70D question

[newshooter]

This is probably going to be a really dumb question, but I am going to ask anyway.  I just bought my first dslr camera, the 70d, and it's all a bit overwhelming for a newbie.  I intend on buying one of the DVD sets that explains the cameras features but in the meantime, the one thing I haven't been able to find in the manual or by clicking through the cameras menu is this, and it's my dumb question;

I will use this camera for wildlife photography and while watching the numerous camera review videos before I made my purchase I heard where they kept talking about how this camera has a crop sensor of 1.6x and by using this feature it would turn a 255mm lens into a 408mm lens?  Ok, so is this a feature you turn off and on or is this camera just always using this crop sensor?  And I think crop sensor was the correct term?

[TCampbell]

It's not a feature that you turn on and off... the sensor size is what it is.  It's one aspect of your camera that never changes.

I'll try to explain.

A "full frame" sensor simply means that the digital sensor is the same size as a single frame of 35mm film.  That size is roughly 36mm x 24mm.  A "full frame" Canon body would be either a 6D, 5D III or 1D X (not listing any of the cameras that Canon no longer markets).

Your camera has an "APS-C" size sensor.  That means the digital sensor is roughly the same size as a single frame of APS-C film.  APS-C is "Advanced Photographic System - Classic".   A frame of that film is slightly smaller... about 22.5mm x 15mm.  The APS-C crop-frame bodies from Canon include all the Rebel bodies (T3, T3i, T5i and SL1) as well as the mid-range 60D, 70D, and 7D.  Also, the EOS-M is an APS-C body (though that's a mirrorless camera or "MILC" and not a "DSLR").

The lenses, however are the same.  You can use the same Canon EF series lenses on your camera (and all Canon EOS cameras) as you can on a full-frame camera.  The EF lens projects the same physical size image circle into the camera body on your camera as it does on a full frame camera.

The APS-C cameras can also use Canon's EF-S lenses.  More on this later in the post. 

Since the sensor on your camera is physically a little smaller, it means a bit more of the image "spills off" the sides and is not recorded as part of the image.  

The APS-C format size is referred to as a "crop factor" because it's as though you took an image from a full-frame camera, cropped in to just use the center area... but then enlarged the print.  It makes it *seem* as though you enlarged the image ... or "zoomed in" a bit more.

The crop factor is 1.6.  This means that if you were to shoot a subject at the same focal length (suppose you use a 50mm lens) with a full-frame camera, and then again with the 70D, it will look as though the image from the 70D was zoomed in by 60% -- effectively the 50mm lens will look a bit as if we had used an 80mm lens on the full-frame camera.

So now that we've established that the "crop factor" on the sensor means you get a narrower angle of view... and that the narrower angle of view makes it seem as though you've zoomed in a bit, that seems to work in your favor at the "long" end (when you want a long telephoto focal length).  BUT... what happens when you want the opposite?  What happens when you want a wide-angle lens?  Now the crop-factor works AGAINST you.   It makes an otherwise wide angle lens (on a full-frame body) seem not so very wide at all.  Canon offers a different set of lenses that deal with this issue -- those are the EF-S lenses.

The EF-S are lenses specifically made for the crop-frame sensor cameras.  I have a Canon EF 100mm f/2.8L IS USM Macro lens for my 5D III -- it's a nice macro lens.  But for the crop-factor bodies, Canon makes the EF-S 60mm f/2.8 USM Macro.  It turns out if you multiply 60mm x 1.6 you end up with 96mm -- which is VERY close to the 100mm focal length Macro that they make in the EF series.  These two lenses provide roughly equivalent angles of view on their respective crop factor bodies (of course you can ALSO use the EF 100mm macro and get an even tighter angle of view.)

So back to your question...  you take the focal length of the lens, multiply it by 1.6, and that gives you a full-frame equivalent (technically it's not equivalent) -- 250mm x 1.6 = 400.  So it would be a bit like using a 400mm lens on a full-frame camera.

Here's an article at Cambridge in Colour that discusses it:  http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

Here's a video that discuses it:  https://www.youtube.com/watch?v=yAdI5BBgFHQ

[ebiggs1]

Tim has given you a fantastic explanation of the 1.6 "crop-sensor" included with the 70D.

One extra point that seems to sometimes escape new photographers, the lens' focal length never changes just because it is attached to a crop sensor camera. Only the apparent focal length is effected.

[newshooter]

Thank you both for a very detailed and easy to understand explanation.  That certainly clears it up for me and I now understand how it works.  Thank you again. 

I am really excited about this camera and I'm really looking forward to using it in the field.  I typically take pictures of deer from 15 yards out to 150 yards, sometimes further, but 95% of the time it's in those ranges.  Often it's at dusk or dawn as the deer tend to move best at those times, so I'm really eager to learn how to use the settings in order to get the most out of the camera.  I've always been one of those 'point and shoot' guys with the camera set on auto mode.  I take a lot of pictures and have gotten pretty good at it, even with my limited knowledge and inferior equipment.

Thanks again, I am in your debt.

My next research question will be in regards to which lens to use?  I'll search the forum first to see if it's already been addressed.  Fixed lens vs telephoto

[Yorptunes]

Dee be sure to check out the WIFI feature of the 70D.  It can allow you to pair the camera with a smart phone and then remotely trigger the camera at distances of 140-180 feet.  It could be a tremendous feature in getting some really close deer shots with your camera. 

