Poor resolution on telephoto - is it normal? at DVinfo.net

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Sony XDCAM EX Pro Handhelds
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Old April 5th, 2009, 03:32 PM   #1
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Poor resolution on telephoto - is it normal?

The Fujinon lens of EX1 is a very sharp one, but with telephoto it loses.

I took a test series with the zoom on the 70, 80, 90 and 99 settings and with iris 4, 5.6, 8 and 11.

I converted the .bmp pics from Clip Browser to .gif and published the f5.6 pics on my own site.

Note the poor resolution on Z90 and Z99.

http://www.lentovision.se/bilder2/Z70f5,6.gif
http://www.lentovision.se/bilder2/Z80f5,6.gif
http://www.lentovision.se/bilder2/Z90f5,6.gif
http://www.lentovision.se/bilder2/Z99f5,6.gif

These results means that I have stopped using zoom90 and zoom99, reducing the max zoom to around 50 mm and the zoom range to around 10X.

My Canon A1 did not show this reduced resolution (at half the price tag).

Is this acceptable?

Should I send it to Sony for a replacement of the lens?
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Old April 5th, 2009, 03:50 PM   #2
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Hej!
I'm in the same position as you. I've just moved up from the XHA1 to EX1 and noticed the same issues with the lens. I sent it back to my dealer and we had a long telephone conversation and I've also talked to other people I know in the trade and I think it is basically that at the top end of the zoom you need to stop down to at least f8 to ensure no soft edges. I noticed that if you go to f11+ the image gets soft too, so the ND filter is my new best friend! Obviously if you still think there is a problem with your camera then send it back to Sony for a proper assesment. Anyone else out there have thoughts on this?....
Regards, Oliver.
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Old April 5th, 2009, 03:54 PM   #3
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Looks like chromatic aberration to me, you have red and green fringing causing the blurring. My EX3 does this too, but not as badly as yours I think, but I haven't shot charts.
F5.6 in on the edge of diffraction limiting your resolution too, F2.8 to F4 seem to be the sharpest.
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Old April 5th, 2009, 04:00 PM   #4
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Never shoot beyond f8 with that lens and I try to stay below that. There is serious bad chromatic aberration when you are at full telephoto shooting contrasty objects. That's what you get with a cheap HD camera - it is the nature of the EX
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Old April 6th, 2009, 01:16 AM   #5
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That's what you get with a cheap HD camera - it is the nature of the EX
Actually it's not that the camera is cheap. Generally classed as an excellent machine. You just need to pay $100K extra for an excellent zoom.
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Old April 6th, 2009, 01:35 AM   #6
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Actually it's not that the camera is cheap. Generally classed as an excellent machine. You just need to pay $100K extra for an excellent zoom.
Maybe so, but when Canon A1 - for half the price - could give me a decent resolution at max zoom - which is 20x - then I expected at least the same performance with EX1 at 14x.

Perhaps that was to expect too much. Most of you seems to advice me to accept the situation. And resolution in the rest of the zoom range is really good.

I need an EX3 to for wildlife ...
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Old April 6th, 2009, 02:20 AM   #7
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Don't get me wrong i love my Ex-1, but for HD of course its cheap and the trade off is the long end of that lens and the absurd inability to shoot at f8 & above.
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Old April 6th, 2009, 03:07 AM   #8
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I'm not sure that the physics is understood. Diffraction softening is related to the diameter of the aperture, which is related to focal length. If you don't like the fact that diffraction becomes an issue around f/4 then you are actually saying that you want a larger sensor. At least 2/3 inch and preferably like the RED. Of course if you put a 300mm lens on an EX3 then you certainly can use f/8 and higher (in terms of diffraction softening). I get good results at max focal length, so perhaps you should be looking at your back focus or other faults. I have seen a little CA on the edges with bright white objects (but I had to look for it), so make sure you are really checking real world usage. It certainly shows in your tests.

These comments are not "in support of a great camera", just to remind you that every camera has compromises and we have to be realistic in using what we've got. If you look at the cost of excellent HD zooms, then one can judge what ought to be expected in affordable gear. If you're shooting wildlife, then the lenses you'll be putting on your EX3 will each greatly exceed the price of the EX3 body.

EDIT: looking again at the posted gifs, I'm thinking that they really show that the MTF is lower at the long end of the lens.

