Detailed info on HVR A1 Program AE modes?

[Gian Pablo Villamil]

Is there any place to find out exactly what the various Program AE modes on the A1/HC1 do?

I notice that there seem to be a few things that you can do via Program AE that are otherwise impossible.

[Michael Stowe]

Originally Posted by Gian Pablo Villamil

Is there any place to find out exactly what the various Program AE modes on the A1/HC1 do?

I notice that there seem to be a few things that you can do via Program AE that are otherwise impossible.

I don't think they are impossible to achieveat all, but the manual lists what each does. Most are just compensating for the sensors way of detecting exposure which is to take the entire area and average it out (atleast I believe this is how it is generally done). You don't always want this since your subject may be quite different from the overall picture. Shooting a person on a sunny day in the snow will make them very very dark. You could easily adjust the exposure manually to compensate for this which is something everyone should learn to do. Same thing with sunsets etc...

[Gian Pablo Villamil]

No, not quite. The manual lists what the AE modes are for, but not what they do in terms of exposure, shutter speed & focus.

Some of the Program AE modes lock focus to near or far objects, which can't be done manually.

[Michael Stowe]

Originally Posted by Gian Pablo Villamil

No, not quite. The manual lists what the AE modes are for, but not what they do in terms of exposure, shutter speed & focus.

Some of the Program AE modes lock focus to near or far objects, which can't be done manually.

I understand what you are saying, I guess I still prefer manual settings on both since the camera is pretty stupid when it comes down to it. It has no idea what you want it to focus on (whether you are shooting distant or not it will still go in and out of focus on auto settings), how you want things exposed (the famous amateur bright to dark to bright to dark as the camera makes its choices or that the world is not 18% gray :-) ) You can, to a point, lock focus to near or far objects though by using manual and knowing depth of field (although the A1 does not make this easy). Same with exposure using the histogram and zebra. As far as the manual...yep...it does not say exactly what is happening or how it limits what it focuses on to a certain distance. It would be interesting to know what is happening in the background like you asked though.

[Nick Outram]

A quick search of Google has drawn a blank but there must exist somewhere a matrix of exactly what each of the HC1 Program Modes does or allows to be set for things like exposure, Iris, focus, gain. At first I avoided these as assumed that the camera 'took over' but have since started using 'Portrait mode' a lot as you CAN use/set spot-exposure with it. We need info!

On another note the Iris (aperture) range is widely quoted as F1.8 to F2.1 for this camera -is this truely accurate or a manual missprint that has been widely circulated? If so this is a tiny range, hardly worth having and would seem to indicate the main way this camera exposes is by adjusting the shutter speed and electronic gain. Also, is it possible to state a '35mm equivalent' of this range in terms of DOF? (My guess would be something around F5.6 - F8)...

[Gian Pablo Villamil]

Originally Posted by Nick Outram

...If so this is a tiny range, hardly worth having and would seem to indicate the main way this camera exposes is by adjusting the shutter speed and electronic gain. Also, is it possible to state a '35mm equivalent' of this range in terms of DOF? (My guess would be something around F5.6 - F8)...

The camera also corrects exposure by dropping a couple of built-in ND filters into the optical path. I shot some footage of a solar eclipse recently, you can actually see the filter moving out of the way at totality.

[Graham Baker]

Originally Posted by Nick Outram

On another note the Iris (aperture) range is widely quoted as F1.8 to F2.1 for this camera -is this truely accurate or a manual missprint that has been widely circulated? If so this is a tiny range,

I *think* (but I could be wrong) that those apertures are not the full range of the iris but the max aperture at the extreme ends of the lens zoom range - F1.8 at max wide and F2.1 at max zoom?
If I am correct then this idicates the lens as being quite 'fast' as a lot of 10x zoom lenses have considerably less wide-open apertures at the max zoom end, around F4.0 for some, the HC3 is rated as F1.8 - F2.8, not quite as good as the HC1....

