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Thread started 16 Jul 2015 (Thursday) 20:29
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7D 1 Underexposure - Again

 
Pagman
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Jul 21, 2015 11:09 |  #211

BigAl007 wrote in post #17639016 (external link)
If you are shooting RAW, which you are then the 160, 320, 640 ISO settings give you NO SNR ADVANTAGE. Just shoot the shots using the same exposure time and aperture value you would have used for them, but expose at ISO 200,400,800. Of course you could also shoot using values for ISO 80, and expose using ISO 100. By allowing the camera to make the digital exposure pull to create the intermediate ISO values you are giving up the additional control that you would have doing the same thing in your RAW processor of choice. The camera makes a linear adjustment to create those 1/3rd stop ISO values. When you do the same in your RAW converter there is nothing from stopping you using any shaped curves adjustment you want, so you could for example pull the highlights, while leaving the shadows alone, which is one effective way of boosting shadow detail, without adding additional noise. Also remember that although those intermediate ISO settings, for a processed image have a higher SNR, they also have less dynamic range.

It is actually really simple when it comes to shooting in RAW, if you have a choice between doing something digitally in either the camera, or on the computer, do it on the computer. You will have more control.

Alan


Thanks Alan, what in your opinion would be the absolute cleanest ISO speeds if exposed with out under exposing? are you saying that the generic camera standard ISO speeds of 100,200,400,800,1600 are the best and cleanest regardless of DR.

P.


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BigAl007
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Jul 21, 2015 11:25 as a reply to Pagman's post |  #212

The Unexpended range from 100 up to whatever, will always produce the best results, provided YOU expose and process the images to best advantage. The best SNR/DR combination is going to be found at ISO 100, however in a situation where you cannot either open the aperture up, or extend the shutter time, then you MUST increase the ISO, as the analogue amplification although reducing SNR and DR, will still be better than adding digital gain to the system to combat underexposure. So analogue ISO is fine, +1/3 rd digital ISO is BAD, and +2/3 ISO is pointless, as post will do it better.

Pagman read the following paragraph then forget it, it is of no practical use to you! It does though explain why when using an in camera conversion those other ISO settings have an advantage:

All of this presupposes that you are shooting RAW. If you are shooting in camera JPEGs then things change, that is when those +2/3rd ISO values become useful. They have better SNR's because they are effectively doing a little bit of exposure to the right.

Alan


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kcbrown
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Jul 21, 2015 12:05 |  #213

Pagman wrote in post #17638758 (external link)
Kc I dont think 100 would be achievable while needing a high shutter speed even at f5.6, i have not seen this possible much apart from when the sky and lighting has been very bright.

I realize that. But the planes you're photographing are quite distant, so the amount of motion you're attempting to freeze isn't so much that you need a really high shutter speed. Image stabilization will take care of the camera shake. I'd estimate you'll be at shutter speeds around 1/100th of a second.


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windpig
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Jul 21, 2015 14:34 |  #214

BigAl007 wrote in post #17639061 (external link)
The Unexpended range from 100 up to whatever, will always produce the best results, provided YOU expose and process the images to best advantage. The best SNR/DR combination is going to be found at ISO 100, however in a situation where you cannot either open the aperture up, or extend the shutter time, then you MUST increase the ISO, as the analogue amplification although reducing SNR and DR, will still be better than adding digital gain to the system to combat underexposure. So analogue ISO is fine, +1/3 rd digital ISO is BAD, and +2/3 ISO is pointless, as post will do it better.

Pagman read the following paragraph then forget it, it is of no practical use to you! It does though explain why when using an in camera conversion those other ISO settings have an advantage:

All of this presupposes that you are shooting RAW. If you are shooting in camera JPEGs then things change, that is when those +2/3rd ISO values become useful. They have better SNR's because they are effectively doing a little bit of exposure to the right.

Alan

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DreDaze
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Jul 21, 2015 14:47 |  #215

What's SNR? I can't figure it out


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windpig
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Jul 21, 2015 14:52 |  #216

signal to noise ratio


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TeamSpeed
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Jul 21, 2015 15:30 |  #217

Pagman wrote in post #17638754 (external link)
Skip, the idea is to pull the exposure back down in post, isnt this the basis of how ETTR is done with all subjects, starting with an over exposed shot then pulling it back afterwards, capturing the fine detail but without noise?

