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Author Topic: A7RII Vs 5ds R  (Read 14622 times)

eronald

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Re: A7RII Vs 5ds R
« Reply #40 on: October 30, 2015, 03:43:01 am »

Thank You Edumund, but . . .

Your not familiar on how we prepare, or what we shoot. 

We tried both, the 7s and R  . . .  zero difference, though if you shoot trees and buildings with time in, plan it, set, it light it view it on a big screen both these two little Sony's work.

But in severely heavy conditions, working out of a military Blackhawk, bouncing backwards on a 75mph atv, hanging ten feet out of a 1200 hp skiff then no they don't.

For video pretty good, for stills not.

It takes a Nikon or Canon.  Period, cause we tried the sony way.

Sony makes nice stuff, Canon and Nikon . . .  Military grade.

Even fast moving environmental portraits, you need to see it focus to be dead on.

Everyone talks pixels and the other stuff but traditional Rules when the SITF and there is blood on the floor.

IMO

BC

Well, nice to hear that  the embedded press won't be using Sony still cameras :)
I guess only the salad-grazing landscape shooters will be able to track their prey and convert to Sony ...

Edmund
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ErikKaffehr

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Re: A7RII Vs 5ds R
« Reply #41 on: October 30, 2015, 03:51:49 am »

Hi,

You need 90PPI at 1m viewing distance. For a 60" inch wide print you thus need 90x60 = 5400 pixels. If you divide 36 mm with 5400 you end up with 6.7 microns of, which would be your CoC for that distance.

Putting this into the hyperfocal distance formula H = f^/Nc you get 50 * 50 / ( 8 * 0.0067) = 46642 mm, that is 46 m, so the hyperfocal distance for your print size with 20/20 vision would be 46 m on 50 mm lens at f/8. I have not seen any 50 mm lens ever with a marking at 46m (or 50m) on the focusing scale. The one I happen to have close by has markings for infinity and 5m. 

The 6.7 microns would correspond to around 20 MP on a full frame DSLR. So that is all you need for 60" wide print, when viewed at 1m.

Actually, it is much smarter to look at the sensor side of the thing. If you need a CoC of 6.7 microns and use aperture f/8 the amount of acceptable defocus would be 0.0067 * 8 = 0.054 mm. That figure will be the same for any lens at f/8, regardless if it is an ultratelephoto or an ultrawide.

So, what does this give us?

  • You need about 20 MP for that print, viewed at that distance
  • Focusing at around 50m on a 50mm lens at f/8 will give you an image that is sharp at that print size and viewing distance from 25m to infinity.
  • To achieve the same above you need a focusing accuracy of about 0.05 mm in the focusing plane, at f/8. That figure does not depend on the focal length.

Best regards
Erik


I agree, to a point. But if you do the same calculations based on a 60" wide print that appears sharp when viewed from 3.3 feet (1m) by a person with normal eyesight, you end up with everything from 143 feet to infinity appearing sharp when the lens is focused at 300 feet and set to f/1.4. At f/8 it's 41 feet to infinity. If the person has 20/20 vision it's different. That requires an aperture of f/4 for everything to from 147 feet to infinity to appear sharp when focused at 300 feet. At f/8 you get 97 feet to infinity "sharp". Still, it's a 60" print viewed from a couple feet away, and we haven't even tossed in deconvolution sharpening, which changes everything. For any reasonable intent I think DOF is quite useful, but you can't use numbers for 8x10 prints if you're doing 30"x40" prints.
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eronald

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Re: A7RII Vs 5ds R
« Reply #42 on: October 30, 2015, 04:52:49 am »

Hi,

You need 90PPI at 1m viewing distance. For a 60" inch wide print you thus need 90x60 = 5400 pixels. If you divide 36 mm with 5400 you end up with 6.7 microns of, which would be your CoC for that distance.

Putting this into the hyperfocal distance formula H = f^/Nc you get 50 * 50 / ( 8 * 0.0067) = 46642 mm, that is 46 m, so the hyperfocal distance for your print size with 20/20 vision would be 46 m on 50 mm lens at f/8. I have not seen any 50 mm lens ever with a marking at 46m (or 50m) on the focusing scale. The one I happen to have close by has markings for infinity and 5m. 

