Sorry, missed that in the deluge of emails on this topic. Was just trying to help.
On May 30, 2012, at 1:53 AM, Howard Jones wrote: > As mentioned a couple of times, this one was sent by mistake and the one > involving crop factors being the more accurate scenario. By all means keep > picking faults in this email if you wish. > > From: Joe Laude <[email protected]>; > To: Nuke user discussion <[email protected]>; > Subject: Re: [Nuke-users] Arri Alexa sensor size - camera tracking question > Sent: Wed, May 30, 2012 6:05:08 AM > > I have no idea how you could have come across two 500mm lenses, except one > isn't really a 500mm. If you have a moment, send a link to the product's page > on Adorama or B&H or Amazon or wherever you like, so I can see what you're > looking at, because I have never seen a "full-frame-equivalent focal length" > used in place of the actual focal length of a lens. Canon doesn't, and I > suspect Nikon doesn't either. > > On May 29, 2012, at 1:04 PM, Howard Jones wrote: > >> Ok then explain to me why I have a 500 mm lens that fits my Nikon that will >> give the same as a 750mm lens designed for the camera. The sensor has >> cropped the image coming through the back of the lens and effectively >> changed the focal length. >> >> I can buy a 500mm lens designed for my camera and that will give me the >> field of view of a 500mm. >> >> So I now can have 2 500 mm lenses on the same camera but with completely >> different results depending on which one I use. >> >> I assume I'm missing something here, but as there are 2 lens types available >> for my camera, one designed for it and one that happens to use the same >> mount both 500mm isn't there 2 possible results from a '500mm ' lens? >> >> It's this scenario I'm talking about, and I believe the one that has sparked >> the thread in the first place. >> >> H >> >> From: Joe Laude <[email protected]>; >> To: Nuke user discussion <[email protected]>; >> Subject: Re: [Nuke-users] Arri Alexa sensor size - camera tracking question >> Sent: Tue, May 29, 2012 9:50:20 AM >> >> Alex is correct. The cone of light coming through the lens doesn't change >> because of the sensor. The sensor determines how much of that light is >> recorded as an image, but an 18 is an 18 on any sensor. A bigger sensor will >> give you a wider fov when you're shooting, but that's irrelevant to the >> figures you put into Nuke after it's been shot. The lens is still an 18mm >> lens, and you don't need to convert it to something else. >> >> Joe Laude >> (507) 251-7006 >> Sent from my iPhone >> >> On May 29, 2012, at 1:49 AM, Alex Fry <[email protected]> wrote: >> >>> It doesn't matter what sensor the lens is designed for, it's focal length >>> remains the same. It is what it is. >>> >>> What are you basing 27mm on? A crop factor of 1.5? Relative to what? A 35mm >>> still camera? >>> >>> 35mm stills equivalent focal length descriptions should have no place in a >>> discussion about tracking footage from a movie camera, they only exist as a >>> crutch for stills photographers who grew up using their focal lengths as >>> working slang to describe a particular field of view. >>> >>> >>> >>> On 29/05/2012, at 6:23 PM, Howard Jones <[email protected]> wrote: >>> >>>> I'd agree with Randy here. If the 18mm prime is not designed for the film >>>> back then it would have an equivalent focal length of, in your example of >>>> 27mm (though that is just based on your example. ) >>>> >>>> However if it is a prime lens designed for the chip, then it is an 18mm >>>> lens, so no conversion necessary. >>>> >>>> However again, the solve you would get should work either way, but the >>>> relation between the point cloud and camera will vary and will begin to be >>>> an issue for objects that should be close to the camera. >>>> >>>> That is you can double a focal length and move an object twice as far away >>>> in nuke and it should look the same, except for objects very close, when >>>> distortion artefacts creep in, and I don't mean lens distortion >>>> characteristics here before any one jumps in, I mean if you stick a sphere >>>> right next to the lens and have a super wide angle, that isn't the same as >>>> an object further away with say a standard lens size. (eg 50mm for 35) >>>> >>>> So you can track and try 2 solves with 2 different lens lengths, and if >>>> there are objects close to camera you should see a difference in shape of >>>> any test spheres etc, otherwise it should still lock. >>>> >>>> I couldn't find anything quickly online to confirm your film back sizes, >>>> but someone has created a whole set of presets for cameras (Nathan?) which >>>> are very useful on nukepedia. >>>> >>>> H >>>> >>>> From: [email protected] <[email protected]>; >>>> To: Nuke user discussion <[email protected]>; >>>> Subject: Re: [Nuke-users] Arri Alexa sensor size - camera tracking >>>> question >>>> Sent: Tue, May 29, 2012 7:21:12 AM >>>> >>>> He is right. >>>> >>>> T-Mobile. America’s First Nationwide 4G Network >>>> >>>> ----- Reply message ----- >>>> From: "Darren Coombes" <[email protected]> >>>> To: "Nuke user discussion" <[email protected]> >>>> Subject: [Nuke-users] Arri Alexa sensor size - camera tracking question >>>> Date: Tue, May 29, 2012 01:01 >>>> >>>> >>>> Thanks for the reply Alex, I'll have a look. We have someone here saying >>>> that the 18mm lens would not be an 18mm lens in our tracker settings, I >>>> just want to make sure what they are saying is right. >>>> >>>> Cheers. >>>> D. >>>> >>>> On 29/05/2012, at 