P.


ETTR isn't about overexposing. It is about putting your brightest highlight that you don't want to blow out to be on the right side of the histogram using its native analog ISO ranges. Sometimes, that part of the photo isn't the brightest area in the photo, but rather the subject material. For example, if you shoot this way where a plane is lit by the sun, depending on the sky, you may blow out the sky completely to get as noise free an area on the plane. You can just brighten the shadowed plane if you don't do this, but you will introduce more digital noise that way, than potentially doing ETTR.

Doing any brightening or darkening after the fact in a raw editor or JPG editor is nothing more than a digital manipulation as opposed to doing this in the camera utilizing its analog capabilties, provided your ISO isn't an expanded ISO value. You want as much analog processing as you can get, before you move into the digital (ie. mathematical) manipulation. Extended ISOs effectively do pushing or pulling for you, saving you a bit of time, but if you shoot raw, there is no advantage that I am aware of.

Daniel Browning has an interesting post here somewhere on this that describes analog ISO control vs mathematical control, using Numpty ISO values etc. :)


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Pagman
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Jul 21, 2015 15:55 |  #218

How would ETTR or any of the exposure control come into affect in fast environments like Airshows etc? I have been in situations like this in the past including Heathrow Airport when you could spot planes from a special viewing area inside the complex, when I used to go then when you wanted to get as many photos as possible - you had no time to mess with your camera or meter the scene, our cams where used more like PAS cams just snap snap snap in various lighting conditions, one minute loads of sky in the shot, the next a ground shot including buildings, and the next into the sun.
I would imagine it is like that at some of the very big airshows with lots of fast action going on, and trying not to miss anything, with your cam primed for everything, again In the past I have done loads of shows like that, one minute using the 70mm end of my zoom for a staic plane, then quickly turning round to catch a plane blasting off the runway, so it was a case of quickly turning extending the lens to 300mm and fire off a couple of quick blasts.

This was the sort of picture taking I was used to - relying on the cam just to record the shot onto film under varying conditions all i auto mode.

P.


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patrol50
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Post has been edited over 2 years ago by patrol50.
Jul 21, 2015 16:40 |  #219

i truely admire your patience gents - 15 pages and 218 posts and this guy still doesnt really get it :rolleyes:- good trolling  :p


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Pagman
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Jul 21, 2015 16:50 |  #220

patrol50 wrote in post #17639413 (external link)
i truely admire your patience gents - 15 pages and 218 posts and this guy still doesnt really get it :rolleyes:- good trolling  :p


Give us all a break mate nothing to see with comments like that "jog on fella":lol:

P.


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LincsRP
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Jul 21, 2015 17:07 |  #221

I may have missed it after 15 pages but to be perfectly honest I'd suggest bracketing by 1/3 stops and see what works and then get the next plane with bracketing with 2/3rd stops until you find something that works.

I shot s spitfire over our home town a few days ago and didn't know (as I shoot sports) exactly what I was up against so, 10fps, bracketing by 2/3rds stop and got the image and now I know what works.

All this ETTR malarky and stuff just does fry my remaining brain cell :lol:


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patrol50
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Post has been last edited over 2 years ago by patrol50. 2 edits done in total.
Jul 21, 2015 18:11 |  #222

Pagman wrote in post #17639431 (external link)
Give us all a break mate nothing to see with comments like that "jog on fella":lol:

P.

mate you have been given 220 + posts suggesting the best approach some of them really excellent advice and still you troll on in the top few of the leader board - each time someone takes a small swipe at you you pull out the disability card with some success ( no offence ;-)a ) - just go learn the camera please - and just give it a break hey !!

cheers and best oh and hey - good shooting :lol:


C:- 7D Mk11 ; 7Dc ; 600D & SX10 IS / L:- EFS 10-22 f3.5-4.5 USM ; 55-250 f4-5.6 IS 11; 18 -200 f3.5-5.6 IS ; & EF 16- 35 f4 L IS USM , 24-105 f4 L IS USM; 70-200 f4 L IS USM; 100-400 f4.5-5.6 L IS 1 USM (V1 and V11); + C 1.4 Ext Mk3 & Tam 150 - 600 f5-6.3 DI VC USD.