The 6.7 microns would correspond to around 20 MP on a full frame DSLR. So that is all you need for 60" wide print, when viewed at 1m.

Actually, it is much smarter to look at the sensor side of the thing. If you need a CoC of 6.7 microns and use aperture f/8 the amount of acceptable defocus would be 0.0067 * 8 = 0.054 mm. That figure will be the same for any lens at f/8, regardless if it is an ultratelephoto or an ultrawide.

So, what does this give us?

  • You need about 20 MP for that print, viewed at that distance
  • Focusing at around 50m on a 50mm lens at f/8 will give you an image that is sharp at that print size and viewing distance from 25m to infinity.
  • To achieve the same above you need a focusing accuracy of about 0.05 mm in the focusing plane, at f/8. That figure does not depend on the focal length.

Best regards
Erik

What is typical FF mounting yaw tolerance?
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Rob C

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Re: A7RII Vs 5ds R
« Reply #43 on: October 30, 2015, 05:13:17 am »

If that is the case, that PDAF and CDAF would suffer equally from this in focus accuracy.

Hi Chuck,

Perhaps they do, perhaps not - I only know about the one lens on the body where I tried to make that infinity shot. My other af lens is a very seldom-used 2.8/180mm Nikkor that has never been used for distance shots - just for closer subjects where I wanted to make tighter images, sometimes deliberately OOF to some extent or the other.

I'm not a landscape shooter and so infinity's a bit far away for me. At least, photographically speaking.

;-)

Rob C

AreBee

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Re: A7RII Vs 5ds R
« Reply #44 on: October 30, 2015, 05:41:56 am »

Rob,

Quote
I'm not a landscape shooter...

Thanks.
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ErikKaffehr

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Re: A7RII Vs 5ds R
« Reply #45 on: October 30, 2015, 05:42:38 am »

Hi,

I don't know, would like to know. The only figures I have seen specified was:

30 Microns for the Hasselblad V series
12 Microns Phase One backs
+/- 20 microns for Leica (possibly +/- 10 microns for digital Leica)

That figure is of course not for yaw. Some yaw may also come from flexing of the springs in the mount.

I would expect that later generation cameras would have less variation.

I don't think that yaw is a major issue, at least if lenses like the Otus 85/1.4 can achieve uniform sharpness over the field at f/1.4 when mounted on camera and that often seems be the case.

Something I have seen specified that Canon AF-systems are accurate to 1/3 DoF on professional systems. Roger Ciala looked at this and essentially found that modern Canons (5DIII) combined with same generation lenses focus pretty accurately and with good repeatability. Still according to Roger Ciala, Nikon not as good.

This article by Roger is somewhat geek oriented, but offers good insights: http://www.lensrentals.com/blog/2012/08/autofocus-reality-part-3b-canon-cameras

What that article shows is that Canon has significantly improved the AF accuracy on the 5DIII, but it needs late generations lenses.

Best regards
Erik

What is typical FF mounting yaw tolerance?
« Last Edit: October 30, 2015, 06:06:13 am by ErikKaffehr »
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Chris Livsey

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Re: A7RII Vs 5ds R
« Reply #46 on: October 30, 2015, 06:15:33 am »

I have not seen any 50 mm lens ever with a marking at 46m (or 50m) on the focusing scale. The one I happen to have close by has markings for infinity and 5m. 
Best regards
Erik

Pedantically  ;)
My 50mm Voigtlander S Nokton ASPH f1.5  Nikon RANGEFINDER lens is marked at 5, 7, 10, and 20m but I grant you not at 50m but then the camera focussing system dates to the 1950s and we have progressed haven't we?
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ErikKaffehr

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Re: A7RII Vs 5ds R
« Reply #47 on: October 30, 2015, 01:29:18 pm »

That was a nice focusing ring…

Erik

Pedantically  ;)
My 50mm Voigtlander S Nokton ASPH f1.5  Nikon RANGEFINDER lens is marked at 5, 7, 10, and 20m but I grant you not at 50m but then the camera focussing system dates to the 1950s and we have progressed haven't we?
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eronald

