Noise problem

[Jerome Marot]

I looked at your two video samples. It could be that the first one is grainy because it is underexposed.

There is a drawback to the A1 long zoom: aperture is not constant. In the telephoto setting, the aperture is smaller than in the wide angle setting. If you use manual mode and set the aperture wide open in wide angle, and then zoom in, the telephoto setting will be underexposed.

Furthermore, filming at see is tricky: you'll have plenty of light, but the see is relatively dark, so the water may be underexposed if reflections of the sun or bright objects are in the picture.

[Matthew Ebenezer]

Originally Posted by John Cambell

Hey guys, we had a little south swell yesterday so me and my friends went and surfed and tried out the new settings on the xh a1. It looks a lot better then my other footage I got. Heres a little movie I put together of our 2 sessions. If you have any more advice I would love to hear it. Thanks

http://vimeo.com/1139050

Hey John,

The footage in your new clip is definitely better quality than your first one.

My only thoughts would be that the foam/froth of the breaking waves is quite blown out - but you've done really well overall - a big improvement over your first clip.

What settings did you change?

[John Cambell]

Hi Matt, I also did realize that the whitewash looked a little white also. I pretty much changed all my settings. Last time I was shooting in Auto setting and this time I used Manual. I used 3db custom preset, shutter speed 1/60, auto focus, and image stabilization (which might have messed up a few shots), and I kept exposure at 5.6 because I heard you get best resolution at that setting. Gain was at -3 and I used outside white balance setting. 60i. I think thats pretty much it. Do you think if I shot in 30f it would look more like something that you see in a professional dvd?

[Richard Hunter]

Originally Posted by Phil Taylor

As Marshall stated, "Depth of field decreases as the F-stop number shrinks. Conversely, if there's more light to work with, you can go to a higher F-stop such as 5.6, 16 or 22. The higher the F-stop, the more depth of field there is and so the greater the range of focus."

Hi Phil. This is not good advice to give to anyone using a videocam that has a small sensor. Yes the depth of field is greater at small apertures but at the same time the image loses sharpness due to diffraction. You end up with a picture where nothing is sharp at all. Maybe Marshall had a specific class of camera in mind when he wrote that?

You say it looks good "and always will" but my own experience does not support that at all. A couple of comparison shots of some detailed stuff like plants and trees at wide and narrow apertures will show quite different sharpness levels.

Richard

[Richard Hunter]

I dug up this old article about diffraction.

http://www.dvinfo.net/canon/articles/article19.php

Although it talks about f8 and f16 here, you need to bear in mind that the camera mentioned has a lower resolution sensor compared with the XH-A1. When you talk about HDV resolution sensors, the diffraction effects start at an even larger aperture.

Richard

[Mark Fry]

Originally Posted by Phil Taylor

No typo here. I do shoot quite a bit of video at f11. It looks good and always will if you have enough light to use the smaller lens openings. Otherwise, Canon would not supply such a lens. Nope, I do stand by my statements and suggest John Campbell try a faster shutter speed at f11 (if there is enough light and outdoors in the sun there will be plenty of light). If you want a large depth of field, a desire for most outdoor videographers, you'll have to use larger numbers for iris openings. As Marshall stated, "Depth of field decreases as the F-stop number shrinks. Conversely, if there's more light to work with, you can go to a higher F-stop such as 5.6, 16 or 22. The higher the F-stop, the more depth of field there is and so the greater the range of focus."

I'm afraid that Phil's advice is not good, at least as far as video cameras like the XH-A1 are concerned. The essential point to keep in mind is that the CCDs, at only 1/3", are very small, compared with film and even digital-SLR photography. This means that the focal-length of the lens is very short (something like 4.5mm at the wide end, IIRC, which gives a similar angle of view to the 35mm lens on a 35mm camera) and therefore, diffraction effects from very small appertures (less than 1mm at f8??) start to be a significant problem. I don't expect anyone to take my word for it. Adam Wilt's recent review of the Sony Z7 includes a short discussion and a perfect illustration of the effect (see this thread).

Likewise, except at the long end of the zoom, or when focusing on close objects, depth-of-field is not a problem with such small detectors. Of course, HD is less forgiving of poor focus that SD, but with a little care and knowing when you can and cannot trust the auto-focus, you shouldn't have a problem getting sharp images at f4 - f5.6 with these cameras.

As for using fast shutter speeds - do the experiment and decide for yourself whether the stuttery motion effect is what you want. Personally, I'd add ND filters and keep the smooth motion, rather than speed-up the shutter.

At least the XH-A1 gives us the facilities to adjust these parameters ourselves to create the effects we want. The difficult part is understanding what happened when we get effects we didn't intend!

[Phil Taylor]

Ooohhhhhhhhhhhhh. Well I guess I should stand corrected. However, there is more to this subject than meets the eye in this forum. I will attempt to respond to the diffraction issue later (the technical details are a struggle for me) however I stand by my statement abut shoting at f11. The Canon literature states "You can select from 21 aperture settings (with HD 20? L IS lens). The setting can be adjusted in 1/4 steps. However, only the following numbers are displayed on the screen: F1.6, F2.0, F2.8, F4.0, F5.6, F8.0, F9.5, CLOSE." Now, though you may see 9.5 in the viewfinder what that means to me is really an f stop of f11, the maximum of this lens. The 1/4 step situation is a bit confusing but I believe that when you see 9.5 in the viewfinder, depending on the light intensity, you are actually at f11. Then chromatic abberation and/or diffraction can occur depending on a number of other factors. It is most commonly seen on the edges of buildings or stand out subjects and may represent itself in overall softness of the image. I don't see that in my outdoor video. And there is a reason for that also. But one just has to shoot and observe what the video looks like to see if you are experiencing diffraction. The laws of physics as they relate to diffraction seem clear and locked in stone except for the occasional variances permited by lens design changes, Flourite lens elements for example.