Zoom Lenses and Crop Factor

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ste1010

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Steve
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Hi
Looking for a cheap zoom to go on my 550d.

Was looking at something like a used 70-210 f3.5-4.5, 100-300mm f4.5-5.6 USM, or possibly the 55-250.

I am aware that on a crop body such as the 550d the focal length of a standard lens is multiplied by 1.6.

However the 55-250 lens is built for crop bodies so the question I have is as follows.

I assume that the max focal length of the 70-210 is 336 mm and the 100-300mm is 480mm.

Does the same apply for the 55-250 i.e is the max focal length 400mm, or is the multiplication not applicable as this is made for a crop body.

Hopefully the above makes sense.

Regards
Steve
 
EF-S lenses are constructed specifically for crop bodies. If you notice the rear element of the lens is slightly raised as opposed to an EF lens, which brings it closer to the camera's sensor. This is done to make it easier to construct wide angle lenses and also the lenses can be lighter, cheaper etc.

The multiplication is still applicable, the difference is that you cannot mount an EF-S lens on a full frame body.

While some might consider a 24-70mm lens to be a 'standard' wide angle lens on a full frame, the same lens on a crop would obviously not be wide. Hence the existence of the 18-55mm EF-S lens which provides approximately the same FOV.
 
The focal length of a lens is the focal length of a lens, it doesn't change. But the effective focal length can be changed by the size of the sensor in the camera.
Lots of useful threads about this if you have a quick search.
 
Thanks for the replies,

So if I understand, the effective focal lenght of the 55-250 will be 400mm irrespective of the fact eht EF-S lens is made for a crop body.

cheers

steve
 
ste1010 said:
Thanks for the replies,

So if I understand, the effective focal lenght of the 55-250 will be 400mm irrespective of the fact eht EF-S lens is made for a crop body.

cheers

steve
Click to expand...

Yep, focal length is a physical optical attribute, not affected by the sensor you put behind it.

So you always have a 55 to 250mm lens, however the field of view will appear similar to an 88 to 400mm lens if it was used on a 35mm sensor. It will still perform like a 55 to 250mm lens in relation to depth of field, that doesn't alter.

This 'crop' factor isn't new, it is just something that the masses haven't been affected by as generally in the past people used a 35mm camera. However, there were the 120 cameras and the medium and large format options too (well there still are) and they had the same crop factor issues but people didn't really get so hung up on it as now. I think it is that we like to find a standard to compare to which is why we get the 35mm equivalent field of view.

As you progress you will worry less and less about this. I don't think to myself that I'm using a crop body today so what is the lens going to be in 35mm I just know how I want things to look and which lens will do the job.
 
Did you try to search through this board? This topic has been beaten to death here.
Or you could start from wikipedia as well http://en.wikipedia.org/wiki/Focal_length

In short:
1. Focal length is a characteristic of the optical lens, it DOES NOT depend on enything else, full stop.
2. Now, Field Of View (FOV) depends of Focal Length AND Sensor Size. For the same Focal Length, the larger the sensor is the wider the FOV is.
3. Because different cameras can have different sensor sizes, it was decided to introduce an Effective Focal Length, i.e. Focal Length which will give the same FOV on 35mm sensor (or film).

Once more: Sensor size DOES NOT change the Focal Length, it changes the Field Of View (FOV)

PS
to admins: Why not create an FAQ here for questions like this one?
 
The 55-250IS lens is a cracker of a lens for the price and you won't go wrong with it and will fit nicely with the kit lens...
 
gunnar said:
Did you try to search through this board? This topic has been beaten to death here.
Click to expand...

I did search through the board but couldn't find anything specifically around the EF-S lenses.

I guess I need to do a bit more reading, however, the posts here have answered my specific question. thanks for ll the responses.

Regards

Steve
 
Make sure you bear in mind that EF-S lenses won't go on a full frame body, in case you ever plan to upgrade in the future. :)
 
andyred said:
The 55-250IS lens is a cracker of a lens for the price and you won't go wrong with it and will fit nicely with the kit lens...
Click to expand...

Bingo, just buy that lens and enjoy, will give you a nice range coverage. Buy used and you can sell when you want to upgrade (70-200mm F4 non IS is the next logical step) and barely lose anything.
 
