Art and Photography

Should you use Full Frame Lenses on Crop Bodies?

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  • Dec 12th, 2014 6:15 pm
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Should you use Full Frame Lenses on Crop Bodies?

So I ran into this video today from Tony Northrup that's totally change the way I think about lenses. I'm sure that like his video on crop factor I think it will be controversial, but I thought it was a really good watch.

http://youtu.be/YDbUIfB5YUc

Previously I encouraged people to buy FF lenses (especially primes) in case they want to upgrade to FF later on. Now I may not. I guess the only thing that I have to add is that there are fewer good quality APS-C options for lenses but I guess there's not much we can do about that.
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You're obviously not gonna get as good of results on a crop body than a FF one. But if you want a 2.8 zoom lens, even if you get, for example, the Tamron 17-50 f/2.8 APS-C lens, you're still going to get the same aperture disadvantage as the Canon 24-70 f/2.8. Sure you'll get the correct focal length for your crop body now, but it'll still be pointless if you want to upgrade.

The encouragement of buying FF lenses in case of an upgrade is still a very valid idea. You just have to be weary of the results and the drawbacks you'll get when you it put on a crop body now.
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Something similar happen if you have a FF body and use it with APS-C lenses.

It may depend on how much you're willing to spend.

The way I see it (in a rough way and without considering technical specs):

a) APS-C body + APS-C lens = cheap alternative, decent pictures (many people start with this combination)
b1) APS-C body + FF lens = better IQ than (a) at a moderate cost, but still cheaper than (b2) (eventually some move to this)
b2) FF body + APS-C lens = somewhat similar IQ than (b1), still moderate cost but not using full potential of FF body (people don't usually go this way)
c) FF body + FF lens = costly but with better IQ
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gontori wrote:
Dec 12th, 2014 10:37 am
Something similar happen if you have a FF body and use it with APS-C lenses.

It may depend on how much you're willing to spend.

The way I see it (in a rough way and without considering technical specs):

a) APS-C body + APS-C lens = cheap alternative, decent pictures (many people start with this combination)
b1) APS-C body + FF lens = better IQ than (a) at a moderate cost, but still cheaper than (b2) (eventually some move to this)
b2) FF body + APS-C lens = somewhat similar IQ than (b1), still moderate cost but not using full potential of FF body (people don't usually go this way)
c) FF body + FF lens = costly but with better IQ
huh??? I don't think you get it

a) APS-C body + APS-C lens = cheap alternative, decent pictures (correct)
b1) APS-C body + FF lens = Often no better image quality than A (in some cases it's actually worse) with the exception of the most expensive lenses. It is however more versatile in case the photographer decides to go full frame later.
b2) FF body + APS-C lens = This just makes no sense. Very few APS-C lenses will work on a FF body. Most will have a small image circle in the center of the frame, some won't even mount. If you did crop your image to the size of the image circle then you'd have an extremely low MP image, which would look fairly bad.
c) FF body + FF lens = costly but with better IQ (correct)
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da_guy2 wrote:
Dec 12th, 2014 11:02 am
huh??? I don't think you get it

a) APS-C body + APS-C lens = cheap alternative, decent pictures (correct)
b1) APS-C body + FF lens = Often no better image quality than A (in some cases it's actually worse) with the exception of the most expensive lenses. It is however more versatile in case the photographer decides to go full frame later.
b2) FF body + APS-C lens = This just makes no sense. Very few APS-C lenses will work on a FF body. Most will have a small image circle in the center of the frame, some won't even mount. If you did crop your image to the size of the image circle then you'd have an extremely low MP image, which would look fairly bad.
c) FF body + FF lens = costly but with better IQ (correct)
That's why I didn't want to get into technical specs. Of course if you want to compare cheap glass and high quality glass, then this changes. Same as cheap bodies vs. high quality bodies.
This is again, a rough idea in terms of money to spend or invest.

When you said "This just makes no sense" is the same what I meant. People don't go this route because the body will not take full advantage of an APS-C lens.

For people who want to upgrade, unless they want to spend big money, then can do it altogether: FF body and FF lens.
But if money is the main issue they upgrade by parts, either they get a FF body and then the lenses, or the lenses and then the body.
There's no hard rule in here. Nobody tells you to get this first and then get that second.
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the only time it makes sense is to fill the gaps in the APSC lenses that the manufacturer left. Nikon's DX APSC lens lineup is lacking a lot of lenses

You get a slight improvement in vignetting with the FF lens, but I've never been tempted to buy FF lenses for my D7000
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I have a problem with Tony Northrup laying down these "rules". I find it hard to believe that the Canon 7D + Sigma 18-35 is "sharper" than the Canon 7D + Canon 24-70 II.

http://youtu.be/YDbUIfB5YUc?t=4m42s
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thericyip wrote:
Dec 12th, 2014 1:18 pm
I have a problem with Tony Northrup laying down these "rules". I find it hard to believe that the Canon 7D + Sigma 18-35 is "sharper" than the Canon 7D + Canon 24-70 II.

http://youtu.be/YDbUIfB5YUc?t=4m42s
I have no problem believing it. Think of it this way. The 24-70 is designed to spread the projected image over an 860mm^2 area. Without making the lens insanely large, or insanely expensive there is a theoretical maximum resolution for that lens. Another way you can think of this is in terms of data. The light entering the lens contains data about the image. The lens "processes" the light data and sends it to the sensor to be displayed. In order to increase the amount of light data you can either capture more light (i.e. bigger front element), or do a better job processing the light (i.e. better optics), but there come a time when the lens gets either too big or too expensive.

When you put that lens on a crop body with a sensor area of just 370mm^2 much of the projected image doesn't hit the sensor. If we think of this in terms of data, much of the light data is being lost as it doesn't fall onto the smaller sensor. An APS-C lens however is designed with the understanding that it will be placed on a camera with a smaller sensor, so instead of wasting the light data it focuses all of it onto the smaller sensor. Sure it's not perfect, which is why the Canon 7D + Sigma 18-35 isn't as sharp as a Canon 5DIII + Canon 24-70 II, but it's a lot better than just wasting the light data.

Another example of this is a the metabones speedbooster. This does the same thing, it refocuses the image produced by a FF lens onto an area the size of an APS-C sensor. This increases the brightness of the image, give a shallower depth of field, and increases the apparent sharpness of the lens. Essentially it an APS-C sensor the look and feel of a FF sensor.
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As long as you need to crop, FF lens on Crop sensor is better. Also FF L lenses are typically better glass then Crop kit lens.
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you're using the best part of the FF lens if on a crop body, if you can afford it by all means do it.
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You're using the best part of the FF lens on a crop body, but if you're never gonna upgrade that you're paying a premium for that.

I'm happy with my crop body and crop lens. Small, light, decent quality (D7000 + Tamron 17-50/2.8). May consider picking up that Sigma 18-35/1.8 but that's really pricey.

FF is obviously nicer, but I suppose I don't think that extra quality is worth the drastic jump in price.

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