Archive for April, 2010

Wednesday, April 28th 2010

Automatic Lens Correction in Lightroom 3

The one major feature that I have always missed in Lightroom is now being added! Me and about a zillion other Lightroomists have been waiting (and asking) for this for ages.

Now Adobe have announced that this will be in the final version of Lightroom 3.

So what is it? Automatic Lens Correction based on lens profiles. It lets you deal with the three main optical flaws of a lens in just a single click!

Here’s Adobe’s video showing off the feature in Adobe Camera Raw 6:

Exactly how it will work in Lightroom 3 remains to be seen, but I’m sure we’ll see the same sliders. The question is how Lightroom will handle local adjustments (spot cloning or dodging/burning) when the image is warped by the lens correction feature.

When Adobe released Lightroom 3 beta 2 without this feature, I was convinced we wouldn’t see it until version 4, at the earliest. So, three cheers for the Adobe Lightroom developers!

Wednesday, April 28th 2010

The Myth of the Megapixel Myth

When Canon released the 50D I thought it had too many pixels. And I thought I was smart in thinking so.

Canon, please understand that SLR buyers aren’t as gullible as compact buyers when it comes to megapixels.

But in reality I had fallen for the myth of the megapixel myth.

(This post grew to almost a 1,000 words. If you haven’t got all day, skip to the conclusion.)

Lets start from the beginning.

The megapixel myth refers to the notion that a higher number of megapixels equals a better camera. And in calling it a myth, we are implying that camera manufacturers are increasing the number of megapixels on camera sensors only to trick everyone into constantly upgrading their cameras. Indirectly, we are implying that there is some intermediate number of megapixels that should be considered optimum for a given sensor size.

Ironically, the optimum number of megapixels always seems to be equal to the number in the camera generation one step back from the very latest release. Giving thousands and thousands of spoilt (and misguided) photographer brats an excuse to pour out their disgust in a million forum posts. A bit like I did.

One day it won’t make sense to add more pixels, but we have a long way to go until we reach those numbers. As it is now, we’re still gaining a lot of detail in our photos when the resolution increases.

On photography discussion forums you often hear the claim that a high resolution sensor needs really good glass, or even that it outresolves available lenses.

But those claims simply aren’t true. They are based on an incorrect mental model of how resolution works.

Even if you’re using a really cheap or soft lens, you’ll still get more detail out of it with a higher resolution sensor.

Have a look at these two tests at Photozone.de:

(If you own the 18-55mm IS, don’t scream at me – I’m not claiming it is a soft lens. Read on.)

Scroll down to the section titled MTF. The diagrams show how much detail the lenses can produce on the two cameras. Specifically, they show how many horizontal black and white lines you can fit into the image height before they blend together into a grey mush.

Note that the Extreme Corners which are the softest areas of the lens, produce a higher level of detail on the 15 megapixel camera – just like the centre of the lens. So just because they’re soft on the 8 megapixel camera doesn’t mean they won’t produce more detail on a 15 megapixel camera. This is because the lens and the sensor both combine to produce the details in the final image.

A sharper lens will always give you finer image detail, no matter what the sensor resolution. And a higher resolution sensor will always give you finer image detail, no matter what the lens in front of it!

Some maths

Mathematically, this is an approximation of how it works:

1/I2 = 1/L2 + 1/S2

or

I2 = 1 / (1/L2 + 1/S2)

I is image detail, L is lens resolution and S is sensor resolution. These are linear resolutions, just as in the MTF-charts I referred to above. (Megapixels are two linear resolutions multiplied together, width x height.)

Let’s say we have a camera with S = 2,300 and a lens with L = 3,000. That would give us an image with 1,825 lines per picture height:

I2 = 1 / (1/3,0002 + 1/2,3002) = 1,8252

I = 1,825

If we now buy a better camera with, say, S = 3,200 we’ll get more and finer details in our images:

I2 = 1 / (1/3,0002 + 1/3,2002) = 2,1872

I = 2,187

As you can see, the lens is still able to resolve a lot more detail than we get in the final image.