4:57 PM, Alex Fry wrote: >>>> >>>>> The "crop factor" is described by the sensor measurements you input. >>>>> Your 18mm lens is still 18mm, no conversion is necessary, your field of >>>>> view has changed, but not your focal length.. >>>>> An 18mm lens has a different field of view if its mounted on micro4/3, >>>>> DX, super35, 35 stills, 70mm or medium format, but it remains an 18mm >>>>> lens. >>>>> >>>>> Have a play with Nuke's camera node, tweaking the focal length, haperture >>>>> & vaperture knobs to get a feel for the relationship they have to each >>>>> other. >>>>> >>>>> -Alex >>>>> >>>>> On 29/05/2012, at 4:27 PM, Darren Coombes >>>>> <[email protected]> wrote: >>>>> >>>>>> Hi, we have some plates shot with the alexa on a 18mm prime lens. >>>>>> I Need to camera track this material. >>>>>> >>>>>> On the Arri website, it says the sensor size for the alexa is 23.76 x >>>>>> 13.37mm when using the ARRIRAW setting with 1.78:1 aspect ratio. >>>>>> >>>>>> in the camera tracker settings, would I put the film back size as 23.76 >>>>>> x 13.37mm? >>>>>> And then I guess i need to find out the crop factor for that sensor size >>>>>> and use that when entering the focal length of the lens? >>>>>> >>>>>> So if we shot on a 18mm lens, and theoretically the crop factor was 1.5 >>>>>> (not sure what the actual crop factor is yet), you would times 18 x1.5? >>>>>> and that would give the right focal length? >>>>>> >>>>>> Can someone point me in the right direction with this? and is my theory >>>>>> of this right? or am i missing something? >>>>>> >>>>>> Thanks. >>>>>> >>>>>> Darren. >>>>>> >>>>>> >>>>>> >>>>>> Darren Coombes >>>>>> >>>>>> Compositor >>>>>> >>>>>> www.resolutiondesign.com.au >>>>>> >>>>>> >>>>>> resolution: sydney australia tel: +61 2 9360 9908 fax: >>>>>> +61 2 9360 8908 >>>>>> 22 burton st: east sydney: 2010 post office box: 614 darlinghurst: 1300 >>>>>> abn: 3305 196 1856 >>>>>> >>>>>> 2010 Silver One Show Entertainment Award: Online Branded Entertainment >>>>>> 2009 Gold Promax/BDA Award: Best Broadcast Design Image Spot >>>>>> 2009 Winner Creative Review Hotshop Award: Post Production / VFX >>>>>> 2009 Finalist Creative Review Hotshop Award: Broadcast Design >>>>>> >>>>>> >>>>>> The information transmitted, together with the attachments, is intended >>>>>> only for the person or entity to which it is addressed and may contain >>>>>> confidential and/or priviliged material which may be subject to >>>>>> copyright. Any review, retransmission or other use of, or taking of any >>>>>> action in reliance upon, this information by persons or entities other >>>>>> than the intended recipient is prohibited. If you received this in >>>>>> error, please contact the sender and delete the material from any >>>>>> computer or network. No warranty is given by the sender that any >>>>>> attachments to this email are free from viruses or other defects. >>>>>> >>>>>> >>>>>> <Unknown.jpeg> >>>>>> >>>>>> _______________________________________________ >>>>>> Nuke-users mailing list >>>>>> [email protected], http://forums.thefoundry.co.uk/ >>>>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >>>>> _______________________________________________ >>>>> Nuke-users mailing list >>>>> [email protected], http://forums.thefoundry.co.uk/ >>>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >>>> >>>> Darren Coombes >>>> Compositor >>>> >>>> www.resolutiondesign.com.au >>>> >>>> >>>> resolution: sydney australia tel: +61 2 9360 9908 fax: +61 >>>> 2 9360 8908 >>>> 22 burton st: east sydney: 2010 post office box: 614 darlinghurst: 1300 >>>> abn: 3305 196 1856 >>>> >>>> 2010 Silver One Show Entertainment Award: Online Branded Entertainment >>>> 2009 Gold Promax/BDA Award: Best Broadcast Design Image Spot >>>> 2009 Winner Creative Review Hotshop Award: Post Production / VFX >>>> 2009 Finalist Creative Review Hotshop Award: Broadcast Design >>>> >>>> >>>> The information transmitted, together with the attachments, is intended >>>> only for the person or entity to which it is addressed and may contain >>>> confidential and/or priviliged material which may be subject to copyright. >>>> Any review, retransmission or other use of, or taking of any action in >>>> reliance upon, this information by persons or entities other than the >>>> intended recipient is prohibited. If you received this in error, please >>>> contact the sender and delete the material from any computer or network. >>>> No warranty is given by the sender that any attachments to this email are >>>> free from viruses or other defects. >>>> >>>> >>>> <image.png> >>>> >>>> _______________________________________________ >>>> Nuke-users mailing list >>>> [email protected], http://forums.thefoundry.co.uk/ >>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >>> _______________________________________________ >>> Nuke-users mailing list >>> [email protected], http://forums.thefoundry.co.uk/ >>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >> _______________________________________________ >> Nuke-users mailing list >> [email protected], http://forums.thefoundry.co.uk/ >> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users > > _______________________________________________ > Nuke-users mailing list > [email protected], http://forums.thefoundry.co.uk/ > http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
_______________________________________________ Nuke-users mailing list [email protected], http://forums.thefoundry.co.uk/ http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