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Pagman
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Jul 21, 2015 18:41 |  #223

patrol50 wrote in post #17639522 (external link)
mate you have been given 220 + posts suggesting the best approach some of them really excellent advice and still you troll on in the top few of the leader board - each time someone takes a small swipe at you you pull out the disability card with some success ( no offence ;-)a ) - just go learn the camera please - and just give it a break hey !!

cheers and best oh and hey - good shooting :lol:


220 pages of discussion mate and believe me i have been learning a lot - if you dont ask you never learn anything, all the constructive comments I have been given and advice where It to has been given - even if it has been repetitive, has been extremely useful.

I have learned more about my camera and photography in general from the past 220 odd pages than ever before.

The majority of the posters who have commented have been really helpful.

Apart from a few how can i describe them - ummm :-(;-)a;-)a;-)a

Good day to ya fella have a Fosters on me tu da ru

P.


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BigAl007
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Jul 21, 2015 18:52 |  #224

Pagman wrote in post #17639366 (external link)
How would ETTR or any of the exposure control come into affect in fast environments like Airshows etc? I have been in situations like this in the past including Heathrow Airport when you could spot planes from a special viewing area inside the complex, when I used to go then when you wanted to get as many photos as possible - you had no time to mess with your camera or meter the scene, our cams where used more like PAS cams just snap snap snap in various lighting conditions, one minute loads of sky in the shot, the next a ground shot including buildings, and the next into the sun.
I would imagine it is like that at some of the very big airshows with lots of fast action going on, and trying not to miss anything, with your cam primed for everything, again In the past I have done loads of shows like that, one minute using the 70mm end of my zoom for a staic plane, then quickly turning round to catch a plane blasting off the runway, so it was a case of quickly turning extending the lens to 300mm and fire off a couple of quick blasts.

This was the sort of picture taking I was used to - relying on the cam just to record the shot onto film under varying conditions all i auto mode.

P.


Set your exposure manually, based ideally on using an incident lightmeter, and away you go. Most summer airshows that i have been to in the UK, I have been able to set my exposure at the start of the show, and unless you have very broken cloud, the exposure at around 2pm will be pretty constant for the next three or so hours, certainly within a half stop. If the conditions to change, generally they are quite slow, and you will notice and re-meter for the changes conditions anyway. I have two main setups for airshows, the first is at 1/160 for propellor driven aircraft, the other for jets is 1/2000 or as close as I can get depending on lighting and maximum unexpanded ISO. Usually if it is sunny the 1/160 shot will need ISO 100 and about f/11 to f/16 which is pretty close to sunny 16 anyway. It would have to be quite exceptional conditions, which would actually affect the running of an airshow in all probability, to make the light change fast enough that one might actually want to use an auto exposure mode. It will take a strong wind to push the clouds along that fast.

Really the only time that this hasn't worked for me is when I have had a very thin layer of cloud that is directly backlit by the sun. This produces so much light, compared the the exposure that the aircraft would actually need that it starts to bleed across saturating the sensor with scattered light. In this situation it is pretty much going to be impossible to get any decent results. If you reduce the exposure to prevent the sky/scattering saturating the sensor you just end up with a silhouette with no detail at all. I have encountered this once at Duxford, when shooting aircraft out to the west of the airfield, as the crowd line runs roughly east north east to west south west with the crowd on the north side. The other occasion was at Seething an old WWII Liberator bomber base. At the show here the line runs a bit more north south and faces west. Here it wasn't so much cloud, but on a day with very little wind the white smoke from several aerobatic displays coalesced into a thin layer, with a little haze added in. In both cases shots in the general direction of the sun were affected, while anything away from the sun was fine. With blue skies you would need to have the sun fully in shot, and very close to the subject to get this sort of effect. With thicker cloud cover, the sun is obscured enough anyway to negate the effect.

I don't know how many times it has to be said to you that for aviation, and other backlit scenarios, auto exposure of any sort is not particularly useful, while full manual control is your friend. Yes you can force auto modes to work for you, but it is much harder work to do so. The biggest problem is that the amount of EC necessary will vary with the weather conditions. Blue sky will need one EC setting, bright white clouds will require another, while dark clouds will require yet a third. In the time it takes to make that decision on how much EC to apply, and then take the shot, you could have your manual settings set, including taking a meter reading, and still get the same shot. Its just a case of storing the camera with the most likely settings already set. If I am just expecting to want to take general photographs, not aviations subjects, in the summer I will leave my camera with my standard range zoom, set to ISO 100 Av mode with the aperture set at f/5.6 and with +1 stop EC as I prefer my images that much brighter than the ISO standards specify . In the winter that might be ISO 200 or even ISO 400, as the conditions are less likely to support ISO 100. This way I can grab the camera and have a good chance that the settings will produce a reasonable result, or only require a couple of clicks adjustment in either direction. In specific situations I will have already set up the camera with settings close to what I might expect to need to use.

