The way the coax cables used for SDI works is very different to the way an HDMI cable works. HDMI cables are indeed constructed quite differently between early HDMI 1.0 – 1.4 classes and the more recent 2.0+ classes. So with HDMI you will find that an old, early version HDMI cable won’t work with the latest standards.
SDI cables are nothing fancy.
SDI uses nothing more sophisticated than a single core coax cable that is no different in it’s basic design, construction and mode of operation to an ordinary TV aerial down lead. It is a very simple type of cable and really nothing fancy.
The SDI signal is very high frequency; in effect it is a radio signal. From a cabling point of view the ONLY difference between the original SDI standard and the latest standards is the frequency. The way the cable works is no different between the original SDI standard and the latest and a camera or monitor has no way of telling or knowing what type of cable you are using.
Frequency is important because the higher the frequency, the more lossy ANY coax cable will become (leaky kind of describes what’s going on). Low quality cable – more signal leaks out, high quality cable less leaks out so the signal will go further.
But even the very earliest SDI cables were normally made using good quality very low loss coax. These original SDI cables are perfectly capable of carrying the higher frequencies used by 12G SDI. BUT over very long lengths there will be more loss at 12G than at 1.5G.
It’s not the “G” that counts, it’s the quality.
So really when looking for SDI cables, the question isn’t – “is it 12G” the question should be “what are the cable losses” or more simply “is it a good quality cable”. There are plenty of original SDI cables that can be used at 50m at 12G without issue. At the same time I have also seen cables marketed as “12G” that are nowhere near as well screened, with much higher losses, that barely work at 10m.
Just as important as the cable losses is the construction. Have the connectors been fitted correctly? Are the connectors correctly sized for the cable that’s being used, has the crimping or soldering been done well? Most coax cable failures are due to poor connector assembly or the use of low-quality connectors.
One other thing to watch for is the cable impedance. SDI cables should be made using 75 ohm impedance cable and connectors. Radio cables for radio communications normally use 50 ohm cables and connectors and the two are not really compatible. But often cheaper cables sold for SDI and video applications may be made using 50 ohm parts as often these are cheaper. These cables will fit and more often than not they appear to work. BUT the pins in the BNC plugs are a different size and this can result in intermittent connections and over time can even damage the connectors on cameras and monitors etc. So do make sure your cables really are 75 ohm.
In the real world:
For most shorter cables, up to 5m cable losses are rarely an issue unless the cable is of particularly low quality or badly made. For between 5m and 10m you should avoid the very thin coax cables as the losses become more significant. Above 10m use only low loss cables with good quality screening. A cable sold as a “12G” cable should indicate good quality low loss cable, but it is not a guarantee. And the vast majority of well-constructed normal SDI cables will work just as well unless you want extremely long runs in which case you need ultra-low loss cable.
The FX6’s CineEI mode is designed to make shooting using S-Log3 or raw easy and straightforward. It optimises the camera so that settings such as the recording ISO, noise reduction and sharpening are all optimised for recording either S-Log3 or raw with the best possible dynamic range.
It also makes sure that the S-Log3 or raw recordings are optimised for grading. In addition you can use a LUT (Look Up Table) in the viewfinder or on the HDMI/SDI output to provide an approximation of how your footage will look after it’s been graded as well as to assist you in getting the exposure right.
HINT: What is a LUT? A LUT is a simple Look Up Table of input values that represent different levels in the recording format (in this case S-Log3) and then converts those input values to new output values that are appropriate for the monitor or display range you are using. This conversion can included stylised adjustments to give the output image a specific look.
Once you have a LUT enabled and you are viewing the LUT either in the viewfinder or on a monitor an exposure offset can be applied to the LUT to make it darker or brighter than normal. This LUT brightness offset is used to allow you to deliberately offset how bright the recordings are, this is the “EI” or Exposure Index part of CineEI. More on that later.
BUILT IN LUTS
The FX6 has 3 built in LUTs, but in addition to the built in LUTs you can load your own “user LUTs” into the camera as what the FX6 calls “Base Looks” making this a very flexible and capable system. If you want to load you own LUTs into the camera these must be 3D Cube LUT’s and should be placed in the — Private : SONY : PRO : LUT folder of an SD card or CFExpress card that has been formated in card slot 2 of the FX6. The LUT’s should be 17x or preferably 33x cube LUT’s designed for use with S-Log3 and SGamut3.cine. They are loaded via the main menu PAINT – BASE LOOK page.