+1 for the above. I love my 55-250 on my 7D, I got mine from someone on here for £110 andits a cracker. The only problem is that I gave my 550D to my wife when I got my 5D2 and she keeps nicking my lens.
 
My Brother is looking to sell his 70-200mm F4 L.

To be honest its a bit more than I wanted to pay as the main reason for getting the camera was taking pics of my daughters gymnastics, and I have bought some lenses for that which I am happy with. I borrowed his 70-200 and found I had to crop quite heavily hence the reason for something a bit longer (and cheaper) hence the question about the 100-300mm and 55-250.

Cheers

Steve

I wanted a zoom for football and cricket, but was looking at something with a bit longer reach hence the question
 
Mark..I am using a 85mm f1.8. I generally am able to get pretty close to the action at comps. I have also picked up a nifty fifty for use at my daughter's gym club where sometimes I am too close for the 85mm.

I have only recently bought the camera/lens and only had it out once in her gym club and one competition. She has another comp this weekend.

There are a couple of pics in this thread

http://www.talkphotography.co.uk/forums/showthread.php?t=363838

I was originally looking at killing both two birds with one stone and getting a Sigma 70-200mm f2.8 but had heard a lot of stories of them having foccusing issues on Canon bodies. Also some people advised that f2.8 may not cut it in some gyms unless the ISO is cranked way high.
 
That's cool, I've used the 85mm f1.8 quite a lot, in some of the holes, I mean gyms, I've shot in I needed to go to ISO 6400 to make 1/640s so only offered prints up to 9" x 6" in such situations. I found for some floor work I could use a lens at f2.8 but not for tumbles etc and just depending on the gym. The higher the level of comp generally the better the light.

I've used a Sigma 70-200mm f2.8 and not had any focus problems, the main issue was it not being overly sharp at 200mm. The Canon 70-200mm f2.8 lenses are much much stronger.
 
I might of got the wrong end of the stick here, but its seems in one post you said you need more reach as the 70-200 wasnt enough for the gym work, but yet you use an 85mm?

Personally, you are going to need a 300+ lens for most sports. As Mark1616 said, for Cricket, you are going to need a beast.

The 55-250 is an amazing lens for the price, but not sure if that will give you enough reach.
 
mark1616 said:
That's cool, I've used the 85mm f1.8 quite a lot, in some of the holes, I mean gyms, I've shot in I needed to go to ISO 6400 to make 1/640s so only offered prints up to 9" x 6" in such situations. I found for some floor work I could use a lens at f2.8 but not for tumbles etc and just depending on the gym. The higher the level of comp generally the better the light.

I've used a Sigma 70-200mm f2.8 and not had any focus problems, the main issue was it not being overly sharp at 200mm. The Canon 70-200mm f2.8 lenses are much much stronger.
Click to expand...

I disagree. The sigma 70-200 f/2.8 is easily as good as the mk1 Canon (both non IS/OS variants). Not tried the mk2 Canon though.
 
odd jim said:
I disagree. The sigma 70-200 f/2.8 is easily as good as the mk1 Canon (both non IS/OS variants). Not tried the mk2 Canon though.
Click to expand...

I've used a few of the Sigma's and none have been as sharp wide open at 200mm as the Canon 70-200mm f2.8 IS, let alone the non IS which is just a little sharper again. My most recent was traded in only last Saturday as I had kept it as a backup to my Canon but it never got used.

Sure at the wider angles the Sigma is fine but when you are buying a lens that goes to 200mm and 2.8 you would like to use it.

Check out SLR Gear, they have some helpful stats to look at.

Oh, and I'm not a Sigma hater or anything, I use the 120-300mm f2.8 and love it, also the 17-70mm I have when I play with one of my crop cameras is also a rocking little lens, just in the case stated here, the Sigma falls short of the Canon options.
 
mark1616 said:
This 'crop' factor isn't new, it is just something that the masses haven't been affected by as generally in the past people used a 35mm camera. However, there were the 120 cameras and the medium and large format options too (well there still are) and they had the same crop factor issues but people didn't really get so hung up on it as now. I think it is that we like to find a standard to compare to which is why we get the 35mm equivalent field of view.
Click to expand...

