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EOS 70D autofocus tracking???

Bazsl
Frequent Contributor

Will the phase detect 19 point AF system in the 70D track subjects moving toward the camera at 100 miles per hour in AI Server mode? In other words, is the 70D usable for still photos of aircraft in flight, horse racing and automobile racing? Any references to articles on the 70D AF sustem that discuss its ability to track subjects moving toward the camera would be appreciated. Thanks.

 

Bill

1 ACCEPTED SOLUTION

cicopo
Esteemed Contributor

If it's better than the 7D it won't be by much from what I've read but I haven't put any effort in that either. I have shot Radio Control events with a 7D with very good results & that's harder than full scale. I've also shot car racing with a 40D & had a pretty good keeper rate.

 

"A skill is developed through constant practice with a passion to improve, not bought."

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80 REPLIES 80

I would venture a bet. I bet a 5D Mk III, with your glass and in your hands would produce so nearly the exact same result that it would take a true pixel-peeper to see a difference.  If in fact if even there was any difference.

You however, like me I confess I still do it too, grab our 7D's and bolt up the big lens and go shoot.  Could also be why the birders snap up every 1D Mk IV there is and keep prices of used Mk IV's so high. There will be no more 1.3 crop bodies most likely and they want'em.  They want that extra reach, real or imaginary.

When I do a wedding, I sit the 7D at the back of the church on a tripod with the 100-400mm on it and probably always will.

 

Yor sig really tells it all ....

"A skill is developed through constant practice with a passion to improve, not bought."

EB
EOS 1DX and 1D Mk IV and several lenses!

cicopo
Esteemed Contributor

7D is long gone but served me well. It was pushed aside by one of those 1D4's and I do like it a lot. My current list of bodies is a Nikon D7100 (1.5 crop ratio) and the rest is all Canon 1d2n, 1Ds2 & the 1D4 plus a G9 (for underwater use) & SX50 IS to keep in the car. I bought the Nikon after giving a Nikon shooter some pointers at an event that got me thinking just how close the artificial reach might be between the D7100's 24 Mpixels at 300 mm and the 1D4's at 400 mm. The FOV for the Nikon was marginally wider but I had a lot more pixels on target with it which would allow deeper crops HOWEVER the Nikon lenses just can't af fast enough (or accurately enough) for my R/C stuff. I will also note they didn't cost anywhere near what my Canon lenses do. Good stuff for the money but doesn't meet my needs for R/C but it's a lighter travel kit. 

I'm sure I'd enjoy a 5D3 but what I have is doing the job perfectly & when I miss a shot or set it's me & not the equipment so buying a new body really won't net me any gains. Someone recently sold a 1Ds3 locally that really tempted me because they eventually lowered the price to $1800 before it sold & I was thinking any lower & I wouldn't be able to resist. There was also a 5D3 & 3 lens kit up for sale that tempted me but for now I'm happy with my results & the gear (bodies & lenses) I have so any extra money can be spent on travel or other hobbies.  

"A skill is developed through constant practice with a passion to improve, not bought."

garryjames
Occasional Contributor

Dear Cicopo,

 

Thanks for all your advice.  I try some of the exercises that you suggested in developing my panning techniques.  Your portfolio is very impressive!  You're a great photogrpher.  The R/C clubs are lucky to have you.  It seems that the  visibility of your work has really help raise a lot of funds.

 

So you seem to weigh in on Skirball's side, supporting the idea that a crop sensor will give better results than a FF cropped down.  Skirball's supposition is that more pixels in the image gives better image quality.  Author Tony Northrup supports this position.  Theoretical considerations seem to belie that claim based lens limitations.

 

Can you confirm that shooting say at 400mm on APS-C is better than shooting 400mm on FF and cropping?  Have you done controlled experiments?

 

On a new topic, I just read that Canon is planning to roll out a new 7D II sometime in summer or fall of 2014.  I heard that the 7D is much more robust and "pro-feeling" than the 70D.  What's your opinion of that?  Is the 7D II worth waiting for?

 

 

cicopo
Esteemed Contributor

I did a very quick comparison of the Nikon / 300 & Canon 1D4 / 400 last summer & it proved to be more pixels per duck for the Nikon. Unfortunately the Canon shot was OOF (camera focused behind the target) so although similar crops proved the Nikon had a bigger file the quality of the one image isn't really very helpful re sharpness etc. I'm planning on re doing the test because of this discussion & will try getting it done today (weather for today -Sat is rain but I think there should be some decent weather for a quick test. I intend to set up a test target & shoot with the camera locked down Plan is Nikon with both 70-300 VR & 28-300 VR at 300, Canon 1Ds2 with 100-400 @ 400, 1D4 with 100-400 @ 400.

I'm still thinking of a simple way to crop each sample to see the file sizes for an almost exact same FOV.

 

Re waiting for the 7D2 that's a tough call because of the things you may miss being able to shoot while waiting for actual stock to arrive on store shelves. Sometimes it's a short wait but not always and until we see real specs we have no idea just what's better about it & which fields of photography will benefit from it. Lets see how my test works out re the real or non existent artificial reach.   

"A skill is developed through constant practice with a passion to improve, not bought."

garryjames
Occasional Contributor

Dear Skirball,

 

Thank you so much for your response to ebiggs posting.  I would like to comment if I might...

 

Your second comment in response to ebiggs follws;

 

"ebiggs1 wrote:

 

When the FF image is 'cropped' to where it matches the “subject size” of the same image from the crop-sensor, there is not a great deal of difference in the image quality.  In this case of a 5D Mk II vs a 7D.