As your material will require grading in post production, if you are shooting UHD or 4K you should NOT use XAVC-L because in UHD/4K XAVC-L is 8 bit 4:2:0. A much better choice is XAVC-I which is always 10 bit 4:2:2 and/or raw.
FIXED RECORDING ISO.
Once the camera is set to use the CineEI mode the recording sensitivity is fixed to either 800 ISO when in Lo Base sensitivity or 12,800 ISO when the camera is set to Hi Base sensitivity. These values cannot be changed and your recordings will always take place at one of these sensitivity levels.
ENABLE A LUT.
To take full advantage of the Cine EI mode the next step is to enable a LUT for the viewfinder and also optionally for the HDMI and SDI outputs.
The default LUT is Sony’s s709 LUT. This is the same LUT as used by the Venice digital cinema camera. s709 is designed to be a starting point for a film style look. To achieve this film style look it uses brightness levels more commonly found in feature films rather than the levels normally used in the majority of regular TV shows.
LUT EXPOSURE LEVELS
There are some important things to understand about different LUTs and Base Looks. Each LUT/Look will have it’s own optimum brightness levels. They will not all be the same. Some will be brighter or darker than others when exposed correctly, so it’s vital that you understand what levels any LUT that you chose to use needs to be exposed at.
Another LUT that the FX6 includes is Sony’s 709(800) LUT. This LUT is more closely aligned with the levels used in normal TV productions, so it looks very different to s709 and has very different brightness levels when exposed correctly.
The chart below gives the “correct” exposure values for S-Log3 as well as some guide values based on my own measurements for the s709 and 709(800) LUTs in the FX6.
Average Skin Tones
90% Reflectivity white card (add 2-3% for white paper).
MEASURING THE EXPOSURE.
There are many ways to measure your exposure when shooting using S-Log3 and LUT’s. You could choose to use a light meter, in which case the light meter would be set to match the EI (Exposure Index) value set in the camera. You can just look at the image in the viewfinder and judge when it looks right. Most of the time this is OK, but it isn’t particularly accurate. My prefered method is to use a white card or grey card and then use the cameras built in video signal monitor and the waveform display to actually measure the brightness of the grey card or white card.
If you are not familiar with a waveform display it actually really easy to understand. The bottom of the waveform is black and the very top is 109%, the brightest that the camera can ever record to. The left hand side is the left of the video image and the right is the right of the video image. The thin reference lines across the waveform display are at 0% (the darkest a video image should ever normally be), 25%, 50%, 75% and 100%.
In addition the FX6’s waveform display includes 2 yellow lines. The position of these yellow lines is determined to the levels that the cameras zebras are set to. By default the lower yellow line will be at 70% to match Zebra 1 and the upper line at 100% to match zebra 2.
MEASURING THE EXPOSURE.
The waveform display measures the signal that is on the HDMI and the SDI output. So once you have turned on the LUT for the HDMI/SDI it is the levels of the LUT that is being measured. What the waveform is measuring is indicated just above the waveform display.
To make it easier to understand how CineEI works and to show you how I like to have my FX6 setup, I find it easier to start off by turning OFF the LUT for the SDI and HDMI and measuring the exposure of the S-Log3. If you do this when the the Exposure Index (EI) is equal to the Recording or Base ISO then we can establish the correct exposure for the S-Log3 using a white card or white piece of paper and then also check the exposure of the LUT.
FIRST CHECK AND SET THE EXPOSURE INDEX LEVELS.
With the cameras base ISO set to low / 800 ISO I recommend that you set the EI levels in the main menu SHOOTING – ISO/Gain/EI as follows:
When using the CineEI mode you can change the EI several ways. The most commonly used ways will likely be via the L/M/H ISO/Gain switch or by pressing the ISO/Gain button and then using the multi-function dial (MFD) to change the EI. Do note that when you use the multi-function dial or Direct Menu to change the EI this new EI setting changes the preset value associated with the current position of the L/M/H switch.
