12MP is enough (or was that 640k?)

del.icio.us Tags: Olympus,DSLR,FourThirds

Image via Wikipedia

The forums at DPR are going a bit ga-ga over the CNET PMA interview with Akira Watanabe, manager of the SLR planning department. He said - "We have no intention to compete in the megapixel wars for E-System".

It is quite common in conversations with self appointed gurus, to moan about how the small sensors in cameras keep being pushed into higher Megapixels whenever a new model is released. These people say that manufacturers of cameras should voluntarily step back from the Megapixel race. And now, when one manufacturer says so, the same people or other doomsayers step forward and say that staying at a plateau of 12MP for the Four Thirds sensor signifies the beginning of the end.

What people choose to skip, is the following remark by Watanabe-san - “Instead, Olympus will focus on other characteristics such as dynamic range, color reproduction, and a better ISO range for low-light shooting”.

It is also well espoused by reviewers and by the anti-Four Thirds opinionists, that the weak points in the Four Thirds cameras is about a stop of dynamic range and earlier onset of digital image noise (graniness). So Watanabe-san is simply stating that the company does recognise the challenges in this sensor size and they want to improve the performance of these aspects on a higher priority.

Certainly, if Panasonic (or less likely, Kodak) comes to the table and brings an even denser Megapixel sensor, it would not be logical to sweep such a gift into the rubbish bin.

Much is also made of Watanabe-san’s statement: "We don't think 20 megapixels is necessary for everybody. If a customer wants more than 20 megapixels, he should go to the full-frame models”.

Again, nothing surprising in that. Lots of people don’t need the 20MP. Look at the long sales life and service life of the redoubtable Nikon D40 – a 6MP camera. And routinely still recommended as a useful camera – with punchy colours, low image noise. Many people, including myself, seldom print now (again there are aged, veteran photographers who frown on this and insist that the object of photography IS PRINTING) – and certainly web images or screen images, as a output result, uses less than 2MP.

So, why the angst? Why the neurotic chest thumping? It’s because someone practical and pragmatic stood up and announced that there is a finite limit to real sensors and real optics and the Four Thirds design as at the time of the interview.

Will there be electronic and optical improvements? Sure. By how much and how soon?

Should aspiring pros and pro-like fans abandon Four Thirds as of now so that they can fill their bag with CaNikZeiss lenses? Maybe. If you must have the huge Megapixel, the wafer thin DOF, the super creamy bokeh that an 85mm f/1.2 lens will deliver, the ISO 2500 without digital image noise, then they should have left the station like, oh, a year ago.

For the rest of us, the practical niceties of the Four Thirds system daily proves it’s worth. And when the time comes, when the legendary 24x36mm “full frame” sensor DSLR sells at today’s entry level price, we’ll take our options then. Until then, Carpe Diem – don’t burden yourself with the perceived loss of assets that aren’t.

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What is Correct Exposure Part 2

del.icio.us Tags: exposure,dof,shutterspeed,f/no,photography

The Perfect Picture’s Creatively Correct Exposure video tutorial is interesting to watch, but it encourages newbies to link two different facets, “technically correct exposure” and “creative choice of f/no for depth of field” without a seam. Sure, a veteran photographer juggles both these facets intuitively.

The newbie though, does need to pause and think that these are two facets – they overlap in the fact that the f/no is present in both facets but that’s the only thing they overlap in. Otherwise the spiral of confusion, that winds into equivalence of every facet (f/no, shutter speed, ISO, sensor size, focal length) perpetuates.

In truth, Bryan is demonstrating exposure (the permutations of shutter speed and f/no). He’s not speaking of twiddling the ISO dial (because in the film days, you could not easily change ISO in mid roll) nor is he talking about the effect of different digital sensor sizes and focal length.

Bryan Peterson explains this slightly better in this second video – emphasising choice of shutter speed:

and another video, emphasising f/no

In truth, Bryan's videos and the title of this very blog post should be more aptly changed to "Choosing an aperture and shutter speed permutation to effect creative control of the visual aspects of the photo" rather than "Understanding Creative Correct Exposure". Because we have not yet begun to discuss whether we should underexpose or overexpose a scene (in modern parlance on a digital camera, twiddling the Exposure Value compensation dial, to creatively darken or lighten the whole photo so that we can target the face of a person as the most important element in the photo.

Insights and Teach Ins

Image by Dr Craig via Flickr

I read Chuck Gardner’s Zone System articles some time back and it was one of those epiphany days. He writes well, one of my latest reads is his Colour Management article. Worth spending the time to read, even sacrificing a few trees,

More Depth of Field Teach Ins

Seems the first topic that newbie photographers need to learn is Exposure. The second is Depth of Field. So a lot is written and experts expound theories and DOF calculators abound. But newbies still don't grok it immediately. How about some YouTube?

Mastering the UWA

Image via WikipediaOlympus has now released the 9-18mm Ultra Wide Angle (UWA) lens for the Four Thirds DSLR mount. People who have been yearning for a 7-14mm Zuiko Digital (high priced, sharp, big, bulging front element, no front lens thread) now have a affordable option. An UWA is not for everyone though and early buyers are also cautious of the lens quality. So, they're grappling with two issues - is the lens good and secondly, how do you actually use this lens well.

