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Old February 4th, 2011, 08:01 AM   #46
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Well every AF100 I have seen up on a res chart is more like 800 lines. And no I am not in a position to tell you proprietary engineering information. I just know that it does not pixel bin, nor line skip.

Thanks,

Jan
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Old February 4th, 2011, 10:48 AM   #47
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Hi Jan, here are some extracts from a chart. I realise lens choice has an effect, but information I have suggests that the results shown in these chart extracts are being replicated. I would be interested as to why, for example, the chart shows some very strange issues, such as why there is still aliasing showing even when there is no apparent detail shown (eg in the circular section of the chart I have attached)?

This cannot be put down to a lens or focus issue because for aliasing to occur, there has to be detail in the first place.
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Old February 4th, 2011, 11:23 AM   #48
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How were these stills produced? They are very small, 227x354, not HD resolution, therefore unreliable examples of the problem. Could you post 1920x1080 stills of the charts?
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Old February 4th, 2011, 11:57 AM   #49
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They are 100% crops of a res chart. Totally reliable I assure you. Though they had to be recompressed for the web, the detail on show is the same as the original. As I mentioned, others are finding similar results.

I didn't post the whole chart because it isn't necessary. The crops I have posted are the focal points of the issues I mention.
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Old February 4th, 2011, 12:52 PM   #50
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Quote:
Originally Posted by Jan Crittenden Livingston View Post
Well every AF100 I have seen up on a res chart is more like 800 lines.
Jan, the problem with standard resolution charts (with just horizontal and vertical lines) is that it's extremely difficult to tell the difference between real detail and aliasing. I assume those are the res charts you've seen? You know the input to the system is 800lp, you can see an output for that block, you therefore think "oh, it's resolving 800lp". This is the case with the second image Simon Wyndham has just posted.

Use a zone plate (or, like Simon Wyndhams examples, at least a circular resolution chart) and it all becomes vastly clearer. True (or "real") detail resolves as it should according to the original chart, aliasing shows as a false,arc whose centre appears to be somewhere other than the centre of the pattern. Simon Wyndhams first image shows the aliasing well. On the fourth ring (the 800lph ring), the circles appear to have a centre to the left of the chart - they are clearly aliases.

Use a true zone plate (rather than a circular resolution chart with bands) and it becomes far easier to do measurements - all Simons chart tells you is that it can resolve 600lp, but it can't resolve 800lp. As I said in the previous post, it seems to be very close to 625 line pairs (Simons previous estimate of "650-700 TVL of good resolution" is actually over optimistic!). If I could measure it accurately enough, I'd put a very, very large bet that I'd find it to be actually 622 lp, as that correlates with exactly one quarter of the sensor pixel count.
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Originally Posted by William Hohauser
How were these stills produced? They are very small, 227x354, not HD resolution, therefore unreliable examples of the problem.
If they are 1:1 pixel crops, (rather than downscales) they are fine. They agree in essence with similar examples I've seen, and other people have as well.
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Old February 4th, 2011, 01:07 PM   #51
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Things to bear in mind.

Lens matters tremendously, you also have to be really sure of the focus. Not always easy. Slightly OOF and result is meaningless. Sharpening can cause problems and viewing on a computer screen can cause moire.

I will run some checks with charts next week using different lenses, and I guarantee I can get different results. I will post my findings here.

I will also compare HDSDI out direct recorded to NF and to AF100 native CF card.

You also have to try different scene settings to be fair.
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Old February 4th, 2011, 01:26 PM   #52
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Quote:
Originally Posted by Olof Ekbergh
Things to bear in mind.

Lens matters tremendously, you also have to be really sure of the focus. Not always easy. Slightly OOF and result is meaningless.
Not true. In the case of a too soft lens, or being out of focus, all that happens is the amount of aliasing drops off, as does the mtf of the coarser (true) detail.

What doesn't change is the aliasing pattern in terms of fundamental shape, and where the aliases appear to be focussed. (The centre of the circle of which the arc is a part.) That's fundamental to the sensor pattern, and how the image is derived.

I believe this is exactly what Simon meant by "This cannot be put down to a lens or focus issue because for aliasing to occur, there has to be detail in the first place."