I do not set an Exposure Index higher than the base recording ISO. The reason for this is that if you record using a high EI value your images will be noisy and grainy and could be very difficult to grade. Because you don’t ever see your final results until you get into post production, if you accidentally record noisy log you won’t really know how bad the footage will be until it is perhaps too late to do anything about it. So I set the EI for the Low Base 800 ISO as H>800EI, M>400EI, L>200EI. The difference between each of these EI’s is one stop and that makes it easier when you are checking any exposure changes.
For the 12,800 High base ISO I set the EI to H>12800EI, M>6400EI, L>3200EI.
FOR THIS EXAMPLE START AT LOW BASE/800 ISO and 800 EI.
By using the same EI as the base recording ISO there will be no offset or difference between the correct exposure for the LUT and the correct, or base exposure for the S-Log3. Expose the LUT corrrectly and the S-Log3 will be also be normally exposed. Expose the S-Log3 normally and the LUT will look correct.
FOR THIS EXAMPLE LET’S START WITH THE SDI/HDMI LUT OFF.
For this example I am going to start with the LUT OFF for the SDI and HDMI, this way the waveform display will be measuring the S-Log3. Just above the waveform it should say SG3C/Slog3, telling you the waveform is measuring the S-Log3.
Referring to the table of exposure levels above we can see that the correct S-Log3 exposure for a white card (90% reflectivity white) is 61% – if using a normal piece of printer paper I suggest using a value a little higher (around 63%) as white paper tends to be a little brighter than a proper white test card.
SETTING ZEBRA 1 TO 61%
To make finding where 61% is on the waveform I recommend setting Zebra 1 to 61% so that the lower of the two yellow zebra lines is at 61%.
So now when checking the exposure of a white card when the waveform is measuring the S-Log3 it is simply a case of adjusting the exposure until the white card is at the same level as the 61% line. Alternately you could use an 18% grey card, in which case you would set Zebra 1 to 41%, however there are often times when I forget my grey card but I almost always have a piece of paper somewhere.
So now we know the S-Log3 is correctly exposed lets turn ON the LUT for the SDI and HDMI outputs and check the exposure level of the s709 LUT.
TURN ON THE LUT.
And if we refer to the exposure chart given towards the top of the page we will see that white for the s709 LUT is 77%. So now let’s set Zebra 2 to 77% to make 77% easier to find on the waveform. Do remember however that other LUTs may need different levels, 77% is just for s709, 709(800) would require Zebra 2 to be set to 89%.
SET ZEBRA 2 TO 77% FOR s709
Now with the LUT ON for the SDI/HDMI we should see the brightness of the white card line up with the upper yellow line that represents Zebra 2 and 77%.
As you can see from the above example when the Base ISO and Exposure Index are matched, when the LUT for the SDI/HDMI is OFF and the white card is at 61% on the waveform the S-Log3 is correctly exposed.
Then when the s709 LUT is ON for the SDI/HDMI and the white card is at 77% we are correctly exposed. By having Zebra 1 set at 61% (for S-Log3) and Zebra 2 set for the white level for for your chosen LUT we can check either simply by turning the HDMI/SDI LUT ON or OFF.
USING THE 709(800) LUT INSTEAD
If you want a more contrasty looking image in the viewfinder and similar brightness levels to other video cameras – for example skin tones around 70% you might prefer to use the 709(800) LUT. When using the 709(800) LUT to measure a white card you should set Zebra 2 to 89%. It’s also worth noting that with the 709(800) LUT, if you wish, you could just leave the zebras at their default settings with Zebra 1 at 70% where just like a conventional Rec-709 video camera they will appear over brighter skin tones when viewing via the LUT.
CHANGING THE EXPOSURE INDEX TO OFFSET THE LOG EXPOSURE.
Sometimes it can be desirable to expose the S-Log3 a little brighter. For example when shooting scenes with a low average brightness level or scenes with large areas of shadows. The FX6 has very low noise levels at 800 ISO base. So for most scenes with higher average brightness levels there is no need to expose the log brighter. But there is a bit more noise at 12,800 ISO base. As a result it can be beneficial to expose the S-Log3 a bit brighter when using 12,800 ISO base.
