Last week I clarified a very common question about buying a fixed focal length for APS-C sensor SLR. Today, I would like to defeat a common idea (Think of the “Full Frame Camera” When buying a lens?), or at least to shade it strongly, because I read a lot of wrong things, and it can mislead many beginners.
I will not make an umpteenth reminder about the influence of sensor size, because I have already done so in the previous articles, and above all I invite you to read my full article about sensor size. To fully understand this article, you must have this notion in mind.
Should I Buy A 24-70 mm F/2.8