[Nick Outram]

Originally Posted by Graham Baker

I *think* (but I could be wrong) that those apertures are not the full range of the iris but the max aperture at the extreme ends of the lens zoom range - F1.8 at max wide and F2.1 at max zoom?
If I am correct then this idicates the lens as being quite 'fast' as a lot of 10x zoom lenses have considerably less wide-open apertures at the max zoom end, around F4.0 for some, the HC3 is rated as F1.8 - F2.8, not quite as good as the HC1....

Graham, I think you are right -that makes a lot of sense. I have since found this good article on technical details about what the HC1 is actually doing when it exposes. The table is excellant:

http://hdvforever.com/hdv/exposure/

-Open exposure will run everything from 0db gain and f8 in very bright conditions to 18db and f1.8 in dull condition. Note also how the sampler is intelligent enough to crunch the numbers down to 8 bits from the maximum possible range.

So back to the DOF issue -exposure 18 will be the start of Portrait mode (wide open aperture/Iris). I am guessing that within that row it will probably adjust the shutter speed so that if it goes over some maximum (1/10,000 sec?) it will start to apply gain...

In bright conditions, Portrait mode and a number of ND filters should keep the exposure wide and shutter speed low...

Comments?


Regards, Nick.

[Stu Holmes]

Originally Posted by Gian Pablo Villamil

Is there any place to find out exactly what the various Program AE modes on the A1/HC1 do?

I notice that there seem to be a few things that you can do via Program AE that are otherwise impossible.

LONG POST!

Gian

pls see below some testing i've done a little while back. Almost all of it is applicable to A1, and indeed quite a few Sony cams :

There are several PROGRAM AE modes in the A1, and other Sony cams.
These modes affect not only exposure etc in certain circumstances but also focus etc.I have a theory that these modes may be useful in certain circumstances, to solve / reduce one or two of the image issues that sometimes occur in the A1.
I don't actually have an A1, but do an Hc1000 and there is a lot of similarity between the two so what i thought i'd do is a bit of experimentation with the PROGRAM AE modes to try to pin down what they're doing. Below are the results.

I had certain expectations what would happen and i think of particular interest to some A1/hc1 owners will be the use of the SUNSET&MOON mode.
I shot at 3 consistent light levels, changing between modes, noting any obvious picture differences, and then reviewed on playback using the Data Code, and again visually noting any changes too.

PAL Camera on tripod, shooting in daytime in 3 different light-level scenarios:
SCENE 1) indoors, curtains partially closed, on tripod, shooting in 'Auto' mode comparing to the other Program AE modes. Camera suggested exposure in 'Auto' mode = 50th sec, f16, +18db gain. (i.e. MAX. exposure)

SCENE 2) indoors, curtains opened bit more, on tripod, shooting in 'Auto' mode comparing to the other Program AE modes. Camera's suggested exposure in 'Auto' mode = 50th sec, f16, +6db gain. (i.e. was FOUR clicks down from MAX.exposure)

SCENE 3) outdoors, on tripod, bright sunlight, polariser, scene included shadow areas, trees, cars, and a white wall etc. Camera's suggested exposure in 'Auto' mode = 50th sec, f3.4, +0db gain.


RESULTS IN SCENE 1:
straight AUTO exposure mode gave exposure of :
Exposure as per 'Data Code' = 1/50th sec, f1.6, +18dB.

SUNSET&MOON AE mode:
Exposure as per 'Data Code' = 1/50th, f1.6, +9db.
- this mode REDUCED gain by 3 stops. I expected this mode to reduce exposure and it did, but see the end for my conclusion.

PORTRAIT AE mode:
Exposure as per 'Data Code' = 1/50th, f1.6, +18db.
- NO reported exposure change BUT there was definitely increased shadow detail. unknown how it achieved this.

SPOTLIGHT AE mode: didn't test in this light-level

BEACH&SKI AE mode: didn't test in this light-level

-------
RESULTS IN SCENE 2 (a bit brighter than the 1st scene):
straight AUTO exposure mode gave exposure of :
Exposure as per 'Data Code' = 1/50th sec, f1.6, +9dB.

