Hmm, did it again

*Eaglerapids* · 04-25-2009, 07:52 PM

We have some Tundra Swans relatively close by so last weekend I went out to try to get some pics. I was unsuccessful getting anywhere near close to them but at one point a couple flew and I got off a few shots. I actually got a pretty cool shot or two but the birds were pretty blown out. I blamed myself. But I went back this morning and had a lot more chances. Still not really close but a lot better. I carefully checked the histogram frequently and, again, upon getting home and developing the pictures (I always shoot raw) I'm finding a lot of blown birds that just didn't show up in the histogram in the field.

Here his back is almost completely blown, I have applied no "recovery" in LR2. Not all were this bad but most all were blown. After last week I was carefully checking the histogram.
This kinda hurts, the weather is supposed to be lousy in the morning so it'll probably be another week before I can get back there.

I'm disappointed in myself that I didn't bracket my shots to be sure about these exposures, after all these are completely white birds, I should have known better....still making mistakes.

Man, these are some cool birds.

**Damn Brit** · 04-25-2009, 08:01 PM

Not sure if this is intended as a Post Your Photo or General Pentax Photography thread. I'm assuming the latter,let me know if you want it moved to PYP.

Maybe reflection off the water was screwing with your metering.

*Eaglerapids* · 04-25-2009, 08:07 PM

Gary, it started off with me complaining about the histogram not showing what actually was going on but after making my point I realized it was my fault. That's why I posted here, to bring to people's attention that the histogram in camera is not always right on or is not exactly right on depending on circumstances.......or something:-).

**Damn Brit** · 04-25-2009, 08:59 PM

Did you have blinkies on?

Now you've clarified, I've moved it back to DSLR section.

**roentarre** · 04-26-2009, 03:57 AM

The image has great feel to it. The sparkling of the water and the swan reflection makes it a winner image

*daacon* · 04-26-2009, 05:33 AM

I thought when shooting RAW the historgram was a representation of what the JPG would be ? Does a raw have a histogram ?

*Eaglerapids* · 04-26-2009, 07:29 AM

No, Gary, I didn't have blinkies on but I'm realizing I need to turn them on. On my K10D they are turned on and sometimes they are a hassle so I haven't turned them on on the K20D....yet.
Thanks roentarre, I got a bunch of images of this bird and his/her mate and all are blown to one degree or another. Grrrrrrrrr.
Daacon, I think you've hit the nail on the head. I remember a lot of discussions about this topic on the K10D but I just blindly followed the K20D's histogram in this somewhat extreme case (a white bird against a relatively dark background) and learned a lesson.

The images are still on the card, all I have to do is put the card back in the camera, turn on the blinkies and see but I'm pretty sure what I'll see..............durn it.

Quension · 04-26-2009, 09:31 AM

Originally Posted by Eaglerapids

I didn't have blinkies on but I'm realizing I need to turn them on. On my K10D they are turned on and sometimes they are a hassle so I haven't turned them on on the K20D....yet.

On my K200D, I turned them on only for the digital preview (instead of for playback), so they don't annoy me when I don't want them.

*Eaglerapids* · 04-26-2009, 03:32 PM

Of course the blinkies show the problem up in camera. Great idea Quension but I'm turning them on always because I can't trust myself.

pentkon52 · 04-26-2009, 04:06 PM

We have Trumpeter Swans at the farm we board our horses at. When i shoot them in water, i find it best at -0.3 or -0.7 EV, to avoid the burned out back high lights.

Dave

Dave

*Eaglerapids* · 04-26-2009, 04:29 PM

Pentkon, I was at -0.5 and it still wasn't enough. You know, everybody always wants faster FPS, 2300cross-type AF points (or whatever the hell it is they want:-)), please Pentax, give me the DR of film negatives, more latitude, please. If I needed 10 fps I could buy a Canon, they have the super duper telephotos that I couldn't afford to shoot sports and such. If Pentax could make a jump in dynamic range performance to go with the Limited and * lenses as well as all the old legacy glass, it would be HUGE.
I would love to see some of your Trumpeter swan pics:-). The differences between the Tundras and Trumpeters are relatively small, both are very impressive birds.

Duplo · 04-26-2009, 05:33 PM

Originally Posted by Eaglerapids

-Snip-
I'm finding a lot of blown birds that just didn't show up in the histogram in the field.
-Snip-

Above quote seems to be the core of your question.

There are two possible culprits, your RAW developer or your camera settings (not exposure, but tone curve, WB etc.).
The likely explanation is a little of both.

while I am not nearly technically knowledgable enough to go into details here is the reason and the steps to get an accurate RAW Histogram in Camera.

Now, I have not tried this on a pentax body, so certain steps may or may not be possible.

The RGB histogram displayed on the camera is from the JPG file embedded in the RAW file based on your in camera jpg settings. thus it is very different from the acutal RAW capture and what the sensor "sees".
2 primary things affects it. White balance and tone curve applied by the camera.

Now the Sensor itself has different sensitivities by default per colourchannel.
If you know these you will be able to find a default WB setting, generally called uniWB that reflects how the sensor sees the 3 colour channels.
This will get you a screwed up looking imagepreview WB wise, but will reveal how the sensor sees the scene and the ratio between the 3 colour channels.

Step two is to make sure that you have a linear tonecurve used in camera, to make sure that your histogram is not misleading. I have yet to own a camera that has one built in and on my nikon bodies the neutral setting does not equal a linear tone curve and my assumption is that this is a general thing across brands.

Now with the above two things handled you will get a fairly accurate histogram display of the actual RAW you have captured, but the imagepreview on camera may look more than a little odd.

Now this actually opens up a new use of colour correction filters to make sure that all 3 colour channels are exposed to the right, but that is taking things to the limit in terms of optimising your RAW capture. but none the less I have gone this route to optimise my RAW files for critical landscape work. It means more PP work, but there is something to gain.

Now with that in plase, mae sure that your RAW converter uses a linear tone curve too.

My silient prayer to the manufacturers would be to include a linear tone curve and a uniWB setting in the camera, but so far I have heard of anyone doing it.

If you want more reading and detailed how to, then do a search on DPR on Iliah and julia borg, they are probably two of the most knowledgable people on the subject I have come across. the hompage www.libraw.org is where you will finde some rather lengthy articles by the same people on the subject (and many other subjects).

*Eaglerapids* · 04-26-2009, 08:22 PM

Duplo, thank you for the info and good to see you around. I'm off to do a bit of research.....

Duplo · 04-27-2009, 02:48 PM

Originally Posted by Eaglerapids

Duplo, thank you for the info and good to see you around. I'm off to do a bit of research.....

You are most welcome

I am glad to be back again, time to upgrade some pentax gear in time for the big summer asignments, so I thought I would check back in

*jbinpg* · 04-27-2009, 04:37 PM

I find it useful to start a session with a "sunny 16 rule" shot. If it isn't sunny, then adjust for EV. That gives you a poor man's incident light reading shot which is where you should be heading in difficult lighting conditions.

Jack