Field of view tool

This is an excellent tool for showing the difference between different sensor sizes and how it affects the field of view. Wish there was one to show DoF too.

http://www.abelcine.com/fov/

Glidetrack Shooter SD

Just purchased a Glidetrack Shooter SD from Alistair @ www.glidetrack.com. I cannot recommend this product highly enough - it is simply an awesome piece of kit, especially when linked with the Manfrotto 577QR quick release place and Manfrotto 701HDV head.

Here are few videos I have shot with it recently:

http://www.vimeo.com/17981477

http://www.vimeo.com/17979791

http://www.vimeo.com/17953967

1/30s Shutter?

Due to the 180 degree shutter used in film cameras, the optimum shutter speed on a digital SLR should usually be around 1/2n where n = frame rate. For PAL 25fps therefore, the shutter should be 1/50s. If you shoot with a higher shutter than this, you can get very "staccato" looking images, especially during fast motion shots. However, what about shooting at the camera's minimum of 1/30s? The image might become too soft and there might be too much motion blur, however it's something I am going to try soon. The benefit of this is that for low light shooting, you can get away with a lower ISO or smaller aperture.....

Posted a demonstration video showing different shutter speeds at my Vimeo pages: www.vimeo.com/digitalvideoslr

DSLR CAMFRAME

Just bought a DSLR Camframe from B-Hague in Nottingham as shown here (without the camera which was taking the picture!). It provides side and top handles together with two additional hot shoe mounts (which I have used to mount my 126 LED light to one side, and HDMI field monitor / Zoom H4N to the other side).

Canon XLH1s vs. Canon 550D

Decided that in a few weeks time I am going to make a demonstration video comparing the differences / similarities of the Canon 550D SLR and the Canon XLH1s camcorder. I want to compare the DoF available with the same aperture on both. The Canon XLH1s, like many camcorders is around a x7 crop factor so I would have thought that with say an f1.8 aperture, the DoF is still going to be extremely deep. The plan is to film a tape measure from an angle so that the DoF can be measured and compared. The camcorder lens is a 5.5mm to 108mm "L" lens (equivalent to approx. 38mm to 778mm in 35mm format) and has a maximum f number of 1.6. Should be an interesting comparison.

Light tests

Have just taken delivery of 126 LED light. Will post a comparison video of it very soon when I get chance to make one!

Jamie's 30 Minute Meals

Just been watching a behind the scenes video of Jamie Oliver's new Channel 4 series and noticed that they were using a DSLR for some of the shots. Looked like the 70 to 200l f2.8 lens was being used in one of the shots. They also appear to be using RED ONE cameras too.

http://www.channel4.com/food/on-tv/jamie-oliver/jamie-s-30-minute-meals/index.html

LIGHT

Been looking at the Litepanels range of portable LED lights to sit on top of the camera. Their Micro Pro looks excellent but it retails for around £300!

I therefore visited eBay and after a bit of hunting around and review checking on YouTube, I have opted for the "CN-126" 126 LED light panel, which apart from being made from plastic, looks more or less the same as the Litepanels one. The best thing is that it retails for £37.50 and will take rechargeable camcorder batteries.

It also comes with a diffuser filter too and is totally dimmable.

Great Sound Design Website

I always like to show my students sound design / sound for picture "making of" documentaries as I think that they inspire students to start wanting to play with sound and go out and about acquiring sounds which they can later work with.

A student told me about this website yesterday and it simply is fantastic with lots and lots and lots of documentaries regarding sound design for films:

www.soundworkscollection.com

Tokina 11 to 16 f2.8

I think my next lens purchase will be the super wide Tokina 11 to 16 f2.8 lens. It doesn't seem to get a bad review anywhere and it's specially made for cropped sensors. On the 550D, the focal length will be around 18 to 26 which is still nice and wide.

Why a Crop Factor of x1.6 on APS-C sensors?

Just been reading around: (I think this is correct!)

http://en.wikipedia.org/wiki/Crop_factor [accessed 02/10/2010]

http://en.wikipedia.org/wiki/Charge-coupled_device [accessed 02/10/2010]

http://www.december.com/john/photography/cropfactor.html [accessed 02/10/2010]

to try and ascertain a good formula for calculating the crop factor between a full frame sensor and an APS-C sensor (used by 550D / 7D etc.).

The dimensions of a FULL FRAME sensor is 36mm x 24mm with a aspect of 3:2. Dimensions of an APS-C sensor is 22.7mm x 15.1mm, again with a 3:2 aspect.

Square root of (36^2 + 24^2) DIVIDED BY the square root of (22.3^2 + 14.9^2) = 1.6 approx.