I don't see how scene settings are likely to affect max resolution.....?
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Old February 4th, 2011, 01:36 PM   #53
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Quote:
Originally Posted by Simon Wyndham View Post
Hi Jan, here are some extracts from a chart. I realise lens choice has an effect, but information I have suggests that the results shown in these chart extracts are being replicated. I would be interested as to why, for example, the chart shows some very strange issues, such as why there is still aliasing showing even when there is no apparent detail shown (eg in the circular section of the chart I have attached)?

This cannot be put down to a lens or focus issue because for aliasing to occur, there has to be detail in the first place.
So did you shoot this, and what chart was used?
Or is this someone else's test?
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Old February 4th, 2011, 04:24 PM   #54
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Quote:
Originally Posted by Simon Wyndham View Post
They are 100% crops of a res chart. Totally reliable I assure you. Though they had to be recompressed for the web, the detail on show is the same as the original. As I mentioned, others are finding similar results.

I didn't post the whole chart because it isn't necessary. The crops I have posted are the focal points of the issues I mention.
Thank you for clarifying that.

These images are in focus otherwise the aliasing pattern would not be there. It doesn't seem to be a lens issue. How do the detail adjustments affect this aliasing issue? Is the low pass filter adjustable?
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Old February 5th, 2011, 03:32 PM   #55
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Simon Wyndham: tests demonstrate "camera is only really producing 650-700 TVL of good resolution, rather than 900-1000 odd TVL that one would expect from a true 1080p camera,"

Jan then replied that she sees Res charts with more than 800 lines.

I'm sure Jan is being forthright. Are there circumstances where these different results could occur?

My main question: for a point of reference, what would a 1080p camera in the same price range -- the EX1R for example -- have for lines?
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Old February 5th, 2011, 03:59 PM   #56
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If I remember correctly (I have an EX3), about 1000.
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Old February 5th, 2011, 04:04 PM   #57
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Yep, the EX series is just shy of 1000, and with minimal aliasing.
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Old February 5th, 2011, 04:16 PM   #58
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Quote:
Originally Posted by James Campbell
Jan then replied that she sees Res charts with more than 800 lines.

I'm sure Jan is being forthright. Are there circumstances where these different results could occur?
The apparent contradiction is easily explained. Look at Simon Wyndhams second photograph - the one with the resolution blocks of horizontal lines. You can clearly see lines seemingly "resolved" on the 800 line resolution block. I'm sure this is what Jan is seeing.

Trouble is - it's aliasing. It's "false" - apparent - resolution.

That's obvious from Simons other photograph and the circular rings, especially the ring corresponding to 800. When near horizontal, the lines are bent the opposite way to the lower rings for resolution - their apparent centre is not the centre of the chart. They are aliases. They don't truly represent the pattern on the chart.

There is also another way to think about it. Look again at Simons second photograph. ( af101-horizontal.jpg ) In the blocks 200, to 400, to 600, the lines get closer together - as they should, same as the real chart. But look closely at the "800" block. The lines appear to not be as close together as in the previous (600) block. Why? Because they are aliases.

You can just still see "detail" in the 1000 block - but the lines are then even further spaced apart. Exactly what would be expected from aliases.

For this camera, it can resolve 600 TVL - it can't resolve 800. It appears to - but is just aliasing.
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Old February 8th, 2011, 05:27 AM   #59
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Stupid question (as I'm deciding between the EX1R and the AF100): for approximately the same price, I could buy an AF100 along with a NanoFlash unit as compared to an EX1R. Wouldn't using the NanoFlash with the AF100 and being able to record at such a high bitrate with 4:2:2 color raise the quality of the AF100 video capture above what the EX1R captures natively? (I know it's a newbie question... I'm just not sure what happens when in the capture process to capture higher resolution).
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Old February 8th, 2011, 11:05 AM   #60
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The Nanoflash can only record what the camera gives it. So if the AF-100 captures 700 or 800 lines then the Nanoflash will record 700 or 800 lines.

What the Nanoflash does for you is record those 700 or 800 lines with more information which leads to a closer representation to the uncompressed signal.
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