 


That's not necessarily true, not if the resolving power of the lens is good enough to not limit the crop sensor, and providing we're at low ISO.  You're now comparing an 8 MP image to an 18 MP.  It's a significant enough difference to be able to see."

 

If you review my posting of  05-12-2014 11:39 PM, you'll note that I address the issue of lens resolving power versus sensor resolving power.  

 

I can recommend a thorough article on resolving power in the following link:

 

http://vitaleartconservation.com/PDF/affects_of_lens_quality_on_image_resolution_v3a_draft.pdf

 

He states that lenses demonstrating 100 line pairs per mm (lp/mm) are, " Selected first-tier prime lenses at optimal f-stop; Nikon, Canon & Zeiss"

 

He states that lenses demonstrating 120 lp/mm are "  A handful of first-tier prime lenses at optimal f-stop (f/4.5-5.6); no LF or zoom lenses "

 

So allowing for 130 or 140 lp/mm is extremely generous in calculating lens resolving power.

 

This and many other authors quote that upper limit on the most excellent modern commercial lenses at 140 line pairs per millimeter and only under optimal conditions.

 

Based on that value, a FF sensor will have 14.5 effective megapixels.  An APS-C sensor will have 5.5 effective megapixels.

 

It should be clear from these considerations that the lens is the limiting factor in resolving power in APS-C sensors of greater than 5.5 megapixels and in FF sensors with greater than 14.5 megapixels.

 

If this is true, the APS-C offers no advantage over the FF cropped down.  ebiggs confirms this claim.  

 

Have you performed controlled experiments that refute this hypothesis?

 

garryjames
Occasional Contributor

Dear ebiggs1:

 

Thanks for your thought provoking discussion.  

 

I accept your experience that there is essentially no difference between an image from a APS-C sensor and an image from a FF sensor cropped down to APS-C size.  

 

The second part of my question:  Is the dual pixel focusing of the 70D superior to the Canon 6D focusing system.  

 

I'm having a lot of challenges getting the focus I want with the 6D.  I'm constantly switching between all 11 sensors and center spot sensor.  If I use all 11 sensor points while shooting birds, the camera usually chooses the closest point, which is usually not the bird, more specifically, not the bird's eye.  So I switch to center point and focus on the eye.  When the bird takes flight, I want to have all 11 sensors active as it's often too challenging to use the center point focus on the bird ( especially when the bird is far away and flying erratically.)  Also, the sensor has nothing other than the bird to focus on, so I'm pretty much sure that at least part of the bird will be in focus (assuming I track and half press the shutter release in time).

 

Seems like the 70D will be much better for birds in flight.  What do you think?  Is it worth buying the 70D to get the superior focusing technology?

 

An aside:  You quoted the pixel size of the 7D at 4.3microns.  I've read other references that confirm that quoted size.  I calculated the pixel size for square pixels and came up with 3.5 microns, smaller than the quoted value with no allocation for space between active pixel area.  The diagonal of a 3.5 micron square is 4.95 microns.  Still off of the quoted size of 4.3 microns.  If we allow 0.45 micron space between active pixel area, the pixel size comes out to be 4.3 microns.  Just so everyone knows, it appears that Canon is using the diagonal of the pixel to quote size.  

I can not comment specifically about hands-on use for a comparison between the 6D and the 70D. Since I own neither.

I have had a few folks in my class that have them but I personally do not have that expertise with either.

 

Remember it is possible with 'given' models, the crop factor advantage will be apparent and real. But when comparing similar models IE the EOS 7D and ESO 5D Mk II or Mk III, the crop advantage disappears.

 

I always use only the center, single point for birds or any wildlife for that matter  I use the center point almost 100% of the time.  And I have cameras that have 45 points!  All the newer Canon cameras are extremely capable at auto focus.

 

Your lens choice can also be a factor on focus speed and accuracy. The lens can also affect your crop image sharpness. Even considering my above statement about the crop factor advantage being little to none, if one camera has a superior lens compared to the other, all bets are off.  The better lens will most likely win out.  Glass is where it's at.

 

"Is it worth buying the 70D to get the superior focusing technology?"

I am sorry but did you mention a budget? And do you already own a camera?

 

... it appears that Canon is using the diagonal of the pixel to quote size.”

Again my fault,  Smiley Frustrated I should have made this clear. Sometimes my fingers get in front of my eye-teeth and I can't see what I am typing!  It is tough to put into words, that folks can understand, when it is second nature to old photographers like a few of us.

EB
EOS 1DX and 1D Mk IV and several lenses!

"You're a great photogrpher."

 

This is most likely the over ridding factor to whatever type photography issues you are discussing.  It helps to be good and have good technics.   And the more practice you have the better your shots will be.

EB
EOS 1DX and 1D Mk IV and several lenses!

garryjames
Occasional Contributor

Dear ebiggs1:

 

Do you use IS lenses?

 

Do they improve your keep rate?

 

GarryJames

Do you use IS lenses?

 

To me IS is a nice thing to have but it is not an end all. The closer you are to getting everything right, the better IS works.

My bag includes lenses from 8mm to 600mm. Both IS and non-IS.

Remember in the olden days we did not have IS and we got along just fine. We didn't even have auto-focus!

 

Do they improve your keep rate?

 

Every 'crutch' Canon comes out with improves my keeper rate. I am getting to the point after nearly 50 years of being in the business and the hobby anything they do is appreciated.

 

But always put your money in the best glass you can get. It really is in the lens.

 

EB
EOS 1DX and 1D Mk IV and several lenses!