HPX250: Does lowlight conditions cause softness in the picture?

M

mmaller

Well-known member
Just finished a shoot. I was recording at AVC-intra100-720 30p. I was using the 720p setting due to the duration of the event and I did not
have the time to offload the card.
The conditions of the shoot entailed existing light only so I was shooting at +6db of gain with the aperture at wide open most of the time.
I was also zoomed in to the maximum focal length of the lens.

I used an external HDMI 720p Monitor for focus reference because of the shooting conditions and to make sure I was in focus.
The Camera output looked good on the Monitor during shooting, and the focus looked sharp.
I had to struggle at times at maximum focal length with a wide open aperture to get critical focus, but I know that I hit the mark and was as focused as could be.

When viewing the material back at the studio on a 1080 monitor the footage looked a little soft.
When I viewed on the same monitor at 1:1 pixel mapping the footage looked a little better (obviously because it wasn't being scaled by the monitor)

But, I haven't experienced that big of a discrepancy from 720p footage being scaled to 1080p.
Now when I look at the footage even at it's native 720p dimensions it still looks a little soft.

Everyone talks about how sharp the HPX250 is, so I am a little concerned.

Is this the norm because the camera was wide open at maximum focal distance.
Is sharpness in the HPX250 compromised when using these settings?
 
I've had the 250 for about a year, so I've been able to get a good feel for how it performs in most situations. The scenario you describe is about as problematic as it gets. Low light with gain (PAP 1 may have helped...don't know if you used it.) Wide open aperture which will not give the best performance from the lens. Maximum focal length hurts too as does full wide, especially on that lens. 720 instead of 1080 kills ~20% of the resolution. (As for sharpness, sometimes even slightly soft images can look good on a LITTLE external monitor...I'm assuming your field monitor is much smaller than what you are viewing with in your studio.)

So, to answer your question, "Is this the norm because the camera was wide open at maximum focal distance. Is sharpness in the HPX250 compromised when using these settings?", my answer is absolutely yes. But, that goes for a lot of camera / lens combinations.
 
I was using the PAP 1 setting and the monitor I was using during the shoot was a 22inch model, which is considerably bigger than a field monitor.
In addition to the external monitor, I was using the focus in red on the camera, but the focal plane was so narrow that the focus in red really could not distinguish
the minute variations. Without the external monitor I would have been toast.
I thought I was good, and I was, as far as getting the focus correct, only to be disappointed by the outcome of the scenario - wide open/maximum focal plane.

I understand that it is not just the HPX250 that may have this issue, but I was disappointed never the less.
The more I use the camera/lens the more I realize it's shortcomings and how, just because you may have a long zoom ratio on your lens, it's not necessarily available
to you if want to achieve optimal results.
 
720 will be a bit softer, the chip is for 1080 so if you want the sharpest then shoot in 1080 and scale down in post. Low light does make matters more difficult I have also found. I shoot allot in 24, just to get the extra light. What I have found is if I color balance first even though its low light it looks much sharper (at least to me). I also change the focus in RED to B&W so I can make out the focus better, helps me. Everyday is a learning curve.
 
Would it have been better to purposely underexpose the image somewhat, setting the aperture closer to it's optimal 4.0 range and then pushing the exposure in post?
I was shooting in AVC-Intra 100 so theoretically the latitude should be there? Has anyone tried this to achieve more sharpness under these conditions?
 
mmaller said:
Would it have been better to purposely underexpose the image somewhat, setting the aperture closer to it's optimal 4.0 range and then pushing the exposure in post?

I was shooting in AVC-Intra 100 so theoretically the latitude should be there?

Has anyone tried this to achieve more sharpness under these conditions?
Click to expand...

If you were at maximum focal length, you were already shooting an effective f/3.2 due to the light loss at the end of the lens. Underexposing by stopping down would only serve to sharpen marginally but lose "information" and then add noise when you raise the level in post. Again, trade one thing for another.

To the best of my knowledge, you don't gain more latitude by shooting AVC-I 100 over say AVC-I 50 or DVCProHD.

Take any camera from any era and / or price and stress it to the max and beyond and it will give results less than in an ideal situation.
 
gkantziper said:
If you were at maximum focal length, you were already shooting an effective f/3.2 due to the light loss at the end of the lens. Underexposing by stopping down would only serve to sharpen marginally but lose "information" and then add noise when you raise the level in post. Again, trade one thing for another.

To the best of my knowledge, you don't gain more latitude by shooting AVC-I 100 over say AVC-I 50 or DVCProHD.

Take any camera from any era and / or price and stress it to the max and beyond and it will give results less than in an ideal situation.
Click to expand...

