October 01, 2014, 07:14:56 AM

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Messages - DFM

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1
Technical Support / Re: Circular Polarising Filter
« on: September 29, 2014, 04:57:15 AM »
Plastics can change the polarization of light passing through them because they're very slightly birefringent (the refractive index is direction-dependent). The degree of birefringence relates to the internal stress in the polymer chains, so when you view a scene through a polymer sheet with one polarizer, the effect it has will be degraded. If you were to put another polarizer on the outside, you'd see rainbow colors. This will mess with the CP filter's ability to effect the outside scene cleanly.

In this case you're also fighting against reflections from different sources. The outside world is, in general, reflecting primary sunlight - so the reflections have an element of polarization that's perpendicular to the incident light (physics 101, the incident and reflected wavefronts interfere with one another based on the angle between them - Google for Brewster Angle). That's why a CP filter works best when your camera is at 90° to the sun. Inside the aircraft, any reflections from the inner surfaces will be from scattered light inside the cockpit, so the incident direction could be anything - and the polarization won't be the same. This is why you can't "tune out" both sides at the same time.


So you are suggesting the fact that the windows have some sort of polarisation in them they may react in reverse to the outside scenery.

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Technical Support / Re: Circular Polarising Filter
« on: September 28, 2014, 06:37:49 AM »
All plastics have some innate polarization, it's a byproduct of the internal stresses that form when they're molded (and why Perspex models of components were used for stress analysis before the days of CAD/CAM software). Even planar windows in fixed-wing cockpits are polarized, so a polarizer on your lens (LP or CP) will always introduce problems.

Realistically, the only way to get pro quality aerials is to remove the door, or mount the camera outside on a remote gimbal. With a wide angle lens and a cooperative pilot you *might* be able to get away with a fixed mount on the skid (I'm talking GoPro-style gear, not a 5D) - but they may not accept 'amateur' stuff clamped to the airframe. Without vibration isolation a DSLR can be shaken to bits.

From inside the canopy, you have to accept that you're shooting through a hideous optical surface (even a brand-new bubble is covered in bumps and scratches, they're only meant to keep the rain out). You can't prevent image softening and loss of contrast, but you can reduce the internal reflections in the same way you'd shoot in an aquarium - take a black cloth and hide underneath it, making yourself a lightproof tent against the inside of the canopy. Try to keep the lens a little way back from the inside surface so any imperfections in the line of sight are comparatively small, and avoid the smallest apertures so it's never in focus. If the sun's hitting your side it'll still create flares, nothing you can do to stop that. It's a good idea to wear gloves, so when you rest your fingers on the window to steady yourself you don't make fingerprints.

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Software & Accessories / Re: laptop for tethered shooting?
« on: July 24, 2014, 06:49:58 PM »
The controls do get small, though, everything is small, as Adobe does not seem to have put any effort into supporting High DPI displays yet.

Lightroom 5 fully supports HiDPI Retina displays, and on Windows it has a 200% UI font scaling option. Most of the CC products are in the same state. Windows rendering isn't as good as OS X Retina, because it has a number of issues with HiDPI scaling that Adobe are working closely with Microsoft to address. It will be a while before we get feature parity.

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Software & Accessories / Re: laptop for tethered shooting?
« on: July 21, 2014, 06:41:02 AM »
I also use a Surface Pro for remote location work - it's useful to have Lightroom and CC available to run quick edits for a client, and it's happy to run EOS Utility on the end of a 15m USB cable for polecam stuff. But there are some issues compared to a regular laptop:

- Relatively small, fixed SSD. Windows will take up half, so on a multi-day shoot with raw files or video, the entry-level models are easy to fill. The 256G versions are quite a hike in price. You can plug in external drives, but...
- Only one USB3 port. It's nice to have USB3 for a card reader, but if you're trying to copy from a card to an external drive or offload a card while tethered, you need a spiderweb of portable hubs, external battery packs; it starts looking messy.
- Battery life on the SP1 and SP2 aren't all that great; it is after all a laptop in a tablet case. I'm happy to get an hour of heavy-lifting before my SP2 complains. MS sell car chargers and the 'power cover' keyboard for another $200, but the options for an external battery pack are limited to say the least, thanks to the magnetic connector.
- You have a mini-displayport for plugging in a larger screen (up to 3840 x 2160); easy to find $5 adapters for HDMI or DVI, but the port itself is hardly what you call rugged, and short of superglue there's nothing on the Surface you can attach strain reliefs to.
- You cannot repair it, period. It's sealed, glued, welded, protected by a curse, then glued again. When the battery gets worn out, you have a placemat.