The CineEI mode makes this very easy to do in a very controlled manner. Keeping the amount of over exposure constant helps speed up the grading process as all your material can be graded in exactly the same way.
Over exposing or underexposing Log does not change the captured dynamic range, it will always be the same. However exposing log brighter will reduce the highlight range while at the same time increasing the shadow range. A brighter exposure will result in less noise after grading.
Exposing log darker will increase the highlight range but decrease the shadow range. A darker exposure will result in more noise after grading. Because under exposed log can become very noisy, very quickly I do not recommend under exposing log, because of this I strongly advise against ever using an EI that is higher than the base ISO as this will result in under exposed log.
CHANGING THE EI ONLY CHANGES THE LUT.
When you change the Exposure Index the only thing that actually changes is the brightness of the LUT. So for EI to work you must be monitoring via a LUT.
Below is what happens to the image in the viewfinder when you have a LUT enabled (s709 in this case) and you lower the EI from 800 EI down to 200 EI in 1 stop steps and make no changes to the exposure.
As we have not changed the exposure in any way, the only thing changing is the brightness of the LUT. The recording levels have not yet changed in any way.
BUT NOW WE CHANGE THE EXPOSURE
Because the image in the viewfinder is now dark and the white card no longer reaches the correct exposure for the LUT, we now adjust the exposure. In this example I simply opened the aperture by 2 stops from f8 to f4 to match the 2 stop change in the LUT brightness. Now the image in the viewfinder looks correct again and the white card is meeting the upper yellow line again (77% as set by Zebra 2 level).
BECAUSE THE EXPOSURE IS BRIGHTER THE S-LOG3 IS NOW ALSO BRIGHTER.
Because I have opened the aperture by 2 stops to make the 200 EI LUT exposure look right the S-Log3 recordings will now be 2 stops brighter. If I turn off the LUT for the SDI/HDMI we can see that the S-Log3 is much brighter 2 stops brighter like this, the S-log3 white card level becomes 79%, so it appears slightly above the 77% Zebra 1 line.
Buy making the LUT darker by 2 stops, then adjusting the exposure upwards 2 stops to return the LUT to the original brightness we have made our recordings 2 stops brighter. This is how you use CineEI to alter the brightness of your recordings.
At Low base ISO (800 ISO) the FX6 is a low noise camera, so there is no need to routinely over expose the log as there is with more noisy cameras like the FS5 or FS7. So I normally shoot at 800 EI. When using the high base ISO or 12,800 ISO there is a bit more noise and when using high base I will typically set the EI to 6400 EI as the 1 stop brighter recordings that this will result in helps compensate for the increased recording noise.
In the examples given here I have used a white card to set the exposure. This is accurate and highly repeatable. But there will be times where you may not have a white card. At these times CineEI can still be used either by setting the Zebras to the appropriate skin tone levels for the chosen LUT (see the table towards the beginning) or by carefully “eyeballing” the brightness of the LUT image – if it looks right, it probably is right. If you are eyeballing it I highly recommend a deep sunshade or other device to exclude as much light as possible from the viewfinder.
CLIP PLAYBACK QUIRKS
One great FX6 feature is that when you play back clips in the CineEI mode the camera can apply a LUT to the clip. Simply enable the LUT you want o use as you would when shooting. BUT currently the FX6 applies an EI offset that you have assigned to the L/M/H gain/ISO switch back to front!!!
REVERSED CINE-EI PLAYBACK OFFSET CAUTION!!!
For example: You set the L/M/H gain/ISO switch so that the EI offsets are H = 1600 EI, M is 800 EI and L is 400 EI. Then you set the switch to L and 400EI. Because you are shooing at 400 EI the recordings you will make will be 1 stop brighter than “normal”. This can be very handy to really minimise noise in your recordings.
Then you go into Thumbnail mode to play back your clips. You would expect/hope that if you were to leave the L/M/H switch where it was in the “L” position that the clip would look the same as it did when you were shooting. BUT IT DOESN’T THE CLIP LOOKS WRONG! The clip would actually look 2 stops brighter than it should.