You will get more data at 100, I just shot in 720 100. I will try it out and see when I start editing.

8-bit – 256 different values; 10-bit — 1024 different values

Adding sharpness does exactly what it’s supposed to do: make the edges more defined. I’ve never been a fan of sharpening, it might make an image pop a little more, but it’s not the same as actually having a lot of resolution. You can’t make a 720p image look like a 1080p image by sharpening, even on the web.
 
I believe that AVC-Intra 50 is 420 color space and AVC-Intra 100 is 422 color space. Both AVC50 & 100 are 10bit. That was why I went with AVC-Intra-100/ 720p. I believe DVCProHD is 8bit 422 and is also not a full raster dimension.
Are you saying my sharpness would have been improved if I went with AVC-Intrta 50 at 1080? which is an anamorphic format(1440X1080) and is also 420 color space.
The image is still being scaled by the camera when shooting in AVC-Intra 50 because of the native pixel dimensions of AVC-Intra 50.
 
There was a good resolution test shoot on the HPX-250's stock KG lens in this forum. The optimal sharpness zoom range is 45-55 %. Anything on the extreme wide or tele is to be avoided at all costs for low-light. I strongly suspect that your shot didn't fall into that zoom range. I myself have shot quite a few shots right after sunset's magic hour and the result was disappointing. But when it's within that 50% zoom lens, it's improved. But don't expect for the HPX-250's KG lens to look like a Zeiss Master Prime in low light.

AVC-I 100 codec (let alone the new AVC-I Class 200) can't miraculously improve lackluster optics and smaller 1/3" MOS sensor, especially on natural low light situations. Unfortunately in the real world it is not possible always stay within the 45-55% zoom range.
 
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mmaller said:
That was why I went with AVC-Intra-100/ 720p...
Are you saying my sharpness would have been improved if I went with AVC-Intrta 50 at 1080?
Click to expand...
Well, 1440x1080 is still quite a bit more than 1280x720, if you're talking about a progressive format. The difference is going to be color resolution vs spatial resolution, and 1440x1080 is still going to look substantially sharper than 1280x720 (unless it's 1440x1080i, in which case all bets are off).
 
Further -- there is no quality gain ever to be had from AVCI-50. AVCI-50 is not about quality, it's about bitrate; cramming what they can get into a maximum 50mbps. Always use AVCI-100 whenever you can, it will always always result in better image quality than AVCI-50.
 
Thank you for responding Barry.
So....
If the situation is such that you would need to shoot a 3 hour continuous event.
You have 2 - 64gig P2 cards, don't have the ability to offload the first card.
It is available low light only, and you are going to be relying on the far end of the zoom ratio (close to or maximum focal distance)
as well as the wide end.

What format would give the best results (meaning, perceivable resolution- sharpness) with the HPX250?
I for one, would have liked more sharpness than what I had gotten.
 
That's a situation I'd rather not get in. I'd attempt to rectify the problems through workable real-world fixes, rather than hoping for settings to make the difference.

First -- why can't you offload the first card?

Second, if it's absolutely impossible to offload the first card, why not just rent a third card for the day? Shouldn't cost more than $50 and would make all stress disappear.

Third, if you have to use the lens totally wide open and totally zoomed in, it's going to be a little softer than if you were using it at less than extreme conditions; that's pretty much the case with any lens. So is there no prospect whatsoever of either adding some light or getting closer? If it's not possible, then it's not possible, but you have to understand the limitations of what you're asking for. If you want a super-pristine image in low light at max telephoto, that's probably 2/3" camera territory, rather than 1/3".

Fourth, check the P.A.P. setting. P.A.P. 1 makes the camera more sensitive by squashing more noise, but may also be making the image softer in the process through the noise-reduction. P.A.P. 2 will be sharper, although not as sensitive. Determine which is more important for your project.

Fifth, overall camera settings can have a huge effect on perceived sharpness. Try a little experiment -- put Scene File F1 to detail -7, v-detail -7, coring +7, and gamma cine-D. Put Scene File 2 to detail +7, v-detail +7, coring -7, and gamma B.Press. Swap the scene file dial between the two, the perceived sharpness difference is just shocking. Now, I'm not recommending that you go using detail +7 all the time! Just pointing out that the settings can make a big difference, and so you may want to explore raising the settings versus what you did last time, if that helps.
 
I'd seriously consider adjusting the shooting parameters to fit 1/3" sensor class of camera and not stressing out the HPX-250. Else, just regrets and disappointments in the footage that only get worse when desperately trying to enhance it in post. Which one is more costly? Do it right the first time during shooting or spend 3-10x more in post to fix it and it still doesn't look right? I'd be willing to bet doing it right the first time is far less costly than fixing it later.
 
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