Tag Archives: dslr

How big a compromise is using a DSLR zoom on a 4K camera?

This came up as a question in response to the post about my prototype lens adapter. The adapter is based around an electronic Canon EF mount and the question was, what do I think about DSLR zooms?

There is a lot of variation between lenses when it comes to sharpness, contrast and distortions. A zoom will always be a compromise compared to a prime lens. DSLR lenses are designed to work with 24MP sensors. A 4K camera only has around 9MP, so your working well within the design limits of the lens even at 4K. While a dedicated PL mount zoom like an Angenieux Optimo will most likely out perform a similar DSLR zoom. The difference at like for like apertures will not be huge when using smaller zoom ratios (say 4x). But 10x and 14x zooms make more compromises in image quality, perhaps a bit of corner softness or more CA and these imperfections will be better or worse at different focal lengths and apertures. At the end of the day zooms are compromises but for many shoots it may simply be that it is only by accepting some small compromises that you will get the shots you want. Take my storm chasing shoots. I could use primes and get better image quality, but when you only have 90 seconds to get a shot there simply isn’t time to swap lenses, so if you end up with a wide on the camera when a long lens is what is really needed, your just not going to get the shot. Using a zoom means I will get the shot. It might not be the very best quality possible but it will look good. It is going to be better than I could get with an HD camera and a very slightly compromised shot is better than no shot at all.
If the budget would allow I would have a couple of cameras with different prime lenses ready to go. Or I would use a big, heavy and expensive PL zoom and have an assistant or team tasked solely with getting the tripod set up and ready asap. But my budget isn’t that big. I could spend weeks out storm chasing before I get a decent shot, so anything I can do to minimise costs is important.
It’s all about checks and balances. It is a compromise, but a necessary one. It’s not a huge compromise as I suspect the end viewer is not going to look at the shot and say “why is that so soft” unless they have a side by side, like for like shot to compare. DSLR zooms are not that bad! So yes, using a DSLR zoom is not going to deliver quality to match that of a similar dedicated PL zoom in most cases, but the difference is likely to be so small that the end viewer will never notice and thats a compromise I’m prepared to accept in order to get a portable camera that shoots 4K with a 14x zoom lens.

What about DSLR primes and why have I chosen the Canon Mount?

This is where the image performance gap gets even narrower. A high quality DSLR prime can perform just as well as many much more expensive PL mount lenses. The difference here is more about the usability of the lens. Some DSLR lenses can be tiny and this makes them fiddly to use. They are all All sorts of sizes, so swapping lenses may mean swapping Matte boxes or follow focus positions etc. Talking of focus, very often the focus travel on a DSLR lens is very, very short so focussing is fiddly. If the lens has an aperture ring it will probably have click stops making smooth aperture changes mid shot difficult. My prime lenses are de-clicked or never had clicks in the first place (like the Samyang Cine Primes). It’s not so much the issue of requiring a finer step than the one stop click, but more the ability to pull aperture during the shot. It’s not something I need to do often, but if I suddenly find I need to do it, I want a smooth aperture change. That being said, one of the issues with using Canon EF lenses with their electronic iris is that they operate in 1/8th stop steps and this is visible in any footage. Ultimately I am still committed to using the Canon mount lenses simply because there are so many to choose from and they focus in the right direction unlike Nikon lenses which focus back to front. For primes I’m using the excellent and fully manual Samyang T1.5 Cine Primes. I really like these lenses and they produce beautiful images at a fraction of the price of a PL mount lens. My zoom selection is a bit of a mish-mash. One thing about having a Canon mount on the camera is that I can still use Nikon lenses if I fit the lens with a low cost Nikon to Canon adapter ring. If you do this you can only use lenses with an actual iris ring, so generally these are slightly older lenses, but for example I have a nice Sigma 24-70mm f2.8 with a manual iris ring (and it focusses the RIGHT way, like most Sigmas but unlike most Nikon mount lenses). In addition I have a 70-300mm f4 Nikon mount Sigma as well as an Old Tokina 28-70mm f2.6 (lovely lens, a little soft but very nice warm colour). One thing I have found is that most of the Nikon to Canon adapter rings are little bit on the thin side. This prevents any zooms from being Parfocal as it puts the back focus out. Most of the adpaters are made in two parts and it’s quite easy to take the front and back parts apart and add shims made out of of thin plastic sheet or even card between the two halves to correct the back focus distance.

