Crop factor and related issues and questions.

[jmorgan]

OK, bought a few lenses before I realised that the 350 had 1.6 crop factor and finding I am not getting quite the nice wide scenery shots I would like. Learning at the time so lenses bought are keepers. They are OK but just think I need one more for the bag. Very amateur and not loaded so keeping it sensible.

So, to get my head around this, as I look at it if I get a 28mm it is effectively a 50 (44) with the crop factor? If I go lower am I right in thinking that although I will get to a lower than 44mm by an amount, the lens will distort? This is for fixed focal lengths not zooms.

I am also finding that the field of view for my 28-135 is giving me different results for the kit 18-55 on a similar setting and would the fixed have a wider FOV for a comparable setting in those two?

[markmullen]

With a 350d you can use EF-S lenses, I believe the 10-22 is well regarded as an EF-S ultra wide.

[anonymous-user]

jmorgan said:

I am also finding that the field of view for my 28-135 is giving me different results for the kit 18-55 on a similar setting and would the fixed have a wider FOV for a comparable setting in those two?

I could be wrong, but I think it's because some lenses are made specifically for crop sensors (your 18-55 kit lens) so they give the correct FOV when used on a crop, but your 28-135 might be a 'standard' lens and therefore give a different FOV when used on your camera.

For example I have a D90 which uses a crop sensor, and I have an 18-200mm 'DX' lens for it. In Nikon-speak DX lens means specifically for crop sensor cameras meaning the FOV comes out correct so to speak.

I also have a standard 50mm Nikon lens (Not DX) which when used on my camera gives a FOV of more like 70-80mm.

So I think what you are seeing is normal.

[K12beano]

NinjaPower said:

For example I have a D90 which uses a crop sensor, and I have an 18-200mm 'DX' lens for it. In Nikon-speak DX lens means specifically for crop sensor cameras meaning the FOV comes out correct so to speak.

IMHO, whenever Nikon quotes a focal length (and for the sake of this can we ignore that lenses are not always necessarily *exactly* the focal length they claim to be) it means THE focal length. The actual sensor size is immaterial to the focal length. However whether a lens is designed for "FX" or "DX" is related to the image circle it will produce at the plane of the sensor.

[jmorgan]

Ta. Much to mull over, looking at one or two sub 28. Bit of a deeper topic than I thought. Need to go and look up some more numbers. Looking for something that will give me the sweeping vista's but not the effects of a fish eye.

Not thought about the kit being made for it, thought it was the standard off the shelf for canon.

Re 10-20, few of them coming up in searches, better go and look see what they look like on flikr.

Cheers.

[jmorgan]

markmullen said:

With a 350d you can use EF-S lenses, I believe the 10-22 is well regarded as an EF-S ultra wide.

Penny dropped now, an evening spent perusing the sites and I should have looked at Canon first for an explanation. Got it.

[RobDickinson]

Just to make a certain point 100% clear.

Every (SLR) lens is described in terms of its focal length. This is regardless of sensor size, or what body its on.

18mm is 18mm. Be it on a crop or a FF body.

18-55 is 18-55. 28-105 is 28-105.

Technically theres more to it than multiplying the focal length by 1.6 but for most purposes this is fine.

Using a FF lens on a crop doesnt cause any more distortion, 28mm (effective 44mm) isnt any worse on a crop body, in fact its possibly better as you are using the sharper centre of the lens.

Now 18mm isnt hugely wide but is wide enough for most shots, the 10-22 (or alternatives) are great lenses but can take a little effor it using correctly IMO.

[jmorgan]

Cheers. I am listening.

[tim-b]

The way I understand it is as follows;

When you use a cropped sensor you are getting exactly the same image as you would with a FF sensor, albeit just the centre portion (i.e. the image from the lens overlaps the sensor area). Which should look pretty similar to using the FF to 'zoom in', since the sensor remains in the same position relative to the scene, so same image but you're just seeing the centre of it.

I think something that may throw this off is that the EF-S lenses have a slightly different architecture (to enable them to be smaller IIRC) which is why they don't physically fit the FF bodies. I guess various lens characteristics may also make a subtle difference.

I'm no expert though so quite prepared to be corrected!

[billbring]

jmorgan said:

Re 10-20, few of them coming up in searches, better go and look see what they look like on flikr.

The EF-S 10-22mm is a very good quality lens and built specifically for crop sensor bodies, giving you an equivalent of 16-35mm.
Funnily enough I posted a few pictures from it combined with a 350d in this thread, yesterday, so you can see exactly the kind of thing you should expect.

The only thing is that it's not cheap at around £600. I hired it for my trip to Berlin for about £50/week (shorter hire periods are available) which might be an option if you want to try it out first. It is the lens that I'm planning to buy next, as for me it proved very versatile and I believe it will be perfect for high quality landscape photography.

If you want any more examples of shots then let me know.

[jmorgan]

Cheers, looking at them and flickr has convinced me. Didn't think of hire though, limit on where they can go and insurance and all that will need looking into. May just buy it.

[jmorgan]

Well there is a thing. Work got in the way again but Tamron do a lens for the smaller sensor as does Sigma. Tamron looks the better bet on balance and loot.