I don’t understand why the FX6 behaves like this, but an EI offset applied to the L/M/H switch is applied the wrong way on playback. To make make a clip shot at 400 EI look correct on play back you need to set the switch to the H or 1600 EI position then it will look right.
I believe this is a bug, or perhaps a firmware limitation. But as a work-around I suggest setting the offsets for the L/M/H switch as 400/800/1600 EI this way you can shoot at 400 EI then play back the clips with the switch flipped to 1600 and the clip will look correct. Similarly you can shoot with the switch set to H and 1600 EI (not something I recommend) and then play back the clips with the switch flipped to L and the clips will look as they did when you were shooting.
HOWEVER YOU DO THIS BE AWARE THAT THE L/M/H Gain switch alters the brightness of the clips when played back via a LUT. The only time there is no playback offset is when the switch is set to 800EI. So make sure you understand what it is you are looking at when playing back clips in CineEI.
Changing the way the camera looks and using LUTs in Custom Mode:
You can also use any user LUTs that you have loaded into the camera to alter the base look when you are shooting in custom mode. For more information on that please watch the video below.
Maybe it’s just because I’m getting old, but I do like to have a label to remind me of what I have assigned to the assignable buttons on my cameras.
There are lot’s of ways you can make a label from a post-it-note to camera tape. But I recently got a new label printer from Dymo and with the right tape it will print white text on clear tape. The printers are around $40 so they are not too expensive. If you’re anything like me once you get one you will find yourself labelling everything, so a worthwhile investment.
For the labels on my FX9 I used the smallest “8” point text size and you will need to trim the labels down with a sharp pair of scissors. They need to be very small to fit in the gaps between the buttons. I found a pair of tweezers really helps to hold the label while you cut it and peel of the backing. Then you can use the tweezers to place your swanky new label exactly where you want it.
I think they look pretty good and are worth the effort. The printer I used is a Dymo Label Manager 160 and the tape is a Office Depot white on clear 12mm plastic tape. There are lots of colour choices if you don’t want clear tape. Looking at the pictures of the camera I now realise I should have taken a bit more time to get the labels straight! Fortunately you can peel them off without leaving any nasty residue or damaging the paint.
I see it so many times on various forums and user groups – “I didn’t see it until I looked at it at home and now I find the footage is unusable”.
We all want our footage to be perfect all of the time, but sometimes there might be something that trips up the technology that we are using. And that can introduce problems into a shot. The problem is perhaps that these things are not normal. As a result we don’t expect them to be there, so we don’t necessarily look for them. But thinking about this, I also think a lot of it is because very often the only thing being used to view what is being shot is a tiny LCD screen.
For the first 15 years of my career the only viewfinders available were either a monocular viewfinder with a magnifier or a large studio style viewfinder (typically 7″). Frankly if all you are using is a 3.5″ LCD screen, then you will miss many things!
I see many forum post about these missed image issues on my phone which has a 6″ screen. When I view the small versions of the posted examples of the issue I can rarely see it. But view it full screen and it becomes obvious. So what hope do you have of picking up these issue on location with a tiny monitor screen, often viewed too closely to be in good focus.
A 20 year old will typically have a focus range of around 12 diopters, but by the time you get to 30 that decreases to about 8, by 40 to 5 and 50 just 1 or 2. What that means (for the average person) is that if you are young enough you might be able to focus sufficiently on that small LCD when it’s close enough to your eyes for you to be able to see it properly and be able to see potential problems. But by the time you get to 30 most people won’t be able to adequately focus on a 3.5″ LCD until it’s too far from their eyes to resolve everything it is capable of showing you. If you are hand holding a camera with a 3.5″ screen such that the screen is 30cm or more from your eyes there is no way you can see critical focus or small image artefacts, the screen is just too small. Plus most people that don’t have their eyesight tested regularly don’t even realise it is deteriorating until it gets really bad.
There are very good reason why viewfinders have diopters/magnifiers. They are there to allow you to see everything your screen can show, they make the image appear larger, they keep out unwanted light. When you stop using them you risk missing things that can ruin a shot, whether that’s focus that’s almost but not quite right, something in the background that shouldn’t be there or some subtle technical issue.