Having said that, you do get CPU performance comparable to laptops. I've converted and graded MLV raw footage on it to send dailies across; not exactly a 60-second job but it was a whole lot easier to hike to the location without a 17" XPS laptop ;)

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I've been using these things for years as macro lenses, either reversed or on a set of tubes (or both). They're renowned for image quality, which explains why the prices on eBay have shot up. The radioactive models are not as easy to identify as people think - most of them did have "TAKUMAR" on the front, but there's at least one batch of 50/1.4s that don't:

SMC PENTAX 1:1.4/50  ASHAI OPT. CO. JAPAN  = thorium
SMC PENTAX 1:1.4 50mm ASHAI OPT. CO. JAPAN = regular glass

If you're mounting on FF body and don't want to saw off the aperture lever (or you get one with creatures inside), it's not a difficult lens to strip apart. See http://retinarescue.com/pentax50mmf1.4.html

6
There are absolutely no plans to stop the perpetual licensing of Adobe's retail products (Lightroom and Elements). They will remain on sale as they are now, but the Lightroom Mobile features require a subscription version of the desktop product because the app stores don't allow the app itself to run under a subscription license. It's also the only legal way Adobe can add features to the product without selling you a new version.

As to the question that the Photography Plan price will change in future, yes of course it's possible that eventually the price may change to allow for inflation - in 20 years from now who knows what $9.99 will be worth - but the company have committed to keeping the price fixed, so nothing is going to happen for a long time. It's equally likely they would cut prices as the per-user operating costs reduce.


So I guess that means LR will not be continued as a standalone desktop software?

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EOS Bodies - For Video / Re: 25 or 24 f p/s?
« on: June 01, 2014, 03:39:34 PM »
The "what frame rate to use?" question gets as many arguments going as "is Canon better than Nikon?" - but unless you intend to broadcast your footage on a TV network or release a motion picture, there is no technical difference. Videos shot at 25/24/30/21.653781610 FPS will all play back just the same on a computer - indeed videos from iPhones use variable frame rates but nobody watching them would notice. Modern editing software can happily mix clips of different frame rates and render out something different at the end, if you want.

24 FPS is regularly claimed as "the frame rate movies use" but it's not true - the film stock may have moved at 24 FPS (chosen entirely to match the optical soundtrack) but the shutter in early movie projectors opens twice, so theater audiences were actually watching at 48 images per second. In Europe they used 25 FPS - no matter what anyone says, humans cannot see the difference between 25 and 24.

What you can see is the shutter angle - the ratio between the frame rate and the camera's shutter speed. If the shutter is only open for a small fraction of each frame, the images have no motion blur so the result is stuttery (Saving Private Ryan used that intentionally for effect, and early video cameras were notorious for it). The 'ideal' ratio is half, also known as "180 degrees" (literally half a circle, optical movie cameras had circular rotating shutters with a section cut away). If you shoot at 25 FPS, your shutter speed would be 1/50 sec. This creates enough motion blur to confuse the brain into seeing a continuous shot, without being too smeary. It's not a "rule", but it's a good place to begin (choosing 24 FPS you'd still use 1/50 as there's no 1/48 on a standard DSLR).

Because of this, you're stuck with the amount of light you can cram into the sensor for each frame - so one reason to use 24 instead of 30 FPS would be to eek out just a little more exposure in dark scenes; but the gain between 24 and 25 is barely noticeable. On the other hand, people often shoot at 30 FPS then play back at 24 to create a slow-motion effect - but only you know if that's something you need to do.

Shooting in very bright light with a wide aperture, you hit the problem of having too much light - film cameramen solve that with neutral density filters but if you don't have those, filming at 30 FPS will cut down the exposure on each frame and can be enough to solve that problem.

Aside from those questions, there's no particular reason not to use 24 on your camera, but it's not the most important factor in how your final result will look - the shutter angle and f/stop decide the "feel" of the movie, so don't get hung up on it.

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EOS-M / Re: Export from camera to USB flash drive
« on: May 13, 2014, 06:35:02 PM »
If you have a cellphone with USB OTG support, it can act as the host. You'd plug the phone, camera and the flash drive into a USB hub, and copy between the two drives using a file manager app on the phone. Note that most phones with OTG still need the peripherals to be powered.

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Software & Accessories / Re: Adobe Lightroom Mobile Version Official
« on: April 09, 2014, 10:17:41 AM »
Indeed it is, but in the iDevice world it's simpler to get into an app's sandbox via the Internet. Bouncing through iTunes or an ad-hoc LAN, iOS does like to 'optimize' files whether you want it to or not. This is an early stage of development, lots of things including 'local' sync methods are possible in future versions, it all depends on what users ask for. http://feedback.photoshop.com/photoshop_family is the place to make your suggestions and complaints, both equally welcome.

While I know you didn't design the product, sending all the data through the Adobe network is quite silly if you ask me.

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Software & Accessories / Re: Adobe Lightroom Mobile Version Official
« on: April 09, 2014, 06:51:51 AM »
There will always be arguments about whether the consumer products (Lr, Elements, etc) will go 'subscription only' in future, and Adobe can't do more than to say there are no plans. There really aren't, it's not something the target customers would accept. Maybe in 30 years when the entire concept of 'installing' something is dead and buried the idea will be forced upon us all, so Adobe cannot say "never".

Right now with LR Mobile version 1, all the data flows through Adobe's network, and there's a lot of it. I do understand people are angry about having to subscribe to get the app working (personally I didn't think it was a good idea), but it's not ad-funded and there are real costs to keep the thing operational. By all means complain about it, Adobe do take note of feedback. That's what people like me are here for - I don't mind being shouted at.

..and when I'm shooting on location I run Lr5 on a Surface Pro; quite frankly it's much better. I can shoot tethered, develop stuff and hand off the final results to a client while they're watching. I'd also suggest using a small laptop in the same way; the Surface is overpriced for what it is but I got the thing for testing, and forgot to give it back.. ;)

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Software & Accessories / Re: Adobe Lightroom Mobile Version Official
« on: April 08, 2014, 08:00:59 AM »
No, sorry. Lr Mobile is only available for customers with an active subscription (CC or the PS/Lr Photography Program). Perpetual licenses of Lightroom cannot sync with it.

Not available as standalone app  :(

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EOS Bodies - For Stills / Re: Canon EOS 7D Firmware 2.0.5 Now Available
« on: December 12, 2013, 03:24:09 AM »
Warning - The 2.0.5 firmware update is NOT compatible with Magic Lantern. It won't boot from a ML-enabled card at all. You can downgrade back to 2.0.3 easily enough, but if you're a ML user don't go near this patch.

13
Lenses / Re: Any Old Gem Macro Lenses?
« on: October 30, 2013, 10:12:49 AM »
Extension tubes only change the focus distance (shortening the minimum at the cost of preventing an infinity focus). Subjects can look bigger because you can get closer, but the perspective will suffer too. Teleconverters increase magnification and flatten perspective but don't significantly change the focus distance (there is a tiny change, maybe on a 400mm lens your MFD will increase by 20cm or so). Combining the two on a long telephoto you can get physically closer to your subject than the lens itself would usually permit, increasing the magnification without messing with the tele's perspective distortion (or lack thereof). You don't have to be crammed right up against the subject anymore, I tend to use a thinner extension tube so the lens will focus at a couple of feet at "infinity", so it should be giving the best image quality and I don't get shadows or scare the critters. Cranking a lens all the way to MFD is never a good idea.

Image quality won't be as good as with a dedicated macro, but an f/2.8 400mm macro lens is going to cost you a fair amount more. Although you lose a lot of light, for fieldwork all the bits do other things so there's less to hump up the side of a mountain.


So you're saying that using extension tubes will not only increase the focus distance, but the magnification/focal length as well? If that's true, then lets say I'm at 80mm on my lens. How many sized ones would i need to get to 150mm?

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Lenses / Re: Any Old Gem Macro Lenses?
« on: October 30, 2013, 08:04:20 AM »
If you're trying to get closer, macro extension rings are often the better option over bellows these days. The variability of bellows was important in the film days with primes, when getting the subject to fill the negative was all-important. A zoom lens and three extension rings will give you the same degree of adjustment, but in all but the super-cheap versions they'll also pass the electrical contacts through. Even when you're shooting manual it's handy to get the right EXIF data on file.

Going the other way, pairing teleconverters with a macro setup will increase the subject distance but you'll take a big hit on exposure. You can go to town and put TCs and extension tubes together on a 200mm telephoto, and you'll be snapping flies from 6ft away. Probably need a tripod for that though  ;)

15
There's a profile in the Downloader app for EF8-15 f/4L on either a 7D or 5D-II body.

Fisheyes and UWAs are a nightmare as everyone has a different view on what "correction" means. Do you want to completely-eliminate the barrel distortion and end up with a highly-cropped and stretched image, or just fix the vignette and CA?

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