This explains why the DoF on camcorders with such a small image sensor (6mm diagonal, 4.8mm x 3.6mm in the case of a 1/3" CCD), are so deep.

The crop factor of this 1/3" CCD sensor would be around x 7. Now, the ratio between each successive f stop is ROOT 2 or 1.414. Comparing a FULL FRAME f stop to an APS-C 1.6 crop shows that the difference in effective f number is around 1.13 fstops (i.e. 1.414 x 1.6). By this what I mean is that f4 on a FULL FRAME camera equates to f2.5 on a 1.6 crop. Now f2.8 would be ONE FSTOP wider, (i.e. 4 / 1.414) so f2.5 is slightly wide than this. Therefore, returning back to the previous example of a 1/3" CCD sensor with a crop factor of x7, how many effective f stops wider would the lens need to be to give the same DoF? Well, 7 / 1.414 = 4.95. Therefore, approx. 5 fstops wider! A 50mm lens with an f8 aperture on a FULL FRAME camera would therefore require 7mm lens with an f1.4 aperture to give approx. same DoF. If we took the same 50mm lens with an aperture of f2.8, we would need an aperture of f0.5???

The 1/3" example above doesn't have the same aspect ratio however, so the calculations will probably differ slightly :)

[Addition]: What about the difference between a x1.6 cropped sensor and 1/3" CCD? Well, as mentioned above, the dimensions of an APS-C sensor is 22.3mm x 14.9mm (diagonal of 26.7mm) and the dimensions of a 1/3" sensor is 4.8mm x 3.6mm with a diagonal of 6mm. Therefore, the crop factor between the APS-C and 1/3" is 26.8 / 6 = 4.55.

It would therefore seem that the effective change in f stops between these two sensors is 4.55 / 1.414 = 3.22 f stops. What this means is that f/8 on an APS-C camera would be the equivalent of a little over f2.8 on the 1/3". Also, to obtain the same field of view on the 1/3" camera, one would need to use a lens 4.55 times smaller (50mm lens, 35mm equivalent = 80mm on APS-C camera and 364mm on 1/3" sensor). So, to give same field of view, I would need to set the lens on the 1/3" camera to 80 / 4.55 = 18mm approx.

A test is going to be carried out to establish whether this is the case, by comparing both the field of view and Depth of Field between a 1/3" video camera and a Canon 550d (APS-C sensor). Watch this space!..... will place a demonstration video on Vimeo.

Here is an interesting article which shows some example shots taken with two different sensor sizes and it sort of agrees with what is being said here:

http://www.janrik.net/DOFpostings/PM1/Depth_of_Field_Versus_Sensor_Size.html [ accessed 14/11/2010].

The crop factor between the two cameras is x3.07. To obtain the same DoF on both sensors, one needed to be set to f/4 and the other f/13. This is very interesting as this represents a little over 3 f stops difference (i.e. f/5.6, f/8, f/11 and a bit more to f/13). The focal length must also have been set to 3.07 times shorter too, although it doesn't stage this in the article. My theory that that the change in f number is equal to the crop factor / divided by 1.414 doesn't therefore ring true here, so it will be interesting to see what my test demonstrates.

[EDIT - 10/01/2010] - JUST FOUND THIS AWESOME FIELD OF VIEW CALCULATOR / DEMONSTRATION TOOL:

http://www.abelcine.com/fov/

DAM - Digital Asset Management

There's not really a right or wrong answer to "looking after" all of the assets which make up a project, but the need for a decent asset management strategy, especially when using double system sound is very important. Students often run into problems when moving from one edit suite / studio to another, and often leave some of their files behind. I have therefore created a basic flow chart which discusses a solution (not THE solution) to help make asset management easier.

This video http://www.vimeo.com/14840608 which I thought was excellent, runs through some really useful methods; my flow chart is attached here too, with a couple of extra stages added if necessary, such as setting up the scratch disc and exporting to ProTools for further sound editing .... (please click on the picture to open it and so that you can read it properly).

The flow chart (and video) makes use of Final Cut's MERGE CLIP feature when using double system sound and this has been discussed and demonstrated on this Blog previously. Equally, PLURALEYES could be used for the automatic sync'ing of clips if a clapperboard of some kind of sync point was not used......

First Electronic Viewfinder for DSLR

Redrock micro have jsut announced the world's first HDMI electronic viewfinder for HDSLR cameras:

http://www.dslrnewsshooter.com/2010/09/26/redrock-micro-launches-the-microevf-for-hddslr/

Monopod

Went out with the camera this morning to a local nature reserve to have a further play with my new 70 to 200L f4 lens. However, this time I also took a monopod and what can I say, these things are great and help take the weight incredibly well. When normally holding the camera with the lens at its maximum focal length, it's so tiresome to hold it steady; not with the monopod!

