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Backlight & contrast

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jaxtion25
 

Backlight & contrast

Post Mon Jun 01, 2009 11:30 am


Does anyone know how to increase contrast in backlighting scenes? either during shooting or in PP without increasing noise level (too much).
Like the one shown below, it was shot at 1/125s f/2.8 iso500 but as a result of adjusting levels the noise level increased significantly. It now looks like iso1600. Adjusting level was all i did to increase contrast.


pstubley
 
Posts: 217

Re: Backlight & contrast

Post Sat Jun 20, 2009 2:38 am


This is a nice shot, and I don't mind the grain. I'm not sure if I have any brilliant suggestions, but here are some things you might try:

1. Curves can give you a little more control than levels to adjust contrast. The curves approach lets you change the slope without necessarily stretching the dynamic range as much, so there may not be quite as much noise.
2. I assume you shot in colour. Did you adjust contrast in colour, or after you converted to gray scale? Much of the noise seems to end up in the blue channel, so starting in colour might let you manage it easier.
3. There are several third party noise filters -- I use the one from Imagenomic, but there are lots of good things said about Noise Ninja as well. They can be very effective at removing this amount of grain. They can be done at the colour level and at the b&w level (before or after conversion).

I don't know of anything you can do in the camera. I wish I did. Ansel Adams used to tweak the processing of the film to take full advantage of the dynamic range, but I don't know how to adjust that in the camera. We'd have to be able to change the sensitivity curve of the sensor, and they don't give us a knob for that. But if anybody has any tips for that, I'd love to know what they are. We have HDR to deal with a wide dynamic range scene, but I don't know what we have to expand the range of a narrow dynamic range scene.

The only other thing I can think of might be a little fill flash, but the sense of light in this shot is so nice already that fill flash might just ruin it. And lose that nice spontaneous feel it has.

Good luck, and thanks for sharing this shot.

Peter

jaxtion25
 

Re: Backlight & contrast

Post Tue Jun 30, 2009 11:26 am


Hey thanks for replying. This was a while ago, I tried a number of different post process techniques, some as you suggested. I've come to conclude post process won't reduce noise, it has to be done during the shoot. The dynamic range between the foreground and background is too great, like maybe around 3-4 stop difference. You were right to suggest fill-in flash and also right to point out it'll ruin this type of shot because it'll lose the spontaneous feel. I think i'll just have to put up with the noise, haha.

prinothcat
 
Posts: 662

Re: Backlight & contrast

Post Tue Jun 30, 2009 11:18 pm


I would add that a ND Grad filter would help somewhat with the dynamic range, but again at the cost of spontaneity. It has been said that one of the sacrifices we make when shooting digital, is dynamic range. Film had it to start with, it could be played with in the darkroom, both with the film and the print. Digital just doesn't have as much of it to start with, so no amount of tweaking will make up for what is not recorded. I like the image as it stands.

dougj
 
Posts: 2276

Re: Backlight & contrast

Post Wed Jul 01, 2009 12:47 am


You're limited in approaches with this type of shot due to the high DR. The suggestion to use fill flash is a good one, when setup correctly it will not look like flash was used as the camera will use both ambient and flash for the light sources, and it can be just as fast and spontaneous as a natural light only shot. I'm not familiar with Nikon, but in Canon land, the Av mode is fill flash when a flash is present& turned on, this can be either the built in flash or an external one. I think you could reduce the exposure compensation by 1 - 1-1/2 stops for the background and offset this with a little flash.

I also agree with Chris, it's a nice shot as is, some overexposed areas can add to the artistic appeal of a photo.

jaxtion25
 

Re: Backlight & contrast

Post Wed Jul 01, 2009 11:57 am


@ prinothcat : Interesting to suggest ND filters. I have no experience with them, but from what I know, they reduce light by 1/2/4 stops? Would it only reduce light in the background in this case? I would have thought it'd take light out of the entire frame.

@ dougj : Yes Nikon has fill-in flash as well, but it would have changed the tonal texture of the face. So what kind of setup is required to make it look natural? I should point out i didn't have any other equipment with me at the time. Would it have been possible with onboard flash?

dougj
 
Posts: 2276

Re: Backlight & contrast

Post Wed Jul 01, 2009 1:06 pm


The fill flash will provide some light for the front of the subject, the key is to not overdo it so it becomes a flat flash shot with blown facial areas. It will also remove some of the shadows. For a relatively close shot like this the onboard flash should be OK. I typically use a negative flash compensation of -1.5 to -2, this depends on the flash, distance, etc. You can do a little experimenting without your subject/model using different settings and then go live. This is still a difficult shot, if you're familiar with shooting in Raw, you can recover maybe 1 EV of the highlights in post processing with a little work in Photoshop. I tried some levels and gradients on your shot, but there wasn't enough there to make a significant difference. I don't do much portraiture, but close ups of perched birds with the sun overhead or in the background creates some similar challenges. This shot is still nice as it is.

prinothcat
 
Posts: 662

Re: Backlight & contrast

Post Thu Jul 02, 2009 11:40 pm


jeffery wrote:@ prinothcat : Interesting to suggest ND filters. I have no experience with them, but from what I know, they reduce light by 1/2/4 stops? Would it only reduce light in the background in this case? I would have thought it'd take light out of the entire frame.

