Understanding your camera’s built-in metering system

number six wrote in post #3389251
More than one way to skin a cat. A little PP improves things substantially.

(Please ignore the jpeg degradation - I modified and resaved the file which was already compressed about max for good quality on the web.)

In many cases like this I don't have time to compose carefully and examine histograms, since I'm sitting on the bike with my helmet on.

-js

Hi js,

I was hoping we wouldn't go there... LOLOL
I firmly believe that post processing should be a last resort but I did want this thread to be about exposure and understanding how to properly expose a shot in-camera.

lcfr-nl437 wrote in post #3389096
Brian Petersen's book - "Understanding Exposure" is a great book to help learn this subject. I have enjoyed it immensely!

I just got this book and am looking forward to a few hours with it.

TMR Design wrote in post #3389345
Hi js,

I was hoping we wouldn't go there... LOLOL
I firmly believe that post processing should be a last resort but I did want this thread to be about exposure and understanding how to properly expose a shot in-camera.

I'm with you 100%. As I mentioned, many of my riding pics are (as it were) shot from the saddle. Often I can't see the viewfinder very well with my helmet on. Still, I don't have time to take it off because the other hooligans are disappearing into the distance while I'm shooting.

Wild Bill Hickock would understand.

As I've said in a number of other threads, correct exposure eliminates many problems.

I'm not a member of the RAW religion, many of whose acolytes apparently trust in RAW to deal with their exposure errors.

Ummm, did I say something inflammatory?

-js

BTW, my first pic here (the S curves) is one of my favorites.

Classic case of the vanishing point - it doesn't have to be straight lines!

-js

Two thoughts:

1. This particular shot is a great example of why I'd love to own a nice GND filter sytem.

2. Who out there actually uses exposure compensation? I've found it to be a pretty useless feature. If I want the exposure brighter or darker straight out of the camera, I adjust my shutter speed to be higher or lower of the meter's center point. If that fails to produce the image I want, it's usually not to the point where the highlights or shadows are irrecoverably lost and I straighten it out in PP.

Obviously, adjusting shutter speed has implications other than exposure levels if shooting fast-moving subjects, but isn't exposure compensation a factor independent from the data captured by the sensor? In other words, isn't it always adjustable in PP with the same results as adjusting it on the camera?

Robert- Sorry I had to bail on you after my last post trying to help build where you were going with this tutorial; I had to take my sister to the hospital and didn't get home until 3am.

My thoughts on the last 9 hours of posts:

- Understanding Exposure leaves A LOT to be desired. It's a good starting point with images that do a good job of explaining the relationships of ISO/Av/Tv. But when it comes down to a lot of the details about when and how much +/- EC to use for what types of scenarios it is incomplete. It describes what each metering mode does but never mentions when each it is appropriate to use each metering mode. In essense it is an incomplete book that will leave the reader feeling great about their new found ability to properly expose images until they start shooting real world images and failing to get their intended exposures.

I posed my questions in post 5 with the hope that this thread would start giving the rules or guidelines for EC for varying types of scenes where Bryan's book basically just touches and then falls short.

Robert- perhaps we can create a new thread of 30 or so properly exposed images that required +/- EC and give people a chance to study the image and determine how much EC, if any, should be applied to the image (assuming evaluative metering). If we post one image per day and give the answer and explanation as to why the following day by the end of a month most readers will instinctively understand what compensation should be made to the camera's metering. Future month's lessons could take a similiar approach but with spot metering for example. The question we might ask would be what object/section of this image would you spot meter from?

Number 6's 2nd image is a great example of a lesson on how to look thru your viewfinder and recognize how great the dynamic range you need to capture an image, knowing the dynamic range your DSLR is capable of capturing, and how to handle situations where the DR of an image exceeds your camera's DR. Understanding how to compute the difference in stops between the highlights and shadows will tell you what type of Neutral Density filter is appropriate to capture everything in one image.

Keith- Spot metering would not have helped here. Reguardless of what you choose to make middle grey there is still too much dynamic range in the picture to be captured by one DSLR image. A GND filter would still be required to bring the picture into the DR of the sensor. Once you put on a GND filter you don't have a metering nightmare and can use the metering mode of your choice to capture the shot.

Logan- The answer to your second question as to who uses EC is anyone who is shooting in Av or Tv mode that wants proper exposure when the camera's meter is fooled by a scene. If you are shooting in Manual mode then the approach to adjusting above or below is the way to accomplish it as you point out.

The goal of Robert's posts and my comments has been to get correct exposure in camera rather than relying on PP just as one should frame their image in camera rather than relying on cropping. It's great we have PP to cover our mistakes but we shouldn't allow ourselves to be sloppy and rely on them any more than someone should use overdraft protection v. reconciling their bank statements. We also only get +/- 2 stops of EC with our RAW conversions so getting as close to perfect an exposure in camera will allow us to stay within the confines of what we can correct.

RichNY wrote in post #3390637
Robert- perhaps we can create a new thread of 30 or so properly exposed images that required +/- EC and give people a chance to study the image and determine how much EC, if any, should be applied to the image (assuming evaluative metering). If we post one image per day and give the answer and explanation as to why the following day by the end of a month most readers will instinctively understand what compensation should be made to the camera's metering. Future month's lessons could take a similiar approach but with spot metering for example. The question we might ask would be what object/section of this image would you spot meter from?