To get anywhere near the maximum performance out of a lens, the sensor needs to resolve at least three times as much as the lens:

I2 = 1 / (1/3,0002 + 1/9,0002) = 2,8462

I = 2,846

2,846 lines is basically 95% of what the lens in this example can resolve.

As you may have noticed, the numbers in my examples above are not just taken out of the blue. The values for the sensor resolutions correspond to the image heights in pixels of the Canon EOS 350D and Canon EOS 50D.

I chose a lens resolution value that would make the image resolution values (1,825 and 2,187) correspond fairly closely to the average measured resolution in Photozone’s tests that I linked to. In other words, 3,000 line widths (per image height) is probably roughly what the 18-55mm IS can resolve.

Conclusion

So, what does this all mean? Well, since the numbers in the examples above correspond roughly to reality, we can make a simple calculation.

To get 95% of the resolution out of the Canon EF-S 18-55mm IS, or any other half decent lens, we need a sensor ~9,000 pixels high. Which means the width would be 13,500 pixels.

That equals 121.5 megapixels!

Even if we settle for 90% of the lens’ resolution, we need 60 megapixels to get there! Currently, Canon’s cameras are getting something like 60-75% out of the EF-S 18-55mm IS.

These figures obviously sound insane. But it is no more insane than having 12-14 megapixels in a compact camera. (A digital SLR has more than ten times the sensor area of a compact.) Flash memory and hard drives are getting cheaper all the time, so one day it will happen.

In other words, the megapixel myth is a myth in itself. Camera makers are not being tricksy when they add more megapixels. In fact, if we want to get the most out of our lenses we need lots and lots of megapixels!

Of course, there are many other aspects of a camera that are at least as important as the sensor resolution. And when it comes to compact cameras, with sensors no more than 5 or 6 mm wide, we’re probably reaching the upper limits of what makes sense. By now, I’m guessing that compacts are getting practically all the resolution out of their lenses.

Sunday, April 25th 2010

An odd collection of photos

I took a nice long walk yesterday in the Sundbyholm nature reserve. I was hoping to see some kind of wildlife. And I did see a woodpecker, but that was about as wild as it got. Still, I got a few other shots that I consider reasonably interesting.

Backlit trees along the road to Sundbyholms slott.

The road leading up to Sundbyholm looks good in almost any kind of weather or light, thanks to the rows of trees along it. The above photo was shot with my Sigma 10-20mm @ 10 mm.

Rose petals on the steps to Sundbyholms slott.

There was a wedding party at the Sundbyholm mansion. (The Swedish name Sundbyholms slott suggests it’s a castle, but that gives completely the wrong impression in English. This building is definitely more like a mansion.) All the guests had gone inside and the steps up to the front door were covered with petals. Taken with the Canon EF 70-300mm IS @ 75 mm, f/4.

Here are two other photos I got during the week.

27500 - 2010-04-23 kl 09.28

Here I used my Canon EF 70-300mm IS with a close-up lens attached to the front. This combination works quite well if you avoid using the very longest focal lengths. This was shot at 160 mm.

27477 - 2010-04-23 kl 09.16

Jenny had left a glass of water in the kitchen and the oxygen was beginning to settle in bubbles, as it tends to do. Canon EF-S 17-55mm IS @ 55 mm and f/4.

Sunday, April 25th 2010

Eskilstuna panorama – again

Was driving home through Eskilstuna centre yesterday and caught sight of this scene lit by the evening sun. Just had to stop and have another go at a panorama.

Panorama of buildings by the Eskilstuna river, Eskilstunaån.

Seven vertical shots, all at 1/125 sec, f/8 and ISO 200. I could have done this with only six shots though, since I’ve cropped both the ends off.