So there you have it. Overall DSLR lenses are not a huge compromise. Of course I would love to own a flight case full of good quality PL mount, 4K ready, glass. Perhaps one day I will, but it’s a serious investment. Currently I use DSLR lenses for my own projects and then hire in better glass where the budget will allow. For any commercials or features this normally means renting in a set of Ultra Primes or similar.  I am keeping a close eye on the developments from Zunow. I like their 16-28mm f2.8 and the prototype PL primes I saw at NAB look very good. I also like the look of the Zeiss 15.5 to 45 light weight zoom. Then of course there is the excellent Fujinon 19-90mm Cabrio servo zoom, but these are all big bucks. Hopefully I’ll get some nice big projects to work on this year that will allow me to invest in some top end lenses.

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Using DSLR lenses on 3D rigs.

Just a quick note on a rather obscure subject. I do a lot of 3D work. Buying pairs of PL mount lenses for my F3’s is beyond my budget right now, so I hire in lenses when I need them. However for my own projects I use DSLR lenses, mainly Nikkors and Tokina’s. One thing that i have discovered is that many of the older manual Nikkors have a tendency to shift the image left and right when you focus. This then miss-aligns the rig. The more modern internal focussing lenses are much, much better in this respect with little or no shift at all. The only problem with the more modern IF lenses is that they often don’t have iris rings (so iris is adjusted with a MTF adapter) and the focus control often has a slipping clutch making repeatable focussing a little harder. So neither is perfect. For 3D applications I think the more modern IF lenses are preferable.

Micro 4/3, Super 35, DSLR and the impact on traditional Pro Camcorders.

Micro 4/3, Super 35, DSLR and the impact on traditional Pro Camcorders.

