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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old August 12th, 2010, 12:52 AM   #1
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Best way to ensure focus

Hi

I have been playing arround with my fairly new T2i with video. I find it sometimes a bid hard to ensure that the picture is properly in focus.
I have read about 6-8" HDMI monitors on top and the Z-finder. Which solution is best, and does any have pros and cons about thoose two, and perhaps there are other options as well?

Thanks.

/Ulf
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Old August 12th, 2010, 02:29 AM   #2
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If its a set shot and you do not have to refocus then you can zoom in x5 or x10 in the live view mode before hitting record. Much more precise then using either of the other 2 options imo.

Last edited by Sam Tansey; August 12th, 2010 at 02:30 AM. Reason: edit
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Old August 12th, 2010, 03:48 AM   #3
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Don't forget the One-shot Auto Focus.
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Old August 12th, 2010, 03:59 AM   #4
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Quote:
Originally Posted by Ulf Laursen View Post
Hi

I have been playing arround with my fairly new T2i with video. I find it sometimes a bid hard to ensure that the picture is properly in focus.
I have read about 6-8" HDMI monitors on top and the Z-finder. Which solution is best, and does any have pros and cons about thoose two, and perhaps there are other options as well?

Thanks.

/Ulf
The problem with an external monitor vs a loupe/z-finder is that the camera only outputs 480p while recording. The LCD has great resolution, so it is superior for critical focus work. Therefore a loupe is the best option for focus while recording.

I agree that the x5/x10 magnification option is a very accurate way of working, but as you say, only prior to taking a shot.

I read somewhere, I think from Tramm, that there is a proposal for magic lantern for picture in picture magnified focus assist during record, where the main view is the magnified section and a PIP window shows the un-magnified view for keeping the shot in frame. If this ever happens, I think this option with a loupe would make focus really easy.
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Old August 12th, 2010, 06:42 AM   #5
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Originally Posted by James Donnelly View Post
The problem with an external monitor vs a loupe/z-finder is that the camera only outputs 480p while recording. The LCD has great resolution, so it is superior for critical focus work. Therefore a loupe is the best option for focus while recording.
The resolution of the LCD screen is 720x480 pixels & a loupe just enlarges the pixels.
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Old August 12th, 2010, 09:36 AM   #6
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No, the resolution of the LCD on the 550d is 1,040,000 pixels in a ratio of 3:2

720 x 480 = 345600

It's roughly 1248 x 832

ratio (w/h) = 1.5
Resolution = 1040000

h = root(Resolution/ratio) = 832

See the spec:

Canon EOS 550D - EOS Digital SLR Camera - Canon UK

Besides, a quick look at the lcd with a loupe, and you can clearly see it is not 480 lines.
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Old August 12th, 2010, 10:23 AM   #7
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Thanks a lot guys :)

/Ulf
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Old August 12th, 2010, 11:55 AM   #8
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One other focus related consideration is DOF. Obviously it's going to be harder to focus at f1.8 than at f5.6 since the DOF is so much shallower. I find myself spending a lot of time checking DOF meters - I've got one on my iPhone now.
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Old August 13th, 2010, 11:01 AM   #9
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Quote:
Originally Posted by James Donnelly View Post
No, the resolution of the LCD on the 550d is 1,040,000 pixels in a ratio of 3:2

720 x 480 = 345600

It's roughly 1248 x 832

ratio (w/h) = 1.5
Resolution = 1040000

h = root(Resolution/ratio) = 832

See the spec:

Canon EOS 550D - EOS Digital SLR Camera - Canon UK

Besides, a quick look at the lcd with a loupe, and you can clearly see it is not 480 lines.
Not so. The Canon specifications rather disingenuously refer to a resolution of 1.04 million dots That is not pixels. Each LCD pixel includes three individual colored dots (red, green and blue - RGB). The screen resolution is 720 x 480 x 3 RGB dots making for a total of about 1.04 million dots.

I don't have a T2i/550D but looking through a loupe at the screen on my 5D Mk II (640 x 480 x 3 = 920,000 dots) I can clearly see the pixels. The pixel density on both screens is similar. Here is a link to Canon's rather more honest specifications for the 5DII LCD screen where it is referred to as VGA resolution i.e. 640x480 but 920,000 dots
Canon Digital Learning Center - EOS 5D Mark II
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Old August 13th, 2010, 03:48 PM   #10
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I see. Well it seems I have fallen hook line and sinker for Canon's skulduggery. Doh!

It is very useful to be set straight on this as I may now consider buying a decent external monitor, so thank you for taking the time Nigel.
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Old August 13th, 2010, 05:14 PM   #11
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The Z-Finder is the best solution I have found. As mentioned above...when I use my SmallHD monitor, it's great for setting a shot but once you hit record, it down-res's the picture. Once you get used to the loupe, i's pretty easy and using a follow focus becomes a lot of fun. BUT like everything that doesn't have a computer to help you, it will require effort to develop the skill.

Did a shoot with the T2i on the shoulder mount with a FF yesterday and it's great, crisp footage. Not so with my initial attempts when I first got the camera.

The other secret for getting focus right is you don't always need a 3" DOF. Bump the aperture up to 5.6 or more and your DOF will be much easier to use. When I fly the T2i on my Blackbird, this is the only way to get good focus as the camera can't be adjusted once you're moving.

This link helped me quite a bit...

Online Depth of Field Calculator
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Old August 13th, 2010, 09:22 PM   #12
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Quote:
Originally Posted by Nigel Barker View Post
Not so. The Canon specifications rather disingenuously refer to a resolution of 1.04 million dots That is not pixels. Each LCD pixel includes three individual colored dots (red, green and blue - RGB). The screen resolution is 720 x 480 x 3 RGB dots making for a total of about 1.04 million dots.

I don't have a T2i/550D but looking through a loupe at the screen on my 5D Mk II (640 x 480 x 3 = 920,000 dots) I can clearly see the pixels. The pixel density on both screens is similar. Here is a link to Canon's rather more honest specifications for the 5DII LCD screen where it is referred to as VGA resolution i.e. 640x480 but 920,000 dots
Canon Digital Learning Center - EOS 5D Mark II
IMO, a 3X Loupe like Zacuto's makes it hard to focus as one sees the pixels too large. I use a 1X Hoodman loupe and critical focus is quite easy. That said, it could be that my glasses (left on while viewing) are what is magnifying things larger than needed, although results seem similar to me when I try viewing w/o glasses and use dioptor.
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