SUNSET&MOON AE mode:
Exposure as per 'Data Code' = 1/50th, f1.6, +9db.
- NO reported change in exposure, nor any viewable change. SEE LATER FOR MY CONCLUSION.

PORTRAIT AE mode:
Exposure as per 'Data Code' = 1/50th, f1.6, +9db.
- NO reported exposure change BUT, again, oddly, there was definitely increased shadow detail. How it achieved this is not known.

SPOTLIGHT AE mode:
Exposure as per 'Data Code' = 1/50th, f1.6, +9db.
- NO reported exposure change BUT it did seem to dim-down the brightest parts of the image, as i would expect from this mode. HOW it did it, i don't know, as there was no reported exposure change.

BEACH&SKI AE mode:
Exposure as per 'Data Code' = 1/50th, f1.6, +12db.
- it increased exposure by 3dB stop. I would expect it to increase exposure for this mode consistent with it's intended purpose.


-------
RESULTS IN SCENE 3 (Outoors, bright sunlight, varied scene, polariser used):
straight AUTO exposure mode gave exposure of :
Exposure as per 'Data Code' = 1/50th sec, f3.4, +0dB.

SUNSET&MOON AE mode:
Exposure as per 'Data Code' = 1/50th, f3.4, +0db.
- NO reported change in exposure, nor any viewable change. SEE LATER FOR MY CONCLUSION.

PORTRAIT AE mode:
Exposure as per 'Data Code' = 1/300th, f1.6, +0db.
- Went to maximum aperture, as i would expect, and took shutter to 1/300th to compensate. This is expected behavior. Again, it also did something to shadow areas, increasing detail.

SPOTLIGHT AE mode:
Exposure as per 'Data Code' = 1/50th, f3.4, +0db.
- NO reported exposure change BUT it did definitely dim-down the brightest parts of the image, suchg as a white wall in the sun and white cars too. This was confirmed with Zebra patterning.

BEACH&SKI AE mode:
Exposure as per 'Data Code' = 1/50th, f2.8, +0db.
- it increased exposure by half a stop. this is expected.

***************
CONCLUSIONS:

that's all very interesting you may say, but what use is this information ?

Well 3 very interesting practical conclusions of this testing (and some additional testing i did) are :

USEFUL CONCLUSION 1: The 'SUNSET & MOON' mode can be used as a 'Gain-limiting' mode. It will NOT affect the exposure at all EXCEPT when it gets really pretty dim and then it carries on like 'AUTO' mode UNTIL it gets to +9dB and it will not let the exposure increase beyond this. i.e. It is acting as a 'Restricted-gain mode'. This is confirmed by experimenting with other light levels.
For all the people who say "heck i can see all this grain in shadow areas in dim-light with the A1' then if this mode works in the same way, use this mode instead of AUTO in a dim situation, and you will restrict gain and therefore grain. In post-processing you can brighten the image, but you will crucially have not got nasty +18db gain whilst recording the shot.

USEFUL CONCLUSION 2: The 'PORTRAIT' mode's primary function of course is to bias the exposure towards maximum aperture and this it does. If you're outdoors on a sunny day and want to throw the background into a blur, then use a circ.polariser to act as a neutral-density filter and achieve max. aperture of f1.6 in this mode. What was less predictable is that Sony have programmed it to do soemthing interesting to shadow areas. They DEFINITELY appeared much more detail when in this mode. This may well help all the people who say "Heck there's a lack of shadow detail when i use the A1'.

USEFUL CONCLUSION 3: The 'SPOTLIGHT' mode's apparent function is too stop highlight areas bleaching out into a pure-white (would appear as such in Zebra-patterning). And this it certainly seemed to do, stopping highlights indoors and outdoors blowing out.
What is interesting here is that it visibly achieved this WITHOUT any indicated change in exposure. The Data code reported no change in exposure in all 3 scenes above, compared to 'AUTO'. But it was definitely apparent, confirmed via Zebra Patterning, that the highlights had been toned down. Again this seems to have been done via image processing.
This mode would be useful i believe to people who have struggled a little with highlights bleaching out on the A1. It doesn't appear to reduce exposure, but it definitely reigns in those areas in shot that tend to pure-white.