I was asked by one of this blogs readers about my thoughts on this. It’s certainly a subject that I have spent a lot of time thinking about. Traditionally broadcast and television professionals have used large and bulky cameras that use 3 sensors arranged around a prism to capture the 3 primary colours. The 3 chip design gives excellent colour reproduction, full resolution images of the very highest quality. It’s not however without it’s problems. First its expensive matching 3 sensors and accurately placing them on a high precision prism made from very exotic glass. That prism also introduces image artefacts that have to be dealt with by careful electronic processing. The lenses that have to work with these thick prisms also require very careful design.
Single sensor colour cameras are not something new. I had a couple of old tube cameras that produced colour pictures from a single tube. Until recently, single chip designs were always regarded as inferior to multi-chip designs. However the rise of digital stills photography forced manufacturers to really improve the technologies used to generate a colour image from a single sensor. Sony’s F35 camera used to shoot movies and high end productions is a single chip design with a special RGB pixel matrix. The most common method used is by a single sensor is a bayer mask which places a colour filter array in front of the individual pixels on the sensor. Bayer sensors now rival 3 chip designs in most respects. There is still some leakage of colours between adjacent pixels and the colour separation is not as precise as with a prism, but in most applications these issues are extremely hard to spot and the stills pictures coming from DSLR’s speak for themselves.
A couple of years ago Canon really shook things up by adding video capabilities to some of their DSLR’s. Even now (at the time of writing at least) these are far from perfect as they are at the end of the day high resolution stills cameras so there are some serious compromises to the way video is done. But the Canons do show what can be done with a low cost single chip camera using interchangeable lenses. The shallow depth of field offered by the large near 35mm size sensors (video cams are normally 2/3?, 1/2? or smaller) can be very pleasing and the lack of a prism makes it easier to use a wide range of lenses. So far I have not seen a DSLR or other stills camera with video that I would swap for a current pro 3 chip camera, but I can see the appeal and the possible benefits. Indeed I have used a Canon DSLR on a couple of shoots as a B camera to get very shallow DoF footage.
Sony’s new NEX-VG10 consumer camcorder was launched a couple of weeks ago. It has the shape and ergonomics of a camcorder but with the sensor and lenses of a 4/3? stills camera. I liked it a lot, but there is no zoom rocker and for day to day pro use it’s not what I’m looking for. Panasonic and Sony both have professional large sensor cameras in the pipelines and it’s these that could really shake things up.
While shallow DoF is often desirable in narrative work, for TV news and fast action its not so desirable. When you are shooting the unexpected or something thats moving about a lot you need to have some leeway in focus. So for many applications a big sensor is not suitable. I dread to think what TV news would look like if it was all shot with DSLR’s!
Having said that a good video camera using a big sensor would be a nice piece of kit to have for those projects where controlling the DoF is beneficial.
What I am hoping is that someone will be clever enough to bring out a camera with a 35mm (or thereabouts) sized sensor that has enough resolution to allow it to be used with DSLR (or 4/3) stills camera lenses but also be windowed down and provided with an adapter to take 2/3? broadcast lenses without adding a focal length increase. This means that the sensor needs to be around 8 to 10 Mega Pixels so that when windowed down use just the center 2/3? and it still has around 3 million active pixels to give 1920×1080 resolution (you need more pixels than resolution with a bayer mask). This creates a problem though when you use the full sensor as the readout of the sensor will have to be very clever to avoid the aliasing issues that plague the current DSLR’s as you will have too much resolution when you use the full sensor. Maybe it will come with lens adapters that will have to incorporate optical low pass filters to give the correct response for each type of lens.
A camera like this would, if designed right dramatically change the industry. It would have a considerable impact on the sales of traditional pro video cameras as one camera could be used for everything from movie production to TV news. By using a single sensor (possibly a DSLR sensor) the cost of the camera should be lower than a 3 chip design. If it has a 10 MP sensor then it could also be made 3D capable through the use of a 3D lens like the 4/3? ones announced by Panasonic. These are exciting time we live in. I think the revolution is just around the corner. Having said all of this, I think it’s also fair to point out while you and I are clearly interested in the cutting edge (or bleeding edge) there are an awful lot of producers and production companies that are not, preferring traditional, tried and tested methods. It takes them years to change and adapt, just look at how long tape is hanging on! So the days of the full size 2/3? camera are not over yet, but those of us that like to ride the latest technology wave have great things to look forward to.

Canon T2i, first impressions, initial tests (frame grabs and video supplied).

t2i-EX Canon T2i, first impressions, initial tests (frame grabs and video supplied).
EX1 on left, T2i on right

As you may have seen from my earlier post I became the owner of the new Canon T2i (or 550D as it’s known in the UK) at the weekend. Clearly before using any camera in anger it’s important to see what it can and can’t do. I will say that I am not a Canon DSLR expert. I have been following the fuss and much admire some of the work done with these cameras by Phil Bloom, but frankly after playing with the Canon over the weekend I have to say I’m disappointed. Yes you can achieve shallow depth of field very easily and you do get a filmic look to the pictures, but look at the footage on a big monitor and it just looks soft. At first I wondered if this was the lens I was using, so I tried a couple of others including a nice Tamron 28mm prime. I tried different apertures, shutter speeds etc, but every clip I’ve taken looks soft. In isolation, on scenes with low detail this isn’t immediately apparent, but anything with lots of fine detail looks soft. Some of this is aliasing, look at the roof of the house in the T2i image, it appears to have diagonal roof tiles, this is a pretty typical aliasing artifact. I shot some closer shots of the buildings and the brickwork aliased like crazy.

t2i-flowers Canon T2i, first impressions, initial tests (frame grabs and video supplied).
EX1 on right, T2i on left