Last edited by Serena Steuart; April 6th, 2009 at 07:50 AM.
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Old April 6th, 2009, 08:51 AM   #9
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I'm not techy or do well with viewing 'charts', but I know even at full zoom I get razor sharp images. But focus is obviously absolutely critical at full zoom, it's easier to miss than hit the sweet focus spot. If I'm shooting an animal or my kid at full zoom, at fairly close range, I can tell by the eyelashes when I nail the focus. It's friggin' amazing when nailed, but only so-so when not completely nailed (frustrating because I thought I nailed it in the field), and obviously horrible if I miss critical focus. Sometimes I don't know for sure until I get back and look at it on the big monitor, even though it looks great on the lcd. If possible (and it's not usually practical on a moving subject), I use the expanded focus at full zoom. All my 'tests' are strictly visual though, I'm not shooting charts, so take what I'm sayin' with a shot of Jose Cuervo.
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Old April 6th, 2009, 09:07 AM   #10
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Originally Posted by Sverker Hahn View Post
I took a test series with the zoom on the 70, 80, 90 and 99 settings and with iris 4, 5.6, 8 and 11.
It's been said here - but make your NDs your friend, and always use them well before the silent scream for them occurs in your v'finder.

Diffraction (read: loss of sharpness) starts to occur the moment you start to stop down the lens from maximum aperture. It's not generally apparent for a couple of stops because closing to f/2.8 or f/4 cleans up a lot of the fuzz caused by miss-centered elements and internal flare, but it's there of course.

If you shoot at f/5.6 and smaller apertures you will get softer and softer pictures. This has nothing to do with Sony or Fuji or price, it's all to do with the laws of optics and the way light travels and bends when it meets sharp edges (of which the diaphragm blades are a prime example).

tom.
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Old April 6th, 2009, 10:12 AM   #11
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It's been said here - but make your NDs your friend, and always use them well before the silent scream for them occurs in your v'finder.
I here that. I shot a festival in glaring daylight the other day and stopped down instead of engaging the ND filter. When I reviewed the footage back home on a bigger screen it looked almost Standard Def resolution.

Reshooting again in the same conditions today with ND1 and iris open, the sharpness was much better even zoomed right in. Learnt the hard way.
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Old April 6th, 2009, 10:25 AM   #12
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A lot of folk wonder how it is that smaller, domestic cams seem to get away without any apparent switchable NDs. The answer is of course that the smaller the chips, the earlier diffraction losses become apparent and the more ND is needed to void sharpness losses.

Cameras with 1"/5 chips (remember the PDX10?) generally won't let you stop down smaller than f/4.5, and cameras with 1"/6 chips often don't stop down at all once you zoom to telephoto. Although the 'display' readout will show you shot at f/8 (say) the camera will in fact be using max aperture and lots of internally applied ND filtration.

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Old April 6th, 2009, 11:06 AM   #13
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My problem is not a poor resolution at f8, but at the end of the zoom range. I donīt get better behaviour of the lens at f4.

Serena: what is MTF?

Why donīt a lot of people check the resolution of their lenses as soon as they get them? The smartest guys of this forum could create a manual, including test charts, so that each individual can see if the lens of their expensive (cheap?) EX1 is within what could be expected.

This Fujinon lens has been praised many times in this and other forums, so I did not think of poor tele resolution.

I regret that I didīt do this test long ago. I have got some poor footage because of max zoom, which I then thought was because the motif was out of focus ("how could I miss focus on this clip???").
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Old April 6th, 2009, 12:31 PM   #14
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I can't compare to your Canon,
But I have always felt that the very end of any zoom lens I've ever used was the worst part of the lens. I only just glanced at couple of your shots but it doesn't seem to me the Z99 @ 5.6 was that horrible. The CA was much more noticeable and you lose contrast (to be expected)but it doesn't look like the resolution fell apart terribly.

Maybe I'm too forgiving or didn't look at your charts enough.
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Old April 6th, 2009, 09:25 PM   #15
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MTF: Modulation Transfer Function. It measures the recorded variation of a signal compared to the input. Resolution is ability to distinguish between two adjacent points (so, as an aside, the pixel spacing of a sensor does not represent resolution, since you must record on at least two adjacent pixels to detect a difference between them). In photographic terms, as the spacing between black and white lines diminishes (i.e. the spatial frequency of the line pattern increases) there comes a frequency at which all is grey (the black is recorded as mid grey, as is the white). The modulation response is zero at that frequency and all above that. A good system will hold a high value of MTF and then roll off quickly. MTF in a poor lens will quickly diminish towards zero, although both lenses may achieve the same resolution limit. Google will provide several references, one of which is Modulation Transfer Function - what is it and why does it matter? - photo.net.

Do people check out their lens (and cameras) when they buy? Certainly. That is how I (and others) discovered vignetting in the early production models. And back focus problems. And ND filter problems. And why Sony replaced the lens on my camera.

In doing tests you need to record the conditions of the test; gamma, detail, etc. I've just had another look at mine full tele and although there is detectable CA near the edges this isn't enough to be seen on a real subject. Worst with detail off, really rather good with detail on.
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