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Re: A7RII Vs 5ds R
« Reply #48 on: October 30, 2015, 02:58:09 pm »

You may need to correct me but "reverse telephoto" designs can accept much more yaw than designs with an exit pupil close to the film plane.
The distance of the exit pupil to film on eg. an 8mm SLR lens is ... a bit larger than 8mm :)
And so presumably the depth of focus (and hence the amount of acceptable yaw) is much greater on SLRs.
So in a way, SLRs can be made to lower tolerances than rangefinders ...
All of this is just a conjecture based on elementary geometry ...

Edmund

Hi,

I don't know, would like to know. The only figures I have seen specified was:

30 Microns for the Hasselblad V series
12 Microns Phase One backs
+/- 20 microns for Leica (possibly +/- 10 microns for digital Leica)

That figure is of course not for yaw. Some yaw may also come from flexing of the springs in the mount.

I would expect that later generation cameras would have less variation.

I don't think that yaw is a major issue, at least if lenses like the Otus 85/1.4 can achieve uniform sharpness over the field at f/1.4 when mounted on camera and that often seems be the case.

Something I have seen specified that Canon AF-systems are accurate to 1/3 DoF on professional systems. Roger Ciala looked at this and essentially found that modern Canons (5DIII) combined with same generation lenses focus pretty accurately and with good repeatability. Still according to Roger Ciala, Nikon not as good.

This article by Roger is somewhat geek oriented, but offers good insights: http://www.lensrentals.com/blog/2012/08/autofocus-reality-part-3b-canon-cameras

What that article shows is that Canon has significantly improved the AF accuracy on the 5DIII, but it needs late generations lenses.

Best regards
Erik
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Rob C

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Re: A7RII Vs 5ds R
« Reply #49 on: October 31, 2015, 05:14:55 am »

Rob,

Thanks.


Ooops! Hadn't imagined you were really expecting a reply; a quick look at my website would have shown you my interests.

Actually, not strictly unconcerned with landscape, as I do find some things interesting but not in any sort of traditional sense of the definition of landscape, if there is one.

Here's the kind of thing I find intriguing, especially as I pass it at last three times a week. You should see the place in the rain...

Rob C




eronald

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Re: A7RII Vs 5ds R
« Reply #50 on: October 31, 2015, 08:20:15 pm »


Ooops! Hadn't imagined you were really expecting a reply; a quick look at my website would have shown you my interests.

Actually, not strictly unconcerned with landscape, as I do find some things interesting but not in any sort of traditional sense of the definition of landscape, if there is one.

Here's the kind of thing I find intriguing, especially as I pass it at last three times a week. You should see the place in the rain...

Rob C


HALLOWEEEEEEEEEEEEEEEEENNNN !!!!!!!!!!!!!!!!!

Edmund
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Rob C

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Re: A7RII Vs 5ds R
« Reply #51 on: November 01, 2015, 04:05:12 pm »

HALLOWEEEEEEEEEEEEEEEEENNNN !!!!!!!!!!!!!!!!!

Edmund


Well, Edmund, it's not easy staying topěcal; I deserve a medal!

;-)

Rob C

eronald

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Re: A7RII Vs 5ds R
« Reply #52 on: November 02, 2015, 04:54:16 pm »

Make your own!

https://www.youtube.com/watch?v=gNjjEhD-Aig

E.


Well, Edmund, it's not easy staying topěcal; I deserve a medal!

;-)

Rob C
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Rob C

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Re: A7RII Vs 5ds R
« Reply #53 on: November 02, 2015, 05:06:50 pm »

Make your own!

https://www.youtube.com/watch?v=gNjjEhD-Aig

E.


Ah... my fingers aren't as pretty. But hey, I appreciate the suggestion, which reminds me of the Rolling Stones.

;-)

Rob

Oh, I don't know: maybe the fingers ain't so bad after all:
« Last Edit: November 02, 2015, 05:28:47 pm by Rob C »
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