The full size image could make a 125×50 cm print @ 180 dpi.

Friday, April 16th 2010

Drag and Drop Attachments in Gmail

This is really cool.

The Gmail team have implemented drag ‘n’ drop for attachments, if you’re using Firefox 3.6 or Chrome.

I gave it a try and it works beautifully! This is the first real implementation of Firefox’s drag and drop support that I know of.

Friday, April 16th 2010

Back to Basics

Went out for a photo hunt on my bike today. Didn’t find anything interesting. Until I got back to our garden, where I found some very un-pretentious crocuses popping out of the ground.

I did see them on my way out, but thought naw, too boring. On the way back I thought, why not?.

I decided to use my 50mm and my angle-finder to get really low, to make them at least a bit different from the millions and millions of crocus photos flooding Flickr as we speak.

27310 - 2010-04-15 kl 12.5127305 - 2010-04-15 kl 12.4827313 - 2010-04-15 kl 12.5327309 - 2010-04-15 kl 12.5027327 - 2010-04-15 kl 12.58Yaaaawwwwn!

I don’t know, maybe I went overboard with the processing. What do you think?

The bumble bee in the last shot looks like he’s stretching, doesn’t he? And if you flip between these two photos quickly, it looks like he’s doing his morning exercises.

Friday, April 9th 2010

Wonderful Flickr Error Message

While updating one of my panoramas (replacing an existing image) on Flickr, I got this amazingly nonsensical error message:

Flickr Error Message

Is the file size limit 10 TB? Was I uploading an image larger than 10 TB? Waddya mean MB for pro users?

Thankfully I already knew the file size limit is 20 MB, so I could just ignore the stupid message.

Here’s what I believe the error message was trying to say:

File was too large – the limit is 10 485 760 bytes (20 MB for pro users).

I still can’t figure out why they would ever specify 10 MB in bytes though?!

Friday, April 9th 2010

Panoramas of Eskilstuna

Well, the title is perhaps a little misleading. Panoramas in or from Eskilstuna might be more correct.

I was inspired a few days ago by a blog post I saw somewhere … I can’t find it now though. Someone who had shot a panorama of Gamla Staden in Eskilstuna. So I decided to try the same thing.

Today was rainy, but then suddenly the clouds broke. Just before sundown, so the timing was perfect. I dropped everything and grabbed my camera bag.

Here’s what I came home with … Nothing spectacular really, but I had fun all the same. Click for larger 1800px versions.

Panorama of Norr, Eskilstuna and Eskilstunaån.

Norr.

Panorama of Gamla staden, Eskilstuna and Eskilstunaån.

Gamla Staden.

Panorama of Klosters kyrka and Stadsparken, Eskilstuna and Eskilstunaån.

Klosters kyrka.

Panorama of Strömsholmen, Eskilstuna and Eskilstunaån.

Strömsholmen.

Friday, April 9th 2010

Five Old Favourites

Looking through your old photos is always good fun. Here are five of mine that I really like, that I found while leafing through all my sets on Flickr.

Fors kyrka i dimma, Eskilstuna

Fors kyrka in Eskilstuna. Shot with my Sigma 10-20mm f/4-5.6.

14952 - 2008-04-23 kl 05.29

Faktoriholmen, Eskilstuna. Shot with my Sigma 17-70mm f/2.8-4.5. At 5.30 in the morning. Don’t think it was on the way to work – if I remember correctly I just woke up very early and felt very inspired.

Toadstool in Kronskogen, Eskilstuna.

A toadstool that I found in Kronskogen, Eskilstuna. Shot with my 50mm @ f/2. Added a slight split toning in Lightroom.

14879 - 2008-04-16 kl 19.39

Here I was playing about with various fruit and vegetables. This was shot with my 50mm @ f/2.8. Lit by nothing more than my desk light.

14781 - 2008-04-13 kl 21.30

Again, playing. This time with matches.