I came across Petteri Sulonen's article - Mastering Wide Angle. That woke me up a bit.

• If your camera is even slightly out of the horizontal, verticals will converge
• "Short focal lengths have lots and lots of depth of field." They sure do. However, the other side of the coin is that the attendant wide scenes tend to be very deep, so you're going to need all of it, and more, if you want to keep everything sharp - The trouble is that while there's lots of DOF, the scenes are very deep, and wide-angle scenes tend to draw the eye to "wander" around the frame, which means it'll eventually land on something that's not critically sharp. A second complication is that auto-focus really doesn't work that well with wide-angle. Especially with the shorter, darker lenses hyperfocal distance wide-open is really quite close. Moreover, objects even a few meters away may be quite small in the frame, while the AF sensors are quite large. This means that AF will have real trouble latching onto anything more than a few meters away.
• you as the photographer have to take flare into consideration anyway; either work it into the composition or try to minimize it while composing.
• Expose for maximal dynamic range, then correct in post-processing.

On focussing, he says:

• Stop down as far as you can.Identify the visual center, and focus on that.
• If you want infinity to be sharp, focus on infinity.
• If you have to choose, focus behind rather than in front of the subject.

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• Depth of field: The small-sensor difference

Explaining Depth of Field

Whenever you read some material on Depth of Field and the related aspects of photography, Circle of Confusion, Aperture Size, f/number, Lens Focal Length and Sensor Size, it goes ok for a few paragraphs and suddenly you have this MEGO phenomenon take over. As more senior photographers try to explain this DOF to newbies, things soon get worse.

If you can handle the equations and tables, then the following resources are good:

• Wikipedia: Depth of Field
• DOF Master: Depth of Field Calculator - also has links to interactive programs for Windows, PalmOS, iPhone, iTouch, web based tables.
• Freeware DOF Calculator for PocketPC
• Olympus Europe's hosted DOF Calculator (Pocket PC)
• Justin Snodgrass has a video called Depth of Field Explained. It's not bad - it's a video so you can pause, rewind and repeat.
• Photozone: Depth Of Field Calculator (Java applet)
• Has a simple visual comparison of DOF at f/2.8, f/5.6, f/11.
• Has a Java applet showing DOF and visual chart. You key in focal length, focussing distance, CoC

The depth-of-field is dependent on the OBJECT MAGNIFICATION ON THE FILM and the chosen aperture at a specific focal length.

Focal length affects perspective. See Photozone visual comparing 17mm, 35mm, 50mm, 100mm. Also read this discussion by P.A. van Walree

Photozone DOF Confusion:

COC [Circle of Confusion] is not a function of format.

“But wait a minute,” you say, “why do some applets use format instead of sharpness?” These applets assume that in photography the subject will be framed the same regardless of format. In other words, to frame the subject from the same distance the larger format will need a longer focal length lens, or the smaller format will need to be moved further away from the subject (or vice-versa).

Photozone DOF Preview has an interactive visual of how pressing the DOF preview looks like when your shooting aperture is less than you viewing aperture.

DOF in the context of different digital sensor sizes

DOF is not difficult to explain for one camera. It gets more complicated to explain when you compare a 35mm film camera against say a Four Thirds Sensor camera.

1. For the same optical focal length lens on two different cameras, the lenses don't have a different DOF. The DOF is the same.
2. Take a 100mm lens that would fit a 35mm film camera. Fit it on a film camera and then fit it on an Four Thirds Sensor camera. If the lens fits either, you still have a 100mm lens. Assume both cameras can shoot with the lens.
3. But because the Four Thirds sensor is 2x smaller, it only sees half the image. That's why they call it a Crop Factor. Say you can see a face occupying the full frame on the film camera. With the Four Thirds sensor sensor, being smaller, you can only see the fellow's hair and eyes.
4. What this means is you appear to be "closer" to the person even though you are standing at the same distance, same lens. But your camera is different. At this point, the DOF is the same.
5. So, what happens? In order to get the full face into the picture, you have to use your legs and walk backwards.
6. Now that you have walked backwards from the subject, you are not comparing apples to apples anymore. You are comparing the Four Thirds Sensor camera, standing further back vs the film camera standing nearer to the subject. You have changed your camera to subject distance.
7. DOF is based on distance between you to the subject. So, yes, in this case the Four Thirds Sensor camera, appears to have a deeper DOF compared to the film camera. Not because the lens is different, not because the camera sensor size is different, but because you used your legs to walk back and you changed the distance to the subject.

Updated 11th October 2008: Tamron visual simulation of DOF effects

Sometimes, you take the other tack and just say - heck, here is a camera, let's go out and shoot and see.

(Photo was shot using 250mm f/5.6 CAT lens mounted on a FourThirds sensor camera - Olympus E-510)

(Photo was shot using 250mm f/5.6 CAT lens mounted on a FourThirds sensor camera - Olympus E-510)

del.icio.us Tags: DOF,Photography,Reference