Field of View Question - 37mm vs 28mm?

Grainbelt

I have a Canon S5 IS. Great fun, takes far better pics than my old Olympus D600. I'm developing some proficiency with the manual controls, and will be picking up a flash shortly, probably a 430EX.

My question is this: the S5IS has a 37mm (equivalent) lens. There is an accessory wide-angle converter, .75x. Apparently that is about 28mm.

Any functional advantage? I shoot a lot of landscapes, generally when I'm out and about on the bike and capturing the scenery along the way. I understand that I would just be pouring more light onto the relatively small sensor...

Anything else I'm missing?

Also, I want the bayonet adapter and lens hood. We get some harsh sun light around here...

wxwax

I put the wide angle attachment on my G3 and enjoyed it. I'm not sure about landscapes, though. I got a lot of barrel distortion.

Grainbelt

wxwax wrote:

I'm not sure about landscapes, though. I got a lot of barrel distortion.

Do you mind explaining?

sirsloop

Barrel distortion is an effect where lines in a photo are bent... so if you took a photo of a brick wall the bricks would look like they are warped.

here...

http://en.wikipedia.org/wiki/Barrel_distortion

Point and Shoots typically experience this because the lenses are made on the cheap and are super compact.

Grainbelt

Thx much. I may get one to play around with, and learn more about barrell distortion, apparently.

claudermilk

Did you see this thread? http://www.dgrin.com/showthread.php?t=73551

A couple of online tools to see the differnece between various FOVs and focal lengths. Note, you are not necessarily putting more light on the sensor, just changing the magnification and angle of view. For example a shutter speed of 1/100 @ f8 on a 28mm lens lets in the exact same amount of light as 1/100 @ f8 on a 280mm lens--you're just 10x more magnified and the angle of view is much narrower.

Grainbelt

claudermilk wrote:

Did you see this thread? http://www.dgrin.com/showthread.php?t=73551

A couple of online tools to see the differnece between various FOVs and focal lengths. Note, you are not necessarily putting more light on the sensor, just changing the magnification and angle of view. For example a shutter speed of 1/100 @ f8 on a 28mm lens lets in the exact same amount of light as 1/100 @ f8 on a 280mm lens--you're just 10x more magnified and the angle of view is much narrower.

I did see the thread, and played with that field of view tool a bit. It has some good tools if you have an SLR or know what the 'crop' of your sensor is. The S5 IS is 1/2.5 sensor, would that be 1:2?

Agree on the light/sensor topic, I'm really attempting to put more detail on the sensor, not more light.

claudermilk

Yeah, a 2x crop would be the closest in that tool. It's aimed at DSLRs, not P&S, so the crop factor doesn't cut down as much--but then the P&S tend to have really, really wide lenses to compensate. Case in point, your lens is a 6-72mm. How many 6mm lenses have you seen for DSLRs? So, at 2.5x look in the 15-180mm range set to FF on that tool to see what your camera can do. Well, ok 17mm at widest, so you can get slightly more of the scene than shown.

Grainbelt

claudermilk wrote:

Yeah, a 2x crop would be the closest in that tool. It's aimed at DSLRs, not P&S, so the crop factor doesn't cut down as much--but then the P&S tend to have really, really wide lenses to compensate. Case in point, your lens is a 6-72mm. How many 6mm lenses have you seen for DSLRs? So, at 2.5x look in the 15-180mm range set to FF on that tool to see what your camera can do. Well, ok 17mm at widest, so you can get slightly more of the scene than shown.

The 6-72 is a claimed 36-430ish 'equivalent'. Does that mean full-frame equivalent?

sirsloop

Lenses behave differently on differnt sized sensors. So lets saw you have a point and shoot and a canon 5D (full frame). If you set your point and shoot to 6mm, you would need to dial in 36mm worth of zoom on the 5D to get the same picture. The same holds true for any camera that's not full frame. Example... a 40D (1.6x sensor size factor... so smaller) with a 300mm lens attached to is the same amount of zoom as a 5D (full frame) with a 480mm lens on it. If you look at other systems like Olympus 4/3rds... that has a 2x size factor so lenses like their 55-200 really are like putting a 110-400 on a full frame body. Its just a way to benchmark the amount of zoom a camera has. Because different zooms works differently on different , there has to be some way to compare their field of view.

claudermilk

Grainbelt wrote:

The 6-72 is a claimed 36-430ish 'equivalent'. Does that mean full-frame equivalent?

Yes. All the equivalency calculations are getting back to the old, familiar 24x36mm film frame.

jeffa

claudermilk wrote:

Yes. All the equivalency calculations are getting back to the old, familiar 24x36mm film frame.

For focal length comparison purposes the crop is not relavant.

i.e. as the sensor size stays the same the area viewed is 1/4 if the focal length is doubled.

check out the tool for confirmation
http://lens-reviews.com/Technical-Talk/Technical-Talk/Lens-Field-of-View-Visualisation-Tool.html

claudermilk

I'm not quite sure I follow your point. Let's see if I got it.

True focal length never changes. A 50mm lens is always a 50mm lens. THe perspective you get from it remains constant regardless of the sensor size you put behind it. However, the Field of View does change; for example on the typical Canon crop sensors, the 50mm lens is the same FOV as an 82mm lens. As shown in the nifty comparison tool.

So, my answer to the last question is valid. The 6mm lens on the P&S in question is similar to the FOV of a 36mm lens on a 24x36mm sensor.

Really, the confusion on equivalency is perspective vs angle of view.