Remember the six P's, Prior Planning Prevents Pi** Poor Performance.

Alan


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Pagman
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Jul 21, 2015 19:14 |  #225

BigAl007 wrote in post #17639576 (external link)
Set your exposure manually, based ideally on using an incident lightmeter, and away you go. Most summer airshows that i have been to in the UK, I have been able to set my exposure at the start of the show, and unless you have very broken cloud, the exposure at around 2pm will be pretty constant for the next three or so hours, certainly within a half stop. If the conditions to change, generally they are quite slow, and you will notice and re-meter for the changes conditions anyway. I have two main setups for airshows, the first is at 1/160 for propellor driven aircraft, the other for jets is 1/2000 or as close as I can get depending on lighting and maximum unexpanded ISO. Usually if it is sunny the 1/160 shot will need ISO 100 and about f/11 to f/16 which is pretty close to sunny 16 anyway. It would have to be quite exceptional conditions, which would actually affect the running of an airshow in all probability, to make the light change fast enough that one might actually want to use an auto exposure mode. It will take a strong wind to push the clouds along that fast.

Really the only time that this hasn't worked for me is when I have had a very thin layer of cloud that is directly backlit by the sun. This produces so much light, compared the the exposure that the aircraft would actually need that it starts to bleed across saturating the sensor with scattered light. In this situation it is pretty much going to be impossible to get any decent results. If you reduce the exposure to prevent the sky/scattering saturating the sensor you just end up with a silhouette with no detail at all. I have encountered this once at Duxford, when shooting aircraft out to the west of the airfield, as the crowd line runs roughly east north east to west south west with the crowd on the north side. The other occasion was at Seething an old WWII Liberator bomber base. At the show here the line runs a bit more north south and faces west. Here it wasn't so much cloud, but on a day with very little wind the white smoke from several aerobatic displays coalesced into a thin layer, with a little haze added in. In both cases shots in the general direction of the sun were affected, while anything away from the sun was fine. With blue skies you would need to have the sun fully in shot, and very close to the subject to get this sort of effect. With thicker cloud cover, the sun is obscured enough anyway to negate the effect.

I don't know how many times it has to be said to you that for aviation, and other backlit scenarios, auto exposure of any sort is not particularly useful, while full manual control is your friend. Yes you can force auto modes to work for you, but it is much harder work to do so. The biggest problem is that the amount of EC necessary will vary with the weather conditions. Blue sky will need one EC setting, bright white clouds will require another, while dark clouds will require yet a third. In the time it takes to make that decision on how much EC to apply, and then take the shot, you could have your manual settings set, including taking a meter reading, and still get the same shot. Its just a case of storing the camera with the most likely settings already set. If I am just expecting to want to take general photographs, not aviations subjects, in the summer I will leave my camera with my standard range zoom, set to ISO 100 Av mode with the aperture set at f/5.6 and with +1 stop EC as I prefer my images that much brighter than the ISO standards specify . In the winter that might be ISO 200 or even ISO 400, as the conditions are less likely to support ISO 100. This way I can grab the camera and have a good chance that the settings will produce a reasonable result, or only require a couple of clicks adjustment in either direction. In specific situations I will have already set up the camera with settings close to what I might expect to need to use.

Remember the six P's, Prior Planning Prevents Pi** Poor Performance.

Alan


Thanks Alan,

Yep I will be using manual for all my shots as I was in my d7100, you mention f11-f16 above - doesn't that affect diffraction, as i thought that can creep in with crop cams anywhere past f10 or so sometimes less?

Hey Seething - visited there back in the 80s in fact a bunch of us spotters did a weekend trip all over East Anglia and the South East, it was brill we camped in the forest by Mildenhall to get the SR71s that where there.

Happy days:-):-):-)


P.


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