Month: August 2012

In my book there are two fundamentals to what makes a photo good or bad and they are proper focus and a perfect exposure. Get either of these things wrong and you’re fighting an up hill battle from the off.

In this post I’ll look at exposure compensation which allows you to override the camera’s suggested exposure and make your image lighter or darker as you require. Although the name may vary a bit, almost all cameras have this function. You’re looking for a button that has a half white, half black square and has the plus minus symbols… Basically something like the image on the right.

Why compensate?
In this modern age of digital everything you may be wondering why the cameras exposure wouldn’t be right all the time. By now some boffin must have figured out a way to get the perfect exposure, right? Well that’s nearly right and every new camera that comes out gets better and better at nailing the exposure but there are two problems. Firstly all metering systems start with the theory that the world (on average) is a mid grey, That’s great most of the time except for the times when it’s not, like when photographing snow or someone wearing black.

  
The white shell in the centre of the frame has caused a small amount of under exposure.
Dial in +1 stop of exposure compensation and the exposure is correct.

The second problem is exposure is often open to interpretation. A scene where the exposure is biased to highlights will look very different to one where it’s biased to the shadows.

Compensation in action
If you move the exposure compensation to the left you’re adding negative exposure and your photo will be darker. This is great when photographing dark subjects or when you want to capture highlight detail.

Moving exposure compensation to the right makes your photo’s brighter, perfect for photographing light things like snow, sandy beaches and backlit scenes.

Click on an image to enlarge

When in doubt try taking the photo at a couple of different exposures but always remember once you’re done with exposure compensation reset it to zero.

Fix it in Photoshop
I love Photoshop but fixing exposure in Photoshop isn’t a long term plan you should stick with. Yes I know the RAW format gives you latitude of exposure you don’t get in JPG but adjusting exposure AFTER you’re taken the image will slow your workflow down and degrade the image. Both of these things may be slight but they add up. More over getting the image right in camera helps you to see the photographs not just take them.

The other day whilst I was running a lighting training session one of my students filled up his memory card. Fortunately he’d packed an older spare card so we swapped to that and carried on shooting.

So what’s so unusual about that you may ask. Well, nothing. But what happened next got me thinking.

He was shooting in RAW+JPG and when we inserted his memory card into my card reader the JPG’s opened fine but every RAW file was corrupted. How could this be? Put simply the memory card couldn’t keep up with the RAW data and the images corrupted.

The need for speed
So how fast a memory card do you need? Well if you’ve using a modern DSLR camera and shooting RAW then there’s a lot data to move. Although pretty much any card from a respectable brand will work just fine, using a faster card means less buffering time and quicker file transfers to your computer.

As a very rough guide a RAW image is a bit over 1MB per million pixels, so something like my Canon 5D Mk2, which has 22 million pixels, will produce a 25MB file for each RAW image.

X-Speed vs MB/S 
When buying memory cards you’ll find their speed is listed in one of two ways. It’ll be either Megabytes Per Second (e.g. 30 MB/S) or X speed ratings (e.g. 100X). This throws up a bit of confusion, which is faster.

Fortunately there is a formula for converting X speeds to MB/S.

One speed is 150 Kilobytes per second (KB/S), so a 100x speed memory card is 15000KB/S or the same speed as a 15MB/S memory card.

So if maths isn’t your strong point you may find this table helpful when comparing cards.

It’s worth noting that memory card speeds relate to their write speed not their read speed. Read speeds are often different and usually faster then the write speeds.

Faster isn’t always better
It’s worth noting that simply having a faster card doesn’t mean it will work faster. Camera’s, card readers and computers will all play their part when it comes to speed. If your device isn’t able to work at the fastest speed your card offers, you won’t see the benefit. A prime example of that is using a high speed card in a USB2 card reader.

I know, I know! It’s far too long since the last photo challenge and my inbox has been filling up with question like, “What’s the topic for the next photo challenge?” and “When will the next photo challenge be starting?” Well the good news is it starts right now, the bad news is you have less then two weeks to get your entry in.

For the August photo challenge your theme is…

Beach or Sea

How you decide to interpret that theme is entirely up to you. Perhaps you’ll want to take it literally and enter a photo of a some pebbles, a sand castle or people enjoying being at the coast. Maybe you’ll try something a little more abstract like looking for sand patterns or a long exposure to smooth out the waves.

Once you’ve made your photo you’ll then need to do three things…

1. Check your entry meets with the rules at the bottom of this post.
2. Upload your image to the Flickr Group page at http://www.flickr.com/groups/2025164@N25/

I’m very happy to report that the Photo Challenge is once again being sponsored by Print Yours. They are an independent print lab who specialise in creating small run, high quality prints. Check out their web site for more information http://www.printyours.co.uk/

So what will the winner receive? Well, Print Yours have generously offered to print the winning entry on their 270gsm Photo Satin paper up to a whopping 24”x16”. That’s an £18 print for FREE! If you’re the lucky winner then all you need to do is send a high res version to Print Yours (via email) and they’ll do the rest.

RULES
One entry per person
Entries must be uploaded to the correct Flickr group by 3rd September 2012
Entrants agree to the use of their image on the Gavtrain webpage / facebook page solely for the purpose of announcing the results
The image (including any manipulation or added elements) must be the sole work of the entrant
The winner will be selected by Gavin Hoey and his decision will be final
No alternative prizes are available
Only the winning picture will be printed
The winner will be notified by Flickr direct message.
The winner will be required to email a high res (printable) version of the winning image to Print Yours by
30th September 2012
The winner will be announced on the Gavtrain Facebook Page during September 2012

Good Luck