It’s all too easy to remove the magnifier and just shoot with the LCD, trusting that the camera will do what you hope it to. Often it’s the easiest way to shoot, we’ve all been there I’m sure. BUT easy doesn’t mean best. When you remove the magnifier you are choosing easy shooting over the ability to see issues in your footage before it’s too late to do something about it.
The Sony PXW-Z90 is a real gem of a camcorder. It’s very small yet packs a 1″ sensor , has real built in ND filters, broadcast codecs and produces a great image. On top of all that it can also stream live directly to Facebook and other similar platforms. In this video I show you how to set up the Z90 to stream live to YouTube. Facebook is similar. The NX80 from Sony is very similar and can also live stream in the same way.
In case you missed the live stream I have uploaded the recording I made of my almost hour long video with hints, tips and ideas for rigging the PXW-FX9. In the video I cover things like base plates including VCT and Euro Plate. I look at hand grip options, rod rails and matte boxes as well as power options including V-mount adapters and the XDAC-FX9. Of course everything in the video is based on my own personal needs and requirements but I think there is some good information in there for anyone looking to accessorize their FX9, whether for working from a tripod or handheld.
Sony have released the PXW-FX9 user guide that I wrote for them. The guide is in the form of a searchable PDF designed for reading on a mobile device. The idea being that you can keep it on your phone in case you need to reference it on a shoot. It’s not meant to replace the manual but to compliment it and answer questions such as – what is S-Cinetone?
To download the guide go to the main Sony PXW-FX9 landing page and scroll down towards the bottom. There you should find a link that will take you to the guide download page as well as other resources for the FX9.
I received this timely reminder from the guys at Pag Batteries and it contains important information even if you don’t have one of Pag’s excellent batteries. The main one being that you should not store lithium batteries full charged.
If you are currently unable to work as a result of the global pandemic, then you need to make sure that your Li-Ion camera batteries are in good health when it becomes possible to return to work.
Batteries naturally self-discharge over time. If their state-of-charge is less than 10% before an extended period of inactivity, they could become difficult for you to recover.
It is also undesirable for batteries to be 100% charged for storage as this can damage the cells and lead to a shorter overall life.
PAG recommends that you charge your Li-Ion batteries to 50% (anywhere between 20% and 80% is desirable) prior to long term storage of more than 2 weeks. PAGlink batteries should also be in an unlinked state during this period.
PAGlink Sleep Mode for Storage
PAGlink Batteries can be put into Sleep Mode for long term storage, using the battery display menu system. It shuts down the internal electronics and greatly reduces battery self-discharge. The battery can be woken-up with 2 presses of the display button.
Please refer to Section 6 of the User Guide for PAGlink Batteries via the links below:
With some difficult times ahead and the need for most of us to minimise contact with others there has never been a greater need for streaming and online video services that now.
I’m setting up some streaming gear in my home office so that I can do some presentations and online workshops over the coming weeks.
I am not an expert on this and although I did recently buy a hardware RTMP streaming encoder, like many of us I didn’t have a good setup for live feeds and streaming.
So like so many people I tried to buy a Blackmagic Design Atem, which is a low cost all in one switcher and streaming device. But guess what? They are out of stock everywhere with no word on when more will become available. So I have had to look at other options.
The good news is that there are many options. There is always your mobile phone, but I want to be able to feed several sources including camera feeds, the feed from my laptop and the video output from a video card.
OBS is s great piece of software that can convert almost any video source connected to a computer into a live stream that can be sent to most platforms including Facebook and YouTube etc. If the computer is powerful enough it can switch between different camera sources and audio sources. If you follow the tutorials on the OBS website it’s pretty quick and easy to get it up and running.
So how am I getting video into the laptop that’s running OBS? I already had a Blackmagic Mini Recorder which is an HDMI and SDI to thunderbolt input adapter and I shall be using this to feed the computer. There are many other options but the BM Mini Recorders are really cheap and most dealers stock them as well as Amazon. it’s HD only but for this I really don’t need 4K or UHD.
Taking things a step further I also have both an Atomos Sumo and an Atomos Shogun 7. Both of these monitor/recorders have the ability to act as a 4 channel vision switcher. The great thing about these compared to the Blackmagic Atem is that you can see all your sources on a single screen and you simply touch on the source that you wish to go live. A red box appears around that source and it’s output from the device.
