Lens math question....
I've been thinking about a 24-70 f/2.8 for quite some time now, but just recently started to think about something that I have no earthly idea how to calculate. So I figured the 'experts' here could help!
In a nutshell, some have said a 24-70 is not worth the coin to toss in the bag when a 50mm prime will suffice and you adjust by moving forward or backwards from the subject. I didn't say it - I just read it with the understanding that a LOT of the decision would depend on the type of work you do.....
Assumptions:
1) You have a 50mm prime on a full-frame/no-crop body such as a D700.
2) The camera is on a tripod.
3) Your subject is some fixed distance away, centered and in focus. Let's use 20' for the exercise.
4) I think f/stops, shutter speeds, modes, etc. won't matter for this.
The question is this. If you take the above scenario, what kind of distances are we talking about moving the tripod/camera forward and backward to achieve the same frame view at 24mm and 70mm focal length compared to the 50mm?
Is the statement above about moving forward or backwards towards the subject even practical at that point? (not knowing the answer, I guess we'll find out and decide....)
An interesting question, eh?
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In a nutshell, some have said a 24-70 is not worth the coin to toss in the bag when a 50mm prime will suffice and you adjust by moving forward or backwards from the subject. I didn't say it - I just read it with the understanding that a LOT of the decision would depend on the type of work you do.....
Assumptions:
1) You have a 50mm prime on a full-frame/no-crop body such as a D700.
2) The camera is on a tripod.
3) Your subject is some fixed distance away, centered and in focus. Let's use 20' for the exercise.
4) I think f/stops, shutter speeds, modes, etc. won't matter for this.
The question is this. If you take the above scenario, what kind of distances are we talking about moving the tripod/camera forward and backward to achieve the same frame view at 24mm and 70mm focal length compared to the 50mm?
Is the statement above about moving forward or backwards towards the subject even practical at that point? (not knowing the answer, I guess we'll find out and decide....)
An interesting question, eh?
.
0
Comments
That said, I find the 24-70/2.8 to be a slightly awkward lens on a full frame body. An f/2.8 lens is for shooting people (mostly anyhow) because that is where you need the speed. Personally I shoot with primes and the focal lengths I use for people photography are 35mm, 50mm, 85mm and 135mm. If I wanted to use zooms to cover that range I'd have 2 large, heavy expensive lenses and I'd still be changing lenses all the time (or use two bodies). Since I am going to be changing lenses anyhow (I only have one body), I figure I might as well shoot with primes and gain a stop or two in speed (all my lenses are f/2 or faster) and save on weight. If there was a 35-105/2.8 I might think differently, but the 24-70 and 70-200 pair just don't work for me.
Moderator of the Cameras and Accessories forums
The argument (as I've seen it) isn't really that a 50mm lens replaces a 24-70mm, but rather than with a few small, lightweight primes and "zooming with your feet" you can do everything you really need to do that you might otherwise do with two large, heavy zooms like EF 24-70mm f/2.8L. and 70-200 f/2.8L (or three zooms if you add in the 16-35mm f/2.8L). The zooms undeniably provide more flexibility, but the question is how often you really need that extra flexibility, as opposed to just taking advantage of it out of laziness. For most purposes, I find that composition is not adversely affected by having to move a bit to get the right framing at 35mm or 50mm rather than, say, setting your zoom to 42mm.
LiquidAir, I don't think your argument that telephoto lenses have shallower DOF is valid because the difference in DOF between 50mm and 70mm is compensated for by the two-stop aperture advantage of the 50mm f/1.4.
I see focal length as simply a matter of tighter or looser framing from a given shooting position. Composition (including perspective) is defined by where you place the camera in relation to the subject and surrounding objects; focal length controls the size of the frame (the width of the field of view); aperture adjusts DOF from the baseline established by focus distance and focal length; shutter speed and ISO can be selected for proper exposure and the desired degree of motion freezing or blur. Naturally you can't always get exactly what you want in all those parameters at once, but as with the use of prime lenses, you can usually get close enough that it doesn't matter.