John  

[amfoto1]

Hi Dee,

The above responses do a great job discussing what "crop sensor" means and how it applies to your camera.

Now I'm going to suggest you just forget it and don't worry about it very much in the future. This is not to dispute the above or discount the good info they are giving, but because "crop vs full frame" really doesn't have much effect on you, personally, as long as you are shooting with your 70D.  

Your 70D is a "crop sensor camera" which actually means it can use all EF-S and all EF lenses. In other words, basically everything that Canon makes as well as all lenses that third party lens manufacturers make to fit on Canon. (It would only be important to know the distinction if you had purchased a "full frame sensor" camera such as the 6D or 5D Mark III, which can only use EF lenses, that are full frame compatible.)

It sounds as if you bought the EF-S 55-250mm lens.... Which is a good, relatibely inexpensive lens to start with and is designed for crop sensor cameras only. It's a moderately strong telephoto. Eventually for wildlife photography you might find you want a stronger telephoto and there are many to choose among (pretty much all at higher prices, of course). Canon offers the EF 300mm f4 IS, EF 100-400mm IS, EF 400mm f5.6.... Sigma makes the 120-400mm OS, 150-500mm OS and 50-500mm OS. Tamron has announced a 150-600mm VC lens they will be offering soon... and there are quite a few others at even higher prices.

There are also teleconverters that can be added to some lenses, to increase their focal length. For example I often use a Canon 1.4x "Mark II" teleconverter with an EF 300mm f4 IS lens, which makes it an "effective 420mm f5.6" lens. A teleconverter can be a helpful addition for wildlife photography, but not all lenses can be fitted with teleconverters and some others simply don't work well with them. Of the above listed lenses, the 300mm is one of the few that will both give good image quality and still autofocus properly with a 1.4X teleconverter.   

Being new to your camera, I suggest getting one or more of the "guide books" specifically for the camera. This and the manual that came with it will help make sense of it. I have 30+ years experience with cameras of all types, but always make a point of getting a guide book for any new model I buy. The guide can be a real short cut to getting the best out of the camera, as soon as possible. From personal experience I can recommend guides by Charlotte Lowrie, Michael Guncheon, and David Busch... though I'm sure there are some other good authors, I am just not familiar with them. 

If you are new to photography in general, or just wanting to start taking it more seriously, I also highly recommend the book "Understanding Exposure" by Bryan Peterson. It's not specific to any particular brand or model of camera, but by the time you learn all it offers, you should be able to pick up and use virtually any camera reasonably well. I've read it several time and it's taught this old dog some new tricks!

Have fun!

***********
Alan Myers

San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM 

[newshooter]

Again, you all are giving me some great information and I'm going to take it all to heart and learn from it.

I know I was watching one guy on youtube, can't remember his name, and he specializes in wildlife photography.  By the sound of it, he is a bird man? 

But he mentioned going with a 400 prime lens vs a 100-300 style lens?  He flat out said, for wildlife photography, do not go with a telephoto, go with a 400 prime.

My question is, and I plan on researching this more on my own, how do I capture a deer at 15 yds or at 100 yds with a 400mm set lens? 

Remember, I'm not getting paid for my pictures so they won't be going in a magazine anytime soon. He's obviously a pro and needs that perfect shot, I get that, but I'm not there yet. 

And yes, I got the 70d camera body with the 18-55 stm lens, as well as the 55-250 stm.

[ebiggs1]

Mr newshooter, I encourage you to go out and shoot some pictures. Shoot a lot of pictures as doing is better than any book reading. Make sure you take note as to what you are doing. What you have will work just fine.......for starters.

Yes the 400mm prime may be slightly sharper than the 100-400mm zoom but you give that up because of no IS. I have both and the 100-400mm wins most of the connection time on my cameras.

The two shots below were taken with a 24-105mm f4 and the other with a 50-150mm f2.8.

24-105mm f4

50-150mm f2.8

Go out and shoot, man, that is the fun of it. Great shots a re everywhere.

[newshooter]

Oh, I'll be in the woods before sunup in the morning and hope to have some deer in front of me when it does.  And again next week with my daughter as she hunts also.  I hope to have it down well enough by the end of the month when I guide a veteran as he deer hunts for 4 days.  I will take pictures and video of his entire hunt then put it on a disc for him.

I just have to work a real job so I can support my hobbies!   

I have some pups for sale and need to take pictures of them today for my website, so that should be another good learning experience for me.  You ever try to get an 8 week old pup to sit still for a picture? much less 5 of them 

I will be saving up my money for probably a teleconverter and then a higher quality lens. 

My website has some pics of what I do with a camera and the action shots I take with my dogs in action.  Not sure I'll be toting the 70D on my hog hunts though, at least not for the normal action I get into?  Maybe for the after action shots?

But when I'm not hunting, I will be reading and reviewing as much as I can.  My partner here at work is a Nikon man and has both the D80 and the new D800, so he has been giving me some pointers but he has no experience with Canon. 

[newshooter]

This is what I'm used to with my Nikon Coolpix.

Deer at 18 yards, not the best of lighting, but still a good picture.

and what I want to do better at....85 yards, dusk, poor light....

And then, after the shot....

And with what should be plenty of light, a blurry pack of javelina