Yellow flower and metering off the sky

[Tobers]

I finished Bryan Peterson's "Understanding Exposure" book and went outside to try his "metering off blue sky" technique. Initially I thought this was just bonkers. I mean, how are you meant to get a correct exposure by pointing your camera up at the sky instead of at the subject you are wanting to photograph?

I put my cheapo 50mm 1.8 on my 30D and decided to have a wander around the garden and give it a go. And amazingly, it does actually work.

The thing about Bryan Peterson's book is that it very simply describes how to take a pic in manual mode. First, decide what aperture you want (i.e the depth of field on the pic). Then get a meter reading to determine the shutter speed. If you cant get a fast enough shutter, increase the ISO (or use a flash).

So I knew I wanted a very shallow DOF, with a blurry background, so set the aperture to 1.8. I found a suitable flower, pointed the camera up at the blue sky, set the pointy exposure meter in the viewfinder to be in the middle by twiddling the shutter speed, then took the shot (autofocus on the bobbly bits in the middle of the flower in this case).

I took quite a few pics using this method. Granted, you can just leave the camera on aperture priority mode, but if you are taking a pic of a white flower against a dark background the automatic metering can end up overexposing the white flower.

Anyway, very enlightening. I'm doing much more manual mode shots as a result of reading the book and I'm understanding more about what I'm trying to achieve as well.

Here's the pic...

Tobers

 

[stebbo2]

That's really nice. This book sounds like a good read, I have been hunting for a cheap second hand copy for a while now, but I might have to bite the bullet and get a new one.

 

[py6km]

Yes, that really does seem bonkers, but the resultant image is lovely. I'm going to have to get (and read!) this book.

 

[py6km]

Yes, that really does seem bonkers, but the resultant image is lovely. I'm going to have to get (and read!) this book.

Just ordered one from Amazon !

That's really nice. This book sounds like a good read, I have been hunting for a cheap second hand copy for a while now, but I might have to bite the bullet and get a new one.

Amazon have loads - in the used section there are loads of new ones for less than a tenner. I ordered a new one from the UK, but there are some even cheaper ones from the US.

 

[Yandros]

That's a gorgeous shot. I love the colour combination in particular.

Hmm, I have an old 35mm version of Understanding Exposure - must have another flick through.

 

[Tobers]

I was thinking I might sell mine after I've read it, but it's the sort of book you go back to time & again to read up on something specific. So it's staying with me.

It is a very good investment though - some really excellent photos in it and just the right level of technical detail in his writing. He explains the settings on each photo so by the time you've read it the technique has really sunk in. And I'm sure the non-updated (i.e. non digital) version is just fine as well - there is very little digital specific stuff in the latest revision, just the odd mention shoe-horned in here & there.

Oh - also, he talks about hyperfocal distance though he doesn't quite refer to it like that. He says "I manually focused to get everything further than 2 feet away in focus". How he knew what setting to focus to in each pic was a bit of a mystery, and there's only a brief bit at the end about it. Whilst out & about today though, I used my "photographers screwdriver" app which I loaded onto my mobile phone the other day to work out the hyperfocal distance of a few shots. Wierdly, whilst it looks blurred in the viewfinder, the shots were pin-sharp throughout their depth. Also, pressing the depth-of-field preview button shows the focus throughout the pic as well. Takes the guesswork away.

Tobers

 

[Deleted member 152499]

Whilst out & about today though, I used my "photographers screwdriver" app which I loaded onto my mobile phone the other day to work out the hyperfocal distance of a few shots. Wierdly, whilst it looks blurred in the viewfinder, the shots were pin-sharp throughout their depth.

Hi Tobers, I have also downloaded the Screwdriver app, which works well on my LG Prada BTW, but have little or no idea how to use it (or, if I'm totally honest, what it's used for )

You mention "pin-sharp throughout their depth" in your post.....can you give me some instructions as to why I would use this app, and perhaps more importantly, how I use the app?? Thanks in advance

 

[Tobers]

Yep - try this.

