21" 2015 Retina imac for 4k video?

Discussion in 'iMac' started by nph, Nov 10, 2015.

  1. nph macrumors 6502a

    Feb 9, 2005
    I have been waiting for a 21" 4k retina iMac for a long time. Now when it finally comes there is no option of a dedicated graphic card. For games, it really doesn't matter, only interested in WoW playing anyway but my main area for getting it is 4k video editing.
    Can it handle that? Would i7 processor upgrade/16Gig RAM help?
    I will go for 256 SSD and use external drive for storage.

    Appreciate any insight you can provide since I really like the size and screen but I need the performance and do I have to go for the 27" version to get that?

  2. schloerg macrumors newbie


    Aug 31, 2011
  3. fathergll macrumors 65816

    Sep 3, 2014
    What exactly are you editing? 4K is a vague term.
  4. AppleHater macrumors 6502a

    Jun 9, 2010
    Unfortunately it's not a black answer you can get out of it in this case. As a guy who had the same question, I came to the conclusion that what my expectations will answer the question.

    Obviously 12 core MacPro with dual GPU will easily beat 27inch top of the line iMac handling 4K video. But that doesn't mean everyone needs the MacPro. If you're not working on lengthy feature videos all the time and rather short 2-3 minute clips for family, moderate setup will get you what you need; just slower.
  5. Sirmausalot macrumors 6502a


    Sep 1, 2007
    probably not. but we need more information (codecs, length of project, editing software) to help you male an informed decision. i think the 395 is the minimum needed for 4k
  6. nph thread starter macrumors 6502a

    Feb 9, 2005
    I am looking at Final Cut Pro and 4K video from a Sony A7. Home videos not professional and as long as it is not dirt slow it would be sufficient.
    Does this help?
  7. joema2 macrumors 68000


    Sep 3, 2013
    I shoot and edit lots of 4k with the A7RII and other cameras. 4k is just very demanding from both CPU and space standpoints. This should make sense -- it is 4 times the data of 1080p.

    A big advantage of FCP X is the built-in seamless proxy workflow. On import or afterward you can transcode your 4k media to proxy, then in the upper-right of the viewer select "view proxy", and all subsequent editing and viewing will automatically be on the proxy files which are 1/4 the resolution (1/2 the X&Y linear resolution). Then before your final export just remember to select "view optimized/original" and it will automatically use all your edits on the original res files. It is seamless, requires no management and is very reliable.

    This enables lower-horsepower computers to have a chance at editing 4k. On my top-spec 2015 iMac 27, I can get by without using proxy on short single-stream 4k videos, but it can be a little laggy for rapid "JKL" editing. For multicam, proxy is a necessity.

    Proxy files take up additional space -- I'd estimate about equal space to the original camera native files. Even though the resolution is lower, they are ProRes files so are much less compressed. So you must have enough storage for these.

    A good 3rd party tool to help manage FCP X space is Final Cut Library File Manager: http://www.arcticwhiteness.com/finalcutlibrarymanager/

    I would personally recommend a higher-end Mac. You might be able to take a 4k clip to your Apple Store and try it on an iMac with FCP X to get a feel for the performance.
  8. Sirmausalot macrumors 6502a


    Sep 1, 2007
    Almost. The A7 R or S or RII? Either way, it takes a lot of horsepower to push those pixels around. Premiere will let you edit at 1/4 resolution and as joma said, Final Cut will work with proxies. But if you are truly working 4K end to end, you are talking a huge amount of cash in camera, possibly recorder, and perhaps a 4K TV to screen it on. We're not in home movie territory.

    So if your budget is that constrained, then I'd suggest shooting in 1080P and working on the 21" iMac -- which is great for home movies. You'll get a great picture and be able to share with family and friends who probably don't have 4K capabilities. But if you are going to work with 4K from a Sony camera, you need the beefiest iMac you can get with an i7 and a 395(x). Otherwise you'll not only be frustrated, you'll be wasting your time working with 4K.

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7 November 10, 2015