So now I have the ability to stream a feed via OBS from the SDI or HDMI input on the Blackmagic Mini Recorder, fed from one of 4 sources switched by the Atomos Sumo or Shogun 7. A nice little micro studio setup. My sources will be my FS5 and FX9. I can use my Shogun as a video player. For workflow demos I will use another laptop or my main edit machine feeding the video output from DaVinci Resolve via a Blackmagic Mini Monitor which is similar to the mini recorder but the mini monitor is an output device with SDI and HDMI outputs. The final source will be the HDMI output of the edit computer so you can see the desktop.
Don’t forget audio. You can probably get away with very low quality video to get many messages across. But if the audio is hard to hear or difficult to understand then people won’t want to watch your stream. I’m going to be feeding a lavalier (tie clip) mic directly into the computer and OBS.
I think really my main reason for writing this was really to show that many of us probably already have most of the tools needed to put together a small streaming package. Perhaps you can offer this as a service to clients that need to now think about online training or meetings. I was lucky enough to have already had all the items listed in this article, the only extras I have had to but are an extra thunderbolt cable as I only had one. But even if you don’t have a Sumo or Shogun 7 you can still use OBS to switch between the camera on your laptop and any other external inputs. The OBS software is free and very powerful and this really is the keystone to making this all work.
I will be starting a number of online seminars and sessions in the coming weeks. I do have some tutorial videos that I need to finish editing first, but once that’s done expect to see lots of interesting online content from me. Do let me know what topics you would like to see covered and subject to a little bit of sponsorship I’ll see what I can do.
Stay well people. This will pass and then we can all get back on with life again.
As camera resolutions increase and the amount of detail and texture that we can record increases we need to be mindful more and more of temporal aliasing.
Temporal aliasing occurs when the differences between the frames in a video sequence create undesirable sequences of patterns that move from one frame to the next, often appearing to travel in the opposite direction to any camera movement. The classic example of this is the wagon wheels going backwards effect often seen in old cowboy movies. The cameras shutter captures the spokes of the wheels in a different position in each frame but the timing of the shutter relative to the position of the spokes means that the wheels appear to go backwards rather than forwards. This was almost impossible to prevent with film cameras that were stuck with a 180 degree shutter as there was no way to blur the motion of the spokes so that they were contiguous from one frame to the next. A 360 degree shutter would have prevented this problem in most cases. But it’s also reasonable to note that at 24fps a 360 degree shutter would have introduced an excessive amount of motion blur elsewhere.
Another form of temporal aliasing that often occurs is when you have rapidly moving grass, crops, reeds or fine branches. Let me try to explain:
You are shooting a field of wheat, the stalks are very small in the frame, almost too small to discern individually. As the stalks of wheat move left, perhaps blown by the wind, each stalk will be captured in each frame a little more to the left, perhaps by just a few pixels. But in the video they appear to be going the other way. This is because every stalk looks the same as all the others and in the following captured frame, the original stalk may have moved say 6 pixels to the left. But now there is also a different stalk just 2 pixels to the right of where the original was. Because both stalks look the same it appears that the stalk has moved right instead of left. As the wind speed and the movement of the stalks changes they may appear to move randomly left or right or a combination of both. The image looks very odd, often a jumbled mess, as perhaps the tops of the stalks appear to move one way while lower parts appear to go the other.
Notice in the pond 5 clip how it’s not only the railway sleepers that appear to move in the wrong direction or at the wrong speed but notice how the stones between the sleepers appear to look like some kind of boiling noise.
Like the old movie wagon wheels one thing that makes this worse is the use of too fast a shutter speed. The more you freeze the motion of the offending objects or textures in each frame the higher the risk of temporal aliasing with moving textures or patterns. Often a slower shutter speed will introduce enough motion blur that the motion looks normal again. You may need to experiment with different shutter speeds to find the sweet spot where the temporal aliasing goes away or is minimised. If shooting at 50fps or faster try a 360 degree 1/50th shutter as by the time you get to a 1/50th shutter motion is already starting to be as crisp as it needs to be for most types of shots unless you are intending to do some for of frame by frame motion analysis.
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