View Full Version : Ben Franklin Bridge HDR
03-31-2008, 06:51 AM
This is my second attempt at HDR.
03-31-2008, 08:29 AM
I think you are "five and diming" the process, in regards to the Ben Franklin Bridge ... you need to shoot some extreme exposure to really get any impact out of HDR, as far as I have been able to determine.
Try two f-stops higher and two lower.
Use an electronic release cable (is there any other kind with a SONY DSLR?) if possible, to avoid moving the camera. (The DEATH of most HDR-shots)
Having an image of a subject that is so, rather ... silhouette ... tends to lack any real benefit from the HDR-effect. You do need some kind of "front lighting" to have a good chance at it. I could be wrong in this ... but, I believe the process calls for more production from extreme areas lost to normal exposure, ie., deep shaodws and near hightlights.
03-31-2008, 08:46 AM
I just wanted to try HDR. I did not take the pictures with the intent of doing HDR I just took the picture and bracketed the picture +-3 f stops.
03-31-2008, 02:12 PM
Well, that's a pretty substantial range ... one image would be nearly black and the other image blown-out white. Was that the case?
3 f-stop bracket
Your bottom shot -> f/2.8 ... normal exposure -> f/8 ... dark exposure -> f/22
or shutter-speed wise:
Your bottom shot -> 1/15 sec ... normal exposure -> 1/125 sec ... dark exposure -> 1/1000th sec
or, of course, the royal-favorite, ISO-wise (let there be noise!)
Your bottom shot -> ISO-6400 ... normal exposure -> ISO-800 ... dark exposure -> ISO-100
but, of course, we all know that 1600 is the most the α100 can do, so ... that's kind of out. Oh well ...
Anyway, could you post the "original three" shots, only smaller? I'm kind of curious. :D
The sensor can accurately discriminate about 1.5-f/stops above and below the exposure setting. So ...
given the brightest aperture we suggested f/2.8, you would see shadows accurately down to f/1.7
given the normal aperture we suggested f/8, you would see middle shadows down to f/5 and highlights up to /f/13
given the darkest aperture we suggested f/22, you would accurately see the highlights all the way up to f/44! Yeah, no kidding.
So, theorectically, your image should practically have about 9 f-stops of light bound into it, all the way from f/1.7 to f/44. That's even better than you can get from B/W film ... which is limited to seven f-stops.
03-31-2008, 06:12 PM
Don here are the 3 images I used.
03-31-2008, 07:27 PM
Okay, maybe it's me ... but, that cannot be three f-stops of difference ...
I'll pop some, tomorrow and confirm ... but, it looks more like 1 f/stop, either way.
Just for grins ... take a couple shots for me, tomorrow, of a tree in the yard at the following manual settings. Don't use A or S mode ... only M mode.
Using the 35-70mm f/4 lens
This lens can only go from f/4 to f/22, so we need to combo (using exposure math) up the settings a bit to get "effectively" the same exposure we need to demonstrate the effect.
Here's the list of shots and their settings:
Set the camera to the following:
. . . . Ap . . Sh Sp . . ISO
f/8 - 1/60 - ISO-200 "Normal" 0-f/stops
f/4 - 1/60 - ISO-400 "Over-exposure" -3 f/stops (simulate f/2.8 exposure, based on the first settings)
f/22 - 1/60 - ISO-200 "Under-exposure" + 3 f/stops
03-31-2008, 07:46 PM
I got the f-stops right from the picture info just like you told me. Is there another way to find out?
03-31-2008, 07:59 PM
I used the same lens ... and wound up with some very different looking levels of exposure. Of course, using it indoors ... my shutter speed was near 2 seconds ... but it demonstrated the different exposure enough to say your images are ... suspect. It might be 3 f/stops overall ... but not +/- 3 f/stops.
Things to consider ... faulty lens? The aperture blades aren't closing down as far as they should. It happens. They get some kind of "gook" on them and tend to stick to one another. Or perhaps the retracting spring won't open the aperture. I had this problem with one of my older TAMRON Adaptall2 lens. I simply could not get it down to its f/32 setting ... or have it back off to f/22, once it got down there. Really hard to get right with those old lens springs.
