Lens question
Author
Discussion

curtisl

Original Poster:

1,406 posts

236 months

Tuesday 15th April 2008
quotequote all
Excuse my ignorence but this has been something that has been bugging me.

I have two lenses for my canon, one is 18-55mm and the other is 28-90mm. what does each one do better?

ehasler

8,579 posts

313 months

Tuesday 15th April 2008
quotequote all
curtisl said:
Excuse my ignorence but this has been something that has been bugging me.

I have two lenses for my canon, one is 18-55mm and the other is 28-90mm. what does each one do better?
The numbers relate to the focal length of the lens, with a smaller number meaning a wider field of view.

The 18-55mm lens will enable you to fit more in the frame at the 18mm end than the other lens, while the 90mm end of the other lens will enable you to zoom in more to the scene.

Also, there will be another number on the lens after the focal length, which will be the aperture (e.g., f4). This tells you the maximum size of the hole that lets in the light (smaller number = bigger hole), and generally speaking, the smaller the f number, the better the lens.

Piers_K

234 posts

225 months

Tuesday 15th April 2008
quotequote all
Assuming the 18-55 is an EF-s kit lens and the 28-90 is a normal film EF kit lens.. they are virtually the same focal length..

18-55 x 1.6= 28.8-88...

Doubt there will be much difference in picture quality either if the above is correct...

Road2Ruin

6,525 posts

246 months

Tuesday 15th April 2008
quotequote all
ehasler said:
curtisl said:
Excuse my ignorence but this has been something that has been bugging me.

I have two lenses for my canon, one is 18-55mm and the other is 28-90mm. what does each one do better?
The numbers relate to the focal length of the lens, with a smaller number meaning a wider field of view.

The 18-55mm lens will enable you to fit more in the frame at the 18mm end than the other lens, while the 90mm end of the other lens will enable you to zoom in more to the scene.

Also, there will be another number on the lens after the focal length, which will be the aperture (e.g., f4). This tells you the maximum size of the hole that lets in the light (smaller number = bigger hole), and generally speaking, the smaller the f number, the better the lens.
Gets even more complicated when you compare digital SLRs with non digital as most of them have some lense multiplying effect on the focal length.

ehasler

8,579 posts

313 months

Tuesday 15th April 2008
quotequote all
Piers_K said:
Assuming the 18-55 is an EF-s kit lens and the 28-90 is a normal film EF kit lens.. they are virtually the same focal length..

18-55 x 1.6= 28.8-88...

Doubt there will be much difference in picture quality either if the above is correct...
The focal length is listed as 35mm equivalent though, so if you fit both of the above lenses to the same camera, they will both have the crop factor applied to the focal lengths.

So 18-55 x 1.6 = 28.8-88
28-90 x 1.6 = 44.8-144

curtisl

Original Poster:

1,406 posts

236 months

Tuesday 15th April 2008
quotequote all
ehasler said:
curtisl said:
Excuse my ignorence but this has been something that has been bugging me.

I have two lenses for my canon, one is 18-55mm and the other is 28-90mm. what does each one do better?
The numbers relate to the focal length of the lens, with a smaller number meaning a wider field of view.

The 18-55mm lens will enable you to fit more in the frame at the 18mm end than the other lens, while the 90mm end of the other lens will enable you to zoom in more to the scene.

Also, there will be another number on the lens after the focal length, which will be the aperture (e.g., f4). This tells you the maximum size of the hole that lets in the light (smaller number = bigger hole), and generally speaking, the smaller the f number, the better the lens.
Cheers, the other lens (EF 28-90mm f/4.0-5.6 II) is off an older eos 3000v which i was looking to sell but i may just keep hold of it just for the lens.

Out of interest does anyone know what the going rate would be for the Canon 3000v with the EF 28-90mm f/4.0-5.6 II Lens Kit, is there still a market for non digital cameras.

ThatPhilBrettGuy

11,810 posts

270 months

Tuesday 15th April 2008
quotequote all
curtisl said:
Out of interest does anyone know what the going rate would be for the Canon 3000v with the EF 28-90mm f/4.0-5.6 II Lens Kit, is there still a market for non digital cameras.
eBay shows the odd body only going for between £5 and about £30, with new kits around £70. All boxed etc I'd say you'd be lucky to get £40 - £50.

leightonjames

1,346 posts

245 months

Tuesday 15th April 2008
quotequote all
Whilst we are on the topic, what on earth is 18mm or 90mm is it the length of the lens or!?

Cheers smile

ThatPhilBrettGuy

11,810 posts

270 months

Tuesday 15th April 2008
quotequote all
leightonjames said:
Whilst we are on the topic, what on earth is 18mm or 90mm is it the length of the lens or!?

Cheers smile
http://en.wikipedia.org/wiki/Focal_length

ehasler

8,579 posts

313 months

Tuesday 15th April 2008
quotequote all
leightonjames said:
Whilst we are on the topic, what on earth is 18mm or 90mm is it the length of the lens or!?

Cheers smile
It's directly related to the size of the photographer's manhood, which is why guys are so keen to boast about their new 400mm lens wink

A good explanation is here

http://www.dpreview.com/learn/?/key=focal+length

curtisl

Original Poster:

1,406 posts

236 months

Tuesday 15th April 2008
quotequote all

[/quote]

So 18-55 x 1.6 = 28.8-88
28-90 x 1.6 = 44.8-144
[/quote]

So the questions continue, what is the multipler of 1.6 and what does that equate to?

ehasler

8,579 posts

313 months

Tuesday 15th April 2008
quotequote all
curtisl said:
So the questions continue, what is the multipler of 1.6 and what does that equate to?
35mm film cameras used film with a size of 36x24mm. Most digital SLRs have a sensor size smaller than this, so if you imagine the lens beaming an image onto a 36x24mm piece of film, then you put your 22.2 x 14.8mm sensor (Canon 40D) over this, it will only record part of the overall image. The image you end up with appears similar to what you would get with a longer lens on the 35mm film camera, so to convert this, you use the crop factor number given by the camera maker.

So, a Canon 40D with a 22.2 x 14.8mm sensor and 100mm lens will record the same image as a 35mm film (or full frame DSLR) camera with a 160mm (100x1.6) lens.

Again, wiki is your friend for a more detailed explanation smile

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

Edited by ehasler on Tuesday 15th April 15:38

flat-planedCrank

3,697 posts

233 months

Tuesday 15th April 2008
quotequote all
Just to re-state..
The crop-factor of your camera applies to all lenses, irrespective if they are EF, EF-S, kit lenses, or any other 'digital only' lenses made by other manufacturers.

I.e. An EF 100mm, EF-S 100mm, and 100mm 'digital only' lens (made by another 3rd party manufacturer) would all be equivalent to a 160mm lens on an 'old' film slr / full-frame dslr.



(The only difference between EF / EF-S lenses is that you cannot mount EF-S lenses on full-frame dslr's (5D / 1Ds series)).


Cheers.

Piers_K

234 posts

225 months

Tuesday 15th April 2008
quotequote all
Note to self.. engage brain fully before posting... getmecoat