Great!

Audio drifit issues

Found a very interesting article here discussing a "glitch" in Final Cut Pro which sometimes can cause separate audio to start drifting from the picture:

http://brucesharpe.blogspot.com/2009/06/dslr-dual-system-audio-999-solution.html

I intend to make a demonstration video discussing this shortly.....

ZOOM H4N Output Level Settings

Carried out a little test the other day to compare the output levels of the Zoom H4N when input to the Canon 550D. The audio output is on its own too "hot" for the 550D to handle and as the 550D has no gain controls for its audio input, a PAD cable needs to be employed. Luckily Pink Noise Systems manufacture a custom mini jack to mini jack cable with built in -25dB attenuator to prevent the input on the 550D from overdriving. I wondered however what effect changing the audio output level on the Zoom H4N would have.

With the audio output on 50 (i.e. half way), there was quite a lot of noise present, but compared to a setting of 75 and 100, it sounded far more transparent without any nasty AGC (automatic gain control) kicking on the Camera. I am not interested in keeping the audio any way as I would use separate sound recorded by the Zoom any way, it's just that I wondered how the quality of the audio recorded by the camera would be affected.

Results here: http://www.vimeo.com/15159957

Zoom H4N Limiter Settings?

Just been playing around with the three different LIMITER settings on the ZOOM H4N. The manual doesn't give any information as to what level the limiter actually kicks in at, so I decided to quickly test the three. It appears that on "LIMIT 1" it kicks in at around -9dBFS, "LIMIT 2" at around -6dBFS and "LIMIT 3" at around -3dBFS. I think to try and keep recordings as transparent as possible, I will therefore use LIMIT 3 from now on. Recording at 24 bits, it is not necessary to get as close to 0dBFS as possible, so as long as sufficient headroom is left, the limiter at this level should very rarely kick in; only when the signal is getting very close to 0dBFS....

Sensor Size vs. Depth of Field

Just had a thought - yes, the sensor size does affect the camera's field of view, but does it also have an impact on its depth of field?

Let's take a 35mm camera (such as the Canon 5D MKII) which has a full frame sensor. If we stick on an 80mm lens set with an aperture of f/4, then the diameter of the iris at this setting would be 80mm / 4 = 20mm. However, with a cropped sensor of 1.6, the same effective field of view would be obtained from a 50mm lens (i.e. 80mm / 1.6 = 50mm). Therefore, with this, the diameter of the iris, again at f/4 would only be 12.5mm, i.e. smaller than for the uncropped sensor. So, to obtain the same aperture diameter of 20mm, the f number would need to be 50mm / 20mm = f/2.5 which is more than one f stop larger.

Looking at it another way, if the aperture of 80mm lens on the 35mm camera was set to 12.5mm (i.e. the calculated diameter of the 50mm lens on the cropped sensor), its f number would only need to be 80 / 12.5 = 6.4.

Or putting it another way, the equivalent f number rises or falls by a factor equal to the SQUARE of crop factor:

f/4 on 1.6 cropped sensor = f/2.5 on full frame

f4 on full frame sensor = f6.4 on 1.6 cropped sensor.

This is very interesting as it means that to get the same depth of field that say a 50mm f1.4 lens would give on a full frame sensor, one would need a 31mm lens with an aperture of approx. f0.55 (1.4 / 1.6^2)!

It can therefore be seen that using a full frame camera yields not only a change in the field of view, but also a decrease in the depth of field.

The Road to Coronation Street

Found an interesting article discussing the recent BBC4 Drama "The Road To Cornoration Street" in that it was mostly shot on the Canon 5D MKII Digital SLR:

http://www.4khub.co.za/node/82

Final Cut Issues

Spent an age today trying to compile a demonstration video whereby some footage was 1080p ProRes from the Camera and others were MP4 screen grabs from Quicktime Player X. Firstly, I was unable to get the screen grab footage to load into Final Cut Pro, so I tried transcoding it to ProRes and HDV but neither of these would still load into FCP? Any way, eventually, after using EXPORT TO DV within MPEGStreamClip, I managed to get some footage to load. However, I didn't realise until after several exports of the finished edit, that my sequence preset had been set to PAL DV 720 x 576 due to the format of some of the clips being brought in. This was fine, or so I thought, because I could simply amend the sequence preset from within the settings window. After having changed the sequence preset back to ProRes(LT) 1080p 25fps, the strangest thing happened to all of my footage in that its dimensions drastically reduced, even for the native 1080p footage from the camera? To cut a long story short, the only way to get round this was to re-add each of the pieces of footage back onto the sequence? Very strange??