How old is that 35-70mm f/4 of yours?
As far as your images go, I cannot get EXIF data off the shots, as it has been lost in your reduction with your photo editor.
EDIT: Okay, I messed with what you provided in your earlier post. I took your darkest image and with the brightness slider, dropped it -50. I then took your brightest image ... and did just the opposite ... up +50. I left your "normal alone.
Here are the three "originals" ... the two after my brightness adjustment.
My attempt at HDR
That sky is "screaming!" :rolleyes: Check out those suspension cables ... you can see 'em!
Your original HDR
As I was trying to point out, the division of exposure made a lot of difference. I forced it to open wider with the brightness adjustment in Photoshop. It really made the sky "pop" and gives the bridge some "presense."
You had great positioning of the fence line ... and it underscores the bridge without ever running in to it. Excellent. In my attempt at HDR, with the brightness of the bridge corrected ... the bridge now becomes the subject and not the brighter fence line. Lokk at both, if you can ... and compare. You can just sense how your eyes lift from one HDR compared to the other ... just with exposure adjustment. The bright sky just pulls them up, like a magnet. Cool, huh?
03-31-2008, 08:58 PM
That is neat. With my HDR my eyes follow the fence to the bridge. I didn't want to crop out the fence and the walkway. You had me thinking for a minute. I am glad you asked how old my lens was. I thought the lens I was using was my 70-300 but I was using my 18-70 Sony kit lens which is brand new. How can I post the pictures with the EXIF data on them. I took a few other pictures that I set the bracketing to +-7 and I can see a big difference n the exposures.
04-01-2008, 06:10 AM
Okay, since you have explained that you did not MANUALLY bracket, but are using the α100's auto-bracketing feature, the camera is using only +/- 0.3 EV (EV = Exposure Value), not a full three f/stops, but 3/10s! Setting to +/- 0.7 EV or 7/10s increases that, but this is still not ENOUGH for a good HDR to be produced. It's not even a full f-stop. The fact is, the auto-bracketing feature is just enough to allow for bracketing of a typical shot, so you can quickly choose which one looks best for your use and print it.
To do an HDR ... you need to MANUALLY bracket (the camera cannot automatically do this with the range required), which means adjusting the camera through several individual shots ... on a tripod (no movement is critical) and with a release, if possible. You then adjust, as I stated earlier in this posting ... to allow for a full +3 EV and a full -3 EV (in fact +/- 2 EV may be enough), but not just 0.3 EV or 0.7 EV. Then, you will see the effect you are looking for.
I hope this clears this up. You need more EV variation.
04-01-2008, 09:37 AM
Can you manually set the camera to bracket the three shots and not use the auto bracket mode?
04-01-2008, 10:30 AM
That's kind of how they used to do it ...back before automated programs.
You simply need to calculate your settings for the level of EV you want to differentiate from.
Determine your proper exposure. You can use the camera's internal metering for this. Let's say you look through and find your shot is zeroed at the following settings:
f/8 - 1/125sec - ISO 200 <- "Normal" EV or exposure value
Take the shot.
Now, you want to bracket above and below this by +/- 2 EV
You have a couple of choices. You can use the same aperture ... thereby maintaining the depth of field (DOF). This is, perhaps, the most widely accepted method. So, you simply vary the time of exposure.
For +2 EV, the settings would be:
f/8 - 1/30 sec - ISO 200
For -2 EV, the settings would be:
f/8 - 1/500 sec - ISO 200
That's a quick way -> quadruple the exposure time, take the shot, and then cut the normal exposure time by a 1/4 and shot.
If you use the aperture setting to do it ... you will get a varied DOF ... and that can result in "special effects." It is an interesting look varying from f/4 to f/16, at the same speed and ISO.
For +2 EV, the settings would be:
f/4 - 1/125 sec - ISO 200
For -2 EV, the settings would be:
f/16 - 1/125 sec - ISO 200
That's the MANUAL method.
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