Apart from the fact medium and large format cameras have an even larger area than 135 film so the 'effective focal length' is actually smaller, an image shot on 120 film with a 6x7 cm camera (for those who don't know this the negative size varies between 120 cameras, basically you get bigger images/less exposures with some types, 6x4.5 is the smallest and it goes all the way up to special 6x24 panoramic cameras) has a much larger negative so compared to 135 film the effective focal length is about 0.5x.

In the past of course people didn't bother with 'crop factors' (may not be quite the right word as its bigger!), it was just known that an 80mm lens was the standard lens for 6x4.5 120 cameras, a 105mm for 6x7, wide angles and telephotos were so and so etc...
 
s162216 said:
Apart from the fact medium and large format cameras have an even larger area than 135 film so the 'effective focal length' is actually smaller, an image shot on 120 film with a 6x7 cm camera (for those who don't know this the negative size varies between 120 cameras, basically you get bigger images/less exposures with some types, 6x4.5 is the smallest and it goes all the way up to special 6x24 panoramic cameras) has a much larger negative so compared to 135 film the effective focal length is about 0.5x.

In the past of course people didn't bother with 'crop factors' (may not be quite the right word as its bigger!), it was just known that an 80mm lens was the standard lens for 6x4.5 120 cameras, a 105mm for 6x7, wide angles and telephotos were so and so etc...
Click to expand...

True, I didn't go into my usual explanation of them being 0.x crops due to being bigger.... I get bored of writing so often about this subject and that makes me lazy :)
 
mark1616 said:
Yep, focal length is a physical optical attribute, not affected by the sensor you put behind it.

So you always have a 55 to 250mm lens, however the field of view will appear similar to an 88 to 400mm lens if it was used on a 35mm sensor. It will still perform like a 55 to 250mm lens in relation to depth of field, that doesn't alter.

This 'crop' factor isn't new, it is just something that the masses haven't been affected by as generally in the past people used a 35mm camera. However, there were the 120 cameras and the medium and large format options too (well there still are) and they had the same crop factor issues but people didn't really get so hung up on it as now. I think it is that we like to find a standard to compare to which is why we get the 35mm equivalent field of view.

As you progress you will worry less and less about this. I don't think to myself that I'm using a crop body today so what is the lens going to be in 35mm I just know how I want things to look and which lens will do the job.
Click to expand...

Agreed. This is a very common misconception - that the focal length increases on a crop camera - and it's probably still being pushed by some sales people. I don't think anyone bothered about it in the film days. The majority of people who used cameras with interchangeable lenses were using 35mm, and the comparatively few who used larger formats knew how their lenses performed. The lenses were usually wide, normal and short telephoto (by 35mm standards) anyway.
 
One point to remeber was that the lenses for medium format generally didn't fit the the 35mm cameras so the concept of a crop factor was less important. It became significant when the first generation of DSLRs such as the the Canon D30 were introduced and the only lenses initially available for those cameras were those designed for the full frame 35mm film cameras.
 
MJ Stebbings said:
I might of got the wrong end of the stick here, but its seems in one post you said you need more reach as the 70-200 wasnt enough for the gym work, but yet you use an 85mm?
Click to expand...

Not sure I said enaough reach on the 70-200, if I did, it was meant to say not fast enough.
 
mark1616 said:
I've used a few of the Sigma's and none have been as sharp wide open at 200mm as the Canon 70-200mm f2.8 IS, let alone the non IS which is just a little sharper again. My most recent was traded in only last Saturday as I had kept it as a backup to my Canon but it never got used.

Sure at the wider angles the Sigma is fine but when you are buying a lens that goes to 200mm and 2.8 you would like to use it.

Check out SLR Gear, they have some helpful stats to look at.

Oh, and I'm not a Sigma hater or anything, I use the 120-300mm f2.8 and love it, also the 17-70mm I have when I play with one of my crop cameras is also a rocking little lens, just in the case stated here, the Sigma falls short of the Canon options.
Click to expand...

Sorry I'm not sure I understand?

I get perfect results at f/2.8 @ 200mm. That's where I use it most.
 
odd jim said:
Sorry I'm not sure I understand?

I get perfect results at f/2.8 @ 200mm. That's where I use it most.
Click to expand...

Which part?

It's one we could go round in circles with, also our definitions of perfect are probably different too. None of the reviews has ever called it perfect at 200mm and f2.8 and all I can do is base it on my experience of using 3 of them over many years and also using the Canon options over many more.
 
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