Yes you have that correct a full ND would drop the EV over the entire frame.. The ND graduated filter (ND grad), however, only darkens one half of the frame. They come in hard or soft transitions. A full frame style is available as well that goes full dark on one edge to clear on the other. I prefer to use square filters, in a Cokin holder that rotates freely in front of my lens so that I can adjust where the transition falls, simply by turning the holder and sliding the filter in and out of the holder.. In theory at least you could have lowered the exposure value for the top right corner with a judicious alignment of a Grad. As far as the actual filters go, Cokin are an inexpensive to learn how they work. The draw back of Cokin I have found is that they are not color neutral, for some reason they have a subtle red coloration. They do make a very useful holder however, and most every other maker has filters that fit that Cokin frame.

I'll also chime in on the fill flash idea, and suggest that a slow sync setting, or slow rear setting may help as well since the primary exposure is metered then the flash fires to make up for the (in your case) backlighting. These allow the metering system to make the best exposure it can off of the ambient light then provides the fill. Both should also allow the blur from the motion of her arm, helping to eliminate the strobed look.

jaxtion25
 

Re: Backlight & contrast

Post Sat Jul 04, 2009 8:53 am


@ dougj: Hey thanks for the suggested settings! I will try them out next time i'm shooting in this lighting scene again. By the way, this was shot in RAW and even at -1EV it didn't recover much at all, hence the decision to go white-out. Shows you how much difference in dynamic range existed!

@ prinothcat: That graduated ND filters sound very interesting indeed, i think i'll get me some. Yes i have heard it is better to get the ones with sliding filters with holders instead of screw-on ones. Though i do wonder how much it would help in this particular scene, since i'm looking for methods to reduce noise. Reducing amount of light with ND filters i imagine i would have to up the ISO, which would result in same amount of noise!

prinothcat
 
Posts: 662

Re: Backlight & contrast

Post Sat Jul 04, 2009 1:33 pm


jeffery wrote: Reducing amount of light with ND filters i imagine i would have to up the ISO, which would result in same amount of noise!

ideally maybe you will not since with the grad you're only lowering the the EV in the "hot" corner. The rest of the image stays the same. By lowering the EV in the upper right, you probably eliminate most of the noise from the hot spot. The art in the technique is finding the magic spot to place the transition.

jaxtion25
 

Re: Backlight & contrast

Post Sat Jul 04, 2009 11:20 pm


ohhhh i see, that is magic. ill definitely try out this graduated ND filter sometime!

prinothcat
 
Posts: 662

Re: Backlight & contrast

Post Sun Jul 05, 2009 1:48 am


jeffery wrote:ohhhh i see, that is magic. ill definitely try out this graduated ND filter sometime!

it's one of those things that seems to make sense in writing, and once you pick one up and see how they mount to the front of the lens a light goes on and you have one of those AH HA moments.... They become very useful for landscape work where you have bright blue sky and white clouds, and your foreground has shadow details that you just can't get to come around. The Cokins, their noted short coming aside are a good inexpensive place to start, then you can look into the higher grade glass filters once you find the ones you use most often. I have a full set of Cokin resins, and now know I only really use three of them. One hard transition, a soft transition both ND4 I think, and an ND 8 full grad. These will be replaced with B&H or something comparable as $$ allows.

As an example this was shot with a soft transition ND4, the transition was paced on the skyline, to bring out he clouds, while exposing for the reds and oranges of the foliage. There are other examples in my galleries, some are identified in the notes.

benjikan
 
Posts: 344

Re: Backlight & contrast

Post Wed Jul 15, 2009 10:36 am


jeffery wrote:Does anyone know how to increase contrast in backlighting scenes? either during shooting or in PP without increasing noise level (too much).
Like the one shown below, it was shot at 1/125s f/2.8 iso500 but as a result of adjusting levels the noise level increased significantly. It now looks like iso1600. Adjusting level was all i did to increase contrast.



If you wish to accomplish more contrast in PP in this scene, I suggest using the Shadow/Highlight filter in Photoshop. You will be able to bring out more of the details.

You may also wish to employ one of my Post Production techniques which will give a lot more "Pop" to your image.

http://www.benjaminkanarekblog.com/?p=192

Ben :)

jaxtion25
 

Re: Backlight & contrast

Post Mon Jul 20, 2009 8:58 am


Hi Ben, thank you very much for your reply and i apologise for not seeing this sooner. i had a look at your post process technique, i think it's very useful, but not for this particular shot. I'm not quite looking to give this image more 'pop', i think it's got enough of it already but rather to increase contrast from the original without exacerbating noise in the process. I believe the other guys were right to suggest additional lighting aids during the actual shoot than attempt to create the contrast in PP.


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