Thanks to anyone who has stayed with this post to the bitter end !
I must apply the caveat that this testing was done with an HC1000, not an A1, but it's apparent that the A1/HC1 works in a very similar way.

Certainly i think a very useful mode is the SUNSET&MOON mode can be used as a 'Gain-Limited to 9dB' mode, and footage then brightened in post.

Besides all the above which is related to exposure, there are differences in focussing between the modes. For eg. LANDSCAPE mode can be used to prevent cam from focussing on glass if you're filming thru a windshield etc.

[Gian Pablo Villamil]

Originally Posted by Stu Holmes

LONG POST!

Gian

pls see below some testing i've done a little while back. Almost all of it is applicable to A1, and indeed quite a few Sony cams :
...

Very useful, thanks! I will repeat your experiment with my A1.

I suspect that they are playing with gamma curves to maintain/enhance highlight and shadow detail. Very interesting.

[Nick Outram]

Originally Posted by Gian Pablo Villamil

Very useful, thanks! I will repeat your experiment with my A1.

I suspect that they are playing with gamma curves to maintain/enhance highlight and shadow detail. Very interesting.

Hey guys, just got back from the pub (well, I have to have some sort of life outside this wonderful forum :o)

Stu: will re-read your post when I can gofus better of the words...

Gian: I think Gamma curves are a bit beyoond the HC1 but u can do it in post. Of course you aint captured enough bits by then but hey, who will notice! hehe. OK, better go now, its 1.40am and I am at work @ 9.00am.

Weekend coming, more experimentation -keep posting GUYS! Good night!


|||Nick.

[Lou Squitieri]

Stu,
Nice job!

[Michael Stowe]

Great work Stu. I, like you, do not understand how this is possible without exposure change. Really....I cannot see any way of doing this without some built in filter that we are not aware of. There are, of course, similar settings with DSLR cameras and I have reproduced all with using manual functions on board. If, in fact, there is some extra thing the camcorder is doing then I would be in amazement of that. I really do not trust the readings that the data code gives for anything on the A1 after experimenting myself. Hopefully there will be an answer to this. Without some extra filter settings I cannot believe these settings cannot be achieved manually. I may very well be wrong which is the case many times, but without an advanced filter...hmmm.

P.s. Gain limitations being the exception...that is great.

[Graham Baker]

A lot of Sony & Panasonic camcorders have built in ND filters that slip into the light path without telling the user - the actual range of the mechanical iris is quite small on these small lens assys - perhaps F2 - F5.6 (refraction is a real problem at small apertures on small chips like these) and after that more obscure methods are used to limit the amount of light...

[Stu Holmes]

Originally Posted by Graham Baker

A lot of Sony & Panasonic camcorders have built in ND filters that slip into the light path without telling the user - the actual range of the mechanical iris is quite small on these small lens assys - perhaps F2 - F5.6 (refraction is a real problem at small apertures on small chips like these) and after that more obscure methods are used to limit the amount of light...

Very true Graham.

HC1/A1 have i think 2 or 3 internal ND filters that move in and out of the optical path. Camera is not keen to physically stop-down further than f4.
So it starts using ND filters - it even will use PARTIAL ND filter. i.e. move it partially into the optical path (apparently).

As Gian said, I think that Sony play with the gamma curves for definite with these programs. You can see visible changes, but the reported aperture, shutter, gain does not change and to me it just looks like they've programmed some of these 'Program AE' modes and moved gamma up or down.
I think they've done this in modes like the Portrait and Spotlight modes. SOMETHING changed but it was subtle and tended to affect shadow areas - i suspect a programmed (non-user-configurable) gamma change.