You want to take a landscape picture which is sharp right the way through the depth of the pic from the closest to the camera to the furthest distance. Let's say you are trying to emulate Liquid's or Vulkan's seaside shots.

Because you know that landscapes need some foreground interest, you've positioned yourself so there are some nice rounded rocks catching the light just in front of you. In the distance the sun is setting behind a lighthouse.

You need to get the close rocks and the lighthouse in focus. You set the aperture to be small e.g. f22. But where do you focus? If you focus on the lighthouse, the close-in rocks might be out of focus. If you focus on the rocks, the lighthouse will be out of focus. So what you need is the "hyperfocal distance", which will ensure that everything from that distance to infinity is in focus. You then dial that hyperfocal distance onto your lens (in manual focus mode) and you're sorted.

Because the lens stays wide open when you are focusing/composing to get max light through the viewfinder, and only stops down to your chosen aperture of f22 when it takes the shot, you wont know if everything is properly in focus unless you have a depth-of-field preview button which does stop the lens to your f22, and even then everything will look very dark through the viewfinder. This is why it is often easier to manual focus at the hyperfocal distance than autofocus on some arbitary point (often 1/3rd of the way into the picture).

So, using the little phone app:

- select "options" and select the crop size of your sensor (e.g. 1.6 on my Canon 30D, 35mm if you are lucky enough to have a full frame 5D or 1Ds).
- go to "depth of field".
- Enter the focal length you've set your lens to in your beach composition e.g. 10mm using a Sigma 10-20 lens.
- Enter the distance of the nearest thing you want in focus (the rocks) e.g. at 1m away
- Enter the aperture e.g. f22.
- Click OK. The app will say that your hyperfocal distance is 0.24m. This is what you dial into your focal ring on the lens.

The app will also say that your nearest focus is 0.19m away, and the furthest is infinity.

Therefore, you know that by dialling in 0.24m into your focus ring you will have everything from 0.19m to infinity in nice crisp focus.

Check also the DOFmaster website and their online DOF/hyperfocal calculator.

Happy days!!

Tobers

 

[Deleted member 152499]

Possible n00b moment coming up

Thanks Tobers, and whilst I managed to follow the majority of your instructions, I must admit I'm stumped by the one suggesting:

"Therefore, you know that by dialling in 0.24m into your focus ring you will have everything from 0.19m to infinity in nice crisp focus"

How do I (or perhaps more importantly, can I, with my kit lens) dial in said value on focus ring???

Apologies if I'm missing something really obvious.....

 

[jonnypb]

great capture, that method really does work

must blow the dust off my book and finish reading it. It seems the type of book that you'll keep reading again and again as you'll be picking up more and more info each time you read it

 

[allymac123]

seems to work pretty well. And a lovely pic to boot!

 

[Tobers]

How do I (or perhaps more importantly, can I, with my kit lens) dial in said value on focus ring???

The lens focus ring usually has a distance scale printed on it in feet and meters and a line of some sort to line it up on. Twiddle the focus ring until the required distance lines up with the line (or as near as you can get)

 

[Deleted member 152499]

The lens focus ring usually has a distance scale printed on it in feet and meters and a line of some sort to line it up on. Twiddle the focus ring until the required distance lines up with the line (or as near as you can get)

I think my poxy kit lens only comes with focal length indicators (IIRC, I can be corrected)...

 

[Deleted member 152499]

I think my poxy kit lens only comes with focal length indicators (IIRC, I can be corrected)...

This time with picture

 

[Tobers]

Ah! Time for a new lens then

http://www.canon.co.uk/Images/14_344285.jpg

You can see the focus distance thingy just above where it says "image stabilizer".

 

[Deleted member 152499]

Ah! Time for a new lens then

Sold!!

The Sigma 17-70mm edges ever nearer

 

[AceAceBaby]

Metering off blue sky does makesense- Isn't the sky a reflection of the overall light?

