point at the center.


It's amazing that a lot of the 7D technology has found it's way to the 1D X or that the1D X technology made it's way to the 7D for testing. Either way,I always thought that the 7D was pretty advanced.

Correct - no 1-series body before the 1D X has had a dual cross point, although the 7D has one...as do the 40D/50D/60D. Indeed, many of the 7D's features were brought to the series with the 1D X, or improved - you mentioned one earlier, Spot AF. It was interesting that Spot AF was available on the 1D IV, but only with a supertele lens attached, whereas on the 7D you can use Spot AF with any lens, which will be the case with the 1D X.

In addition to gainingtwo moref/2.8 cross type points, we are alsoupgrading 5 points to higher precision "dual-cross" type points, out of the total 41 cross type points.

True - but there's a trade off. Seems to be the story with the 1D X AF system. Yes, the 1D X brings 5 f/2.8 high-precision dual cross points to the 1-series...but it eliminates the ability to AF at f/8 with the center AF point, and while the center point of previous 1-series bodies operated in high-precision mode with an f/4 lens (like Rick's 500/4), the 1D X requires an f/2.8 lens for high-precision functionality with those 5 points.

Isn't it true that if we have 41 cross type points that are f/4 sensitive on the 1D X, thenthose same 41 points will alsobe cross type points that are also f/2.8 sensitive. So, sincethe MKIV had 39 cross type points and the 1D X has 41 cross type points, then it means that we are actually gaining 2 extra f/2.8 cross type points and that we are not losing any.

Technically, yes...but there's an additional implication that should be discussed, and it's yet another of those trade-offs that make it tough to say which is better. An f/2.8-sensitive sensor line has a wider baseline, meaning it can achieve a more accurate focus than a sensor with an f/4 baseline (but of course, the f/4 sensor works with more lenses).


With an f/2.8 lens, the 1D IV has 39 very accurate f/2.8-sensitive cross-type points, with the center one as high-precision. With the same f/2.8 lens on a 1D X, you have 5 even more accurate f/2.8 dual cross-type points, all of them high-precision, but 20 slightly less accurate f/4-sensitive cross-type points, and 16 slightly even less accurate f/5.6 cross type points. Also, on the 1D IV the f/2.8 points are spread across the frame, while on the 1D X the most accurate points are right in the middle. IMO, that means with an f/2.8 lens, the 1D IV is the winner - 39 spread out highly accurate cross-type points vs. 41 less spread out and mostly less accurate cross-type points.


With an f/4 lens, the 1D IV has just one cross-type point, although it operates at high precision. That same lens on a 1D X will have 20 equally accurate f/4-sensitive cross-type points at the sides, and 21 slightly less accurate f/5.6-sensitive cross-type points in the center block, for a total of 41 cross-type points vs. just one. So, the 1D X is the clear winner with an f/4 lens.


Here's where the exceptions on that list of Rick's from the 1D IV manual matter, since you have the 300/2.8 + 1.4x that is one of the exceptions. On the 1D IV, it will behave like an f/2.8 lens, as will the very commonly used 24-105mm and 17-40mm, and based on the criteria above, those lenses will be better on the 1D IV than on the 1D X. I honestly don't know if you'll get more accurate focus when using an exception-list f/4 lens on an f/2.8 sensor, compared to that lens on an f/4 sensor. I suspect not, but it will still be acting as a cross-type sensor - and the cross-type geometry is probably more important in overall performance than the aperture baseline, because in most situations, line orientation determines whether an AF point works at all, vs. subtle difference in accuracy.


So, based on the raw specs of the AF sensors, the lens(s) you have will impact which 1-series AF system is actually better for you (although that will be impacted by the benefit imparted by contributions from the metering sensor, no way to really quantify that). For example, I think you'd be better off with the 1D IV for your 300/2.8 + 1.4x, while Rick would be better off with the 1D X for his 500/4, unless he wanted to use it with the 2x TC, in which case he'd be better off with the 1D IV.


Head spinning yet? Mine is.....

[HDNitehawk]

So, based on the raw specs of the AF sensors, the lens(s) you have will impact which 1-series AF system is actually better for you (although that will be impacted by the benefit imparted by contributions from the metering sensor, no way to really quantify that). For example, I think you'd be better off with the 1D IV for your 300/2.8 + 1.4x, while Rick would be better off with the 1D X for his 500/4, unless he wanted to use it with the 2x TC, in which case he'd be better off with the 1D IV.


Head spinning yet? Mine is.....

I think the gains and losses will be only marginally noticed. But I havedecided that I am not going to pre-order the new 500mm or 600mm, or the 1D X. I am going to wait for the reviews.


Even thoughit only works with the supertele's, thespot focus on the 1D IV is superior to the 7D's IMO. The 1D IV puts the toggle function right at your fingertips on the big lenses, the 7D you had to go in and set the feature. I guess there is the possibility that I could have set a short cut for it, I didn't use the 7D long enough to figure out how.

[bob williams]

A common question is, "What does the relative spread of AF points look like?"

John, Wow, Great info. The way I understood the literature, the 1DX had a wider spread of AF points (I was hoping it would be enough to cover the "rule of thirds" intersections-----another dissapointment)-----By the way, the graphic (and explanation) is outstanding--I have never thought of saving a PS file as a PDF and have it retain the layers. I love this forum

[Richard Lane]

So, based on the raw specs of the AF sensors, the lens(s) you have will impact which 1-series AF system is actually better for you (although that will be impacted by the benefit imparted by contributions from the metering sensor, no way to really quantify that). For example, I think you'd be better off with the 1D IV for your 300/2.8 + 1.4x, while Rick would be better off with the 1D X for his 500/4, unless he wanted to use it with the 2x TC, in which case he'd be better off with the 1D IV.


Head spinning yet? Mine is.....

Sounds good to me, thanks!


Yes, you had my head spinning at "Reply."


-Rich

[Andy Stringer]

I'm curious as to why the macro lenses take such a big hit on AF point activation.

It's rare for me to enter a discussion on technical matters for fear of embarrassing myself, but I think I can help with this. At macro distances, the effective focal length of a macro lens increases, so the effective f number also increases. The following tables show the effective f number for different magnifications for two of Canon's macro lenses. I suspect that this has something to do with the limitation on AF point activation.

EF 180mm f/3.5L Macro USM

Magnification	1:10	1:5	1:3	1:2	1:1.5	1:1.2	1:1
Effective f/No.	3.8	4.0	4.3	4.7	5.0	5.4	5.8

EF 100mm f/2.8L Macro IS USM

Magnification	1:5	1:3	1:2	1:1.5	1:1
Effective f/No.	3.6	4.1	4.6	5.0	5.9