I second this idea! As my previous post shows, I'm not certain about the functionality of EC.

Newbie Alert!!!!
I fully understand the concept, I can just never remember what metering modes symbols are for what metering really bugs me

Robert, Rich and all thanks so much for your comments. They are helpful for newbies as well as seasoned photogs.

Rich, I hope your sister is doing well.

I would love to see a monthly tutorial of sorts as exposure is the key to the pic, or at least what you want to say with it

I really appreciate the information. One of the things that makes POTN such a great site is that there are so many people willing to share their knowledge.

Logan7 wrote in post #3390570
Who out there actually uses exposure compensation? I've found it to be a pretty useless feature. If I want the exposure brighter or darker straight out of the camera, I adjust my shutter speed to be higher or lower of the meter's center point.

I do. You're describing manual exposure, which I use only when circumstances require it. I normally use P, not Av or Tv, because I can get the same effect by letting the camera determine exposure, then spinning the dial to get the aperture I want, then adjusting the EC.

I find this sequence to be fastest - which matters to me because often I shoot while sitting on the bike, wearing my helmet and one glove.

What circumstances require manual exposure? It's absolutely necessary for panoramas, I've found.

Logan7 wrote in post #3390583
What did you do differently between the two shots? I'm pretty new to this, and I don't understand how you properly exposed the foreground without blowing out the background. The only thing I could think of is using a flash with an exposure longer than the flash duration (I'm sure there's a more proper term for this, but I don't know it). I'd love to know the answer, because I come across a lot of situations with dynamic lighting similar to this one.

It's just one shot. I post-processed the second one to increase brightness in the shadows. As Rich observed, the range of brightness in the scene is beyond the capabilities of the camera's sensor.

-js

Logan7 wrote in post #3390570
Two thoughts:

1. This particular shot is a great example of why I'd love to own a nice GND filter sytem.

2. Who out there actually uses exposure compensation? I've found it to be a pretty useless feature. If I want the exposure brighter or darker straight out of the camera, I adjust my shutter speed to be higher or lower of the meter's center point. If that fails to produce the image I want, it's usually not to the point where the highlights or shadows are irrecoverably lost and I straighten it out in PP.

Just about every photographer out there, from point and shoot to DSLR user.

Logan7 wrote in post #3390570
Obviously, adjusting shutter speed has implications other than exposure levels if shooting fast-moving subjects, but isn't exposure compensation a factor independent from the data captured by the sensor? In other words, isn't it always adjustable in PP with the same results as adjusting it on the camera?

Hi Logan,

Based on the above statements it would seem that you don't understand exactly what EC is and what it means to apply EC and perhaps don't completely understand exposure. Don't you realize that if you're adjusting your shutter speed from the camera's 'suggested' exposure (meter needle centered) that you ARE applying EC? Why do you only adjust shutter speed? Do you also realize that you can adjust your aperture to accomplish the same thing? Whether your compensating with shutter speed or aperture, if you're deviating from what the camera suggests then you're adding EC. If you went out shooting a variety of scenes and centered the needle for every one of them I can guarantee that your keeper rate will be low, and a good portion of your photos will have to be post-processed. So what do we do? Apply EC.

Post processing should be a last resort. Doesn't it make sense to you that it's simpler and better to nail the shot in-camera knowing you got the shot because of your knowledge rather than having to do post processing to recover highlights or shadows? Why go through that when 95% of the time you have the tools to get the shot right in the first place?

If you've read this thread carefully and looked at the images then you should understand that no matter what mode you're shooting in you need to understand how to apply EC to achieve correct exposures and compensate for the camera's inability to meter a complex scene.

Your comment about having shadows and highlights that can't be recovered is not correct either. If you blow out a sky you can't recover from that. There's noy way to turn a blown out white sky back to a blue one with white clouds. If you have shadows that have gone into black you can't recover fom that, and sometimes these conditons present themselves even when over or underexposed by 2/3 of a stop. It's not uncommon at all to have blown out skies and black areas in a shot where you've centered your needle. Once you leave that center position, again, you're applying EC.

So what you are classifying as a ueless feature is the exact feature that every single photographer uses on a daily basis to achieve correct exposures.

Not too long ago I participated and showed examples in another thread called Exposure Compensation. It might help you better understand EC and a little more about metering.

Hi Robert,

This is an excellent thread and i've added it to my favourites. I think this will develop as more people ask questions they feel haven't been answered. Well done!

Also, i'd definately agree with your statement about Understanding Exposure.

TMR Design wrote in post #3389155
Understanding Exposure is a great book and Bryan Peterson certainly does a great job of explaining exposure. Unfortunately he never ties it in with metering modes and never shows anything other than perfect exposures. This is the kind of subject that users benefit from seeing incorrect exposures and understanding why and what happened to make it an incorrect or bad exposure as well as seeing the correct exposure.

This is the one thing that has constantly thrown me off about the book
and i've tried at least 3 times to understand Bryan, but it hasn't helped.

Many thanks once again for making things much clearer than Bryan has ever done (for me at least)