 

[Geordie Jester]

here is a comment about this topic

*****************************************
Exposure in this instance is the allotment of light energy delivered to the film or digital chip. Gross over or under exposure results in a spoiled picture. Somewhere in-between is a span that will yield an acceptable picture. This span dictates how tones will reproduce. As an example human skin can be reproduced too dark or to light. A skilled photographer can measure scene brightness with a light meter and adjust the camera setting to obtain a suitable skin tone. Such adjustments and setting are not limited solely to a skin tone. A skilled photographer can apply exposure control and exercise control over the rendering of memory colors (tones) such as snow, or sand, or water, or sky, or the like.

Logic would tell you that the center tone we call middle gray should be replicated by a surface with a 50% reflection. However, the human eye brain tends see in tone steps that are not equal. As a result an object with an 18% reflectance appears to us as middle gray. See the works of Albert H. Munsell.

As to exposure theory: If a scene in nature is exposed so that an 18% is rendered correctly, all other tones will be rendered correctly by law (law of reciprocity (Hurter & Driffield). This is true if the tones do not exceed the range of the film or chip (dynamic range). Now the
light meter is calibrated to properly render a gray card with a surface reflection of 18%.

Colored objects like oranges or sky or lemons, are identified first by hue (red, yellow, green, purple-blue and red-purple). Then by value or scale of reflectance i.e. dark, medium, light etc.

Now in this instance we are trying to render the sky correct as well as most all other tones. We know that if we had a gray card and a correctly calibrated meter we could measure the gray card, set our camera as indicated and voila a correct exposure results. In lieu of a gray card we hunt for a substitute. We can choose blue sky, not because it is blue but because its value (intensity) is about at the middle of the scale thus it can serve as a suitable substitute.

Alan Marcus
*******************************************

 

[danburbridge]

with reference to hyperfocal distances: buy old manual focus lenses

They almost always have a hyperfocal scale on them - ie they have indicators at the different f stops - so you adjust the focus until the infinity mark matches the corresponding F stop value you are using and you will have everything from infinity back to whatever the value at the close end is in focus.

Makes a lot more sense when you see one:

http://foto.recenzja.pl/obrazy/Flekt204/f2040_b.jpg

 

[richard plumb]

so does that take into account changes in brightness of the sky? does it have to be a clear sky or does it work on an overcast day?

I tried something similar which was to meter on some green grass, when taking some shots of my son's birthday party which had outdoor games. Set it up in manual exposure and then just forgot about it and started shooting.

Surprisingly relaxing knowing you don't need to mess about with the settings to make sure they aren't getting fooled by dark/light areas etc. (providing the lighting stays the same of course, which it was)

 

[stevegreen]

so does that take into account changes in brightness of the sky? does it have to be a clear sky or does it work on an overcast day?

I tried something similar which was to meter on some green grass, when taking some shots of my son's birthday party which had outdoor games. Set it up in manual exposure and then just forgot about it and started shooting.

It will only work on a clear blue sky as far as I know, metering off a cloudy sky will simply leave everything underexposed. As you say, grass is another option if the sky is cloudy and apparently concrete is good for a 18% white.

 

[danburbridge]

The back of your hand is normally not far off (provided you are white but not too pale).

It also has the benefit of being to hand at all times (boom boom)

 

[Geordie Jester]

so does that take into account changes in brightness of the sky? does it have to be a clear sky or does it work on an overcast day?

yeah I think they talk of the "deep blue" that you get in the sky with your back to the sun.

when the sky is pale, the result will be you end up underexposing.

I definately use manual mode more and more though. for one thing it is handy to use the focus lock on an object and not be metering at the same time. It is rare that I want to meter and focus on the same things

 

[Steve Zissou]

Weirdly enough, I finally got round to reading this book over the course of this week, fininshing yesterday (I have an electronic version of the book!) and I'm off out at the weekend to try some bits and pieces he suggests - including metering off the sky (IF it's blue of course!!!)

 

[Sicknote10]

From reading this topic I've decided I need to buy a book and a new kit lens... grr! (oh new hd tv, you must wait a bit longer!)

Blue skys have been hard to come by the last few months around here, hopefully will be able to try it out soon though, cheers