Looking at the flowers picture you can see that the EX1 has picked up more of the subtle texture, or at least it has recorded more of the texture. I’m sure some of the Canon’s softness is due to compression artifacts. The other thing that I found is that it is tending to crush blacks a bit. I have played around with the picture styles and you can reduce this a bit, but there is very little detail in deep blacks, which would IMHO make grading tricky. The one good thing I did find was that it is very noise free at 200 and 400 asa, it’s also useable up to 800 asa or at a push 1600asa, so it would make a good camera for very low key scenes, provided you use a good fast lens. Looking at the Canon pictures there was something pleasing about the deep, almost crushed blacks. I think this helps contribute to the Canon DSLR “look” so I quickly threw together a new picture profile for the EX1/3 and PMW-350, but I’m afraid that the details of that will be the subject of another post, as I have work that I must do first! The EX images in the frame grabs were shot with this picture profile. As we all know the ergonomics of the video DSLR’s is pretty poor for video. It’s tricky to hold and you have to use an add on Loupe to make the LCD useable as a viewfinder. You can’t zoom mid shot and without peaking or zebras adjusting exposure and focus accurately is difficult. I was hoping to be able to use the 550D as a B camera for those situations where I need a small, discreet camera, but having seen the pictures, so far, for me it will be reserved for holidays and shooting where you not supposed to video and for shoots where supper shallow DoF is essential. I have to say I’m really disappointed, I wanted this camera to be so much better, I knew it would suffer from aliasing, but I wasn’t expecting the soft pictures, I guess some will say that the softness adds to the filmic look, but I’d much rather do that with some nice pro-mists or filtration in post production rather than starting out with soft pictures. Perhaps I’ve done something wrong? If I have please add a comment!

UPDATE: I was so convinced that I must be doing something wrong that I shot some more clips, this time with less harsh lighting. No, change however, the T2i is still soft and the new clips show just how big a problem aliasing is. You have to consider that the coloured moire patterns are recorded like that, no amount of grading will get rid of it. A small amount of diffusion on the camera should help, but then your going to have to work out how much to soften and diffuse each shot to make sure your not making the pictures even softer than they already are.

t2i-aliasing Canon T2i, first impressions, initial tests (frame grabs and video supplied).
EX top, Canon T2i bottom

The frame grabs are all 1:1 pixel for pixel, no trickery has been used! You can download some further examples by clicking here. Even if you were shooting stuff for the web this level of aliasing could cause big problems as it’s really obvious. For this shot I had the Canons sharpness setting turned all the way down. I have also turned down the contrast setting as this gives better dynamic range with less crushed blacks. My workflow is to import the H264 files from the camera and then convert them to ProResHQ. This helps a little with sharpness over working with the native H264, but for me this last test was the nail in the coffin for DSLR’s as footage like this would simply be unusable. If you watch the YouTube clip please make sure you watch it full screen or at least at the 480P setting. The small embedded size doesn’t show the aliasing as much as the bigger versions.
FURTHER UPDATE:
OK, so it’s defiantly not just me doing something wrong. When in focus the T2i/550D aliases (as do all the current Canon DSLR’s). This is a grab from Philip Blooms latest Canon short. For once this is a daylight piece and as I expected it exhibits a lot of aliasing. The grab is actually taken from the thumbnail on his exposure room page. I’m really pleased to see this as it shows that aliasing is a problem for the experts too. You start to appreciate why so many of the Canon shorts are shot at night, with millimeter deep DoF… it’s to stay clear of having stuff in focus that will alias. there are filters from Caprock that are supposed to help, but you need a different filter for each focal length and aperture that you use, they also soften the picture somewhat.

PBaliasing Canon T2i, first impressions, initial tests (frame grabs and video supplied).
Aliasing in Phil Blooms latest edit

If you want my opinion, then it has to be that the Canon’s are close, but still a mile away. The aliasing issue is a biggie. Sort it out and the skew, jello and overheating can be worked around, but if you have to worry about simply having a piece of wood in focus and whether it’s going to exhibit rainbows of colour or whether cobble stones will twitter and change colour (At 00.35 and this is from Canon) then it will limit what you can do. There is quite a lot of aliasing in Phil’s new daytime clip, basically anytime anything is steady, has texture and is in focus, it aliases. I’ve been shot down in flames on other forums for saying that this is a problem, but if even the experts can’t deal with it then what hope does everyone else have? I would love to have the option of shooting with the shallow DoF that the Canon’s offer, but not at the expense of having to avoid any kind of texture. Perhaps Red and Scarlet will be better, perhaps Canon will sort it out, or perhaps not, as the cameras are clearly selling like hot cakes, even with the issues. If they do fix it then the camera will almost certainly be for video only.