Got bored with digital and went back to film.
In my youth, my first personal camera was a Pentax H1a, manual focus and manual exposure, 35mm format film camera. My first lens was a 50mm, f1.7 prime. I used that for a couple of years and learned to think of the world through that 50mm lens "window". While it was freeing in a way, composition and framing became almost second nature to previsualize, it was also limiting for spontaneous "grabs" of dynamic situations.
Imagine my glee when I started using zoom lenses where I could compose and frame more quickly in the camera, more effectively isolating the subject(s) in motion, or while I was in motion. This opened new avenues of opportunity, but the lenses I could afford and that were available were pretty slow apertures so I still used the prime for indoor and lower light situations.
Flash forward to today, with fast primes and reasonably fast zoom lenses too. My selection is based on the venue and subject matter. As LiquidAir said primes are so very nice when you have the opportunity for time, but in dynamic situations I almost always go for a zoom in the range appropriate to the venue and situation.
I would hate to be limited to one methodology all the time. The concept of interchangeable lens cameras is to allow changing the system to meet the needs of the situation. I recommend purchasing lenses that meet the needs of your given situation. By all means develop a flexible shooting style that "allows" moving your position to meet your imaging needs, but I would not recommend purchasing a system that "depends" on your having to constantly move to satisfy the shooting situation.
Moderator of the Cameras and Accessories forums
The Canon 24-70 f2.8 is a unique lens, loved by some wedding shooters, and hated by others. It is large, heavy, and not a favorite of mine out of doors where I prefer the lighter, smaller, longer 24-105 f4 IS L. It is indoors where the faster 24-70 f2.8 - on a full frame body shines. It can be very sharp as my copy seems to be. It will capture every thread in a bridal veil.
I find I rarely use my 50f1.4 unless I am shooting in the dark.
I find when I am shooting with primes, I do not want to stop and swap lenses - too slow, too much time and aggravation. I prefer to use two bodies when shooting with primes, maybe a 35f1.4 and an 85 f1.8 or a 135f2.0 L.
Moderator of the Technique Forum and Finishing School on Dgrin
The quick answer here is that, shooting with primes my choice is a 50/1.4 or an 85/1.8. If I was shooting with a zoom, the choice would be between a 50/2.8 or a 70/2.8.
The deeper answer is that when you shoot with a wider lens a few things change at the same aperture. The first is that the hyperfocal distance moves closer the the camera. The second is that the amount of blurring at infinite distance is proportional to aperture size rather than the f number.
Here are the lenses I use with their aperture sizes (wide open)
35/1.4 : 25mm
50/1.4 : 35mm
85/1.8 : 47mm
135/2 : 67mm
200/2.8 : 71mm
When I switch to a longer focal length lens I get both more depth of field (because of the larger f-number) and more background blurring (because of the larger aperture). The net result is that the subject is sharper and the background is softer both of which contribute to isolation of the subject.
There isn't any right or wrong as to primes or zooms ... it is all your personal tastes as to which works best in your hands. I used to be a photo journalist in the film-only days, back when auto was a car not a camera mode. Back then zooms where horrible, they were slow, soft and distorted. So I shot everything with primes ... walked around with a heavy bag ... constantly changing lenses and cameras ... and it wasn't a big deal then ... and it's not a big deal now.
Okay ... I'm rambling ... the bottom line is that with the sharpness and relatively fast zooms of today ... you now have a choice. While both camps have advantages and disadvantages (zooms are amazingly useful while primes are sharper and faster). Will the difference between 1.8 vs 2.8 be significant (for most of us probably not) ... is the difference in resolution which can only be visible at 100% significant (probably not for most of us).
So go rent a 24-70 and shot some stuff ... then try shooting with primes ... It is all about you and your expectations ...
Gary
Unsharp at any Speed
I'd like to say "Thanks" to all of you for the replies. I've learned a lot of good information as well as confirmed some thoughts (and dispelled others) all at the same time. What a great place this is!
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Natural selection is responsible for every living thing that exists.
D3s, D500, D5300, and way more glass than the wife knows about.