2 questions: auto iris limit setting / audio vol level with included shotgun mic

[Tim Ducharme]

Hello,

I recently purchased the HVR-V1U camcorder. So far so good. There are just two questions that I hope someone can clarify:

1. What exactly does the "auto iris limit" setting really mean over the exposure? I have the HVR-V1U training video by Douglas Spotted Eagle from VAAST. Douglas recommends limiting the auto iris limit to f4. Why not f11, for example? When following the advice, for small sensor camcorders, to limit the iris to f4 is there any side-effect in some shooting situations?

2. As mentioned in another thread, the included Sony shotgun mic seems to record very low audio levels - it doesn't get close to reaching what would be considered peak signal strength. I have a Rode Videomic that performs well with the camcorder offering what one would expect in terms of signal strength. Is there a way to recod a stronger signal? I see that I can adjust the audio trim . . . but only in - db's. Why would Sony include a mic that can't offer sufficient levels?

Thanks. Any advice or info would be helpful.

[Bob Grant]

1. This is to avoid chromatic abberation from the small iris opening. The potential side effect is the camera then might have to increase shutter speed to control exposure and you might start to get fast action looking juddery even in interlaced. If that bothers you an additional ND filter would be called for.

2. What can I say. They didn't include a mic with the Z1, now they include a plastic thing with the V1. Rode make an inline preamp with 20dB gain that might cure your problem and it's a reasonable price:

http://www.rodemic.com/downloads/D-P...10305_prnt.pdf

This little amp probably should be in everyones kit but perhaps the money would be better spent on a better mic.

Edit: Just realised that Rode unit might have a problem with the Sony mic, the mic need phantom power and nothing in Rode's specs indicate if it passes the phantom power through to the mic. As they only talk about using it with dynamic mics my suspicion is it doesn't.

[Max Volki]

Originally Posted by Bob Grant

. Rode make an inline preamp with 20dB gain that might cure your problem and it's a reasonable price:

http://www.rodemic.com/downloads/D-P...10305_prnt.pdf

This little amp probably should be in everyones kit but perhaps the money would be better spent on a better mic.

Edit: Just realised that Rode unit might have a problem with the Sony mic, the mic need phantom power and nothing in Rode's specs indicate if it passes the phantom power through to the mic. As they only talk about using it with dynamic mics my suspicion is it doesn't.

Bob, read here:

Features
• Instrumentation grade pre-amplifier.
• balanced input and balanced output.
• Can be used with long cable runs with minimum losses.
• P48V phantom powered.


volki

[Piotr Wozniacki]

While the D-plug device seems nice, there's been sort of consensus here that the "beauty" (and the main reason to use at all) of the V1's stock mic is its small size and weght, so much desired when shooting hand-held. Adding a device like that denies this advantage; I believe its much better (and cheaper) to buy a more sensitive shotgun (can also be from Rode - the NT-G1 has a very good price/performance ratio).

[Piotr Wozniacki]

Originally Posted by Bob Grant

1. This is to avoid chromatic abberation from the small iris opening.

Bob, I'd say it's not so much CA that can be introduced by too small an aperture, but diffraction and related softness. BTW, you cannot limit it to anything else that F5.6 or F11; I sometimes wish there was a third value available in between.

[Stephan Stryhanyn]

Originally Posted by Piotr Wozniacki

BTW, you cannot limit it to anything else that F5.6 or F11; I sometimes wish there was a third value available in between.

With no user-specified limit (i.e. no iris limit), the default on the FX7E seems to be f6.2 before the camcorder increases shutter speed in AUTO mode - see discussion on ND4. So, is that so on the V1, too?

[Piotr Wozniacki]

Yeah, well - when you are in manual mode, and set a constant (manual) shutter speed but use auto exposure - withou a limit set in the menu, the aperture can close further than that!

[Bob Grant]

Originally Posted by Max Volki

Bob, read here:

Features
• Instrumentation grade pre-amplifier.
• balanced input and balanced output.
• Can be used with long cable runs with minimum losses.
• P48V phantom powered.


volki

Still does not tell me if the phantom power extends to the microphone. The amplifier is phantom powered i.e. it get phantom power from it's output. What the specs nowhere mention is if that phantom power carries through to the units input. I've emailed Rode to make certain but I suspect it doesn't.

[Bob Grant]

Originally Posted by Piotr Wozniacki

While the D-plug device seems nice, there's been sort of consensus here that the "beauty" (and the main reason to use at all) of the V1's stock mic is its small size and weght, so much desired when shooting hand-held. Adding a device like that denies this advantage; I believe its much better (and cheaper) to buy a more sensitive shotgun (can also be from Rode - the NT-G1 has a very good price/performance ratio).

Well if the D-plug will work I don't see how it denies anything, it's very small and pretty light. In fact Rode sell it without the case so one could with a little work fit the unit inside the XLR connector of the mic.

However yes if you must put a mic on the camera a better mic would be the go. The Rode shotguns are fairly long though. A Sanken CS-1 which is designed as an on camera mic would seem a better proposition. If you've got the money their CMS-10 gives you stereo and it's one very nice microphone.

The CMS-10 is around $2,200 but will outlast your next 5 cameras and still be worth what you paid for it. We bought ours 2nd hand at auction and paid over list price.

The advantage of the Sanken mics is they maintain their polar response down into the low frequencies so you don't get the reverb / roominess of convention shotguns when working small rooms. If you have to put a mic on a camera they are about the best there is.

[Bob Grant]

Just got an email from Rode, D-plug sadly does not pass phantom power to the mic, it's a no go with any mic that needs phantom power.

[Serena Steuart]

[QUOTE=Bob Grant;692621]1. This is to avoid chromatic abberation from the small iris opening. The potential side effect is the camera then might have to increase shutter speed to control exposure and you might start to get fast action looking juddery even in interlaced. If that bothers you an additional ND filter would be called for.

Stuff such as chromatic and spherical aberrations are reduced by closing the iris, which is the reason for the ancient rule-of-thumb "lenses perform best closed 1 stop from wide open". The reason for setting an f/4 limit (maximum closing) is diffraction limiting of resolution. Diffraction effects increase as the physical diameter of the aperture decreases. The lenses used on 1/4 inch CMOS sensors are necessarily of short focal length, so for a given f/number the hole the light is passing through is very much smaller than for, say, a 35mm camera. Given pixel dimensions and light wavelength you quickly come to the conclusion that resolution will be diffraction limited for apertures smaller than f/4 (ie higher f/numbers than f/4). Does it matter? It's something to know about and you really are throwing away resolution when closed to f/11.

[Steve Mullen]

Originally Posted by Serena Steuart

Stuff such as chromatic and spherical aberrations are reduced by closing the iris, which is the reason for the ancient rule-of-thumb "lenses perform best closed 1 stop from wide open". "It's something to know about and you really are throwing away resolution when closed to f/11.

Good post. Stay 1-stop from full open AND don't go smaller than f/5.6. Yes, you should not go lower than f/4, but that would leave you a very tiny exposure range considering you want to lock exposure.

Of course, you could lock the iris at f/3.6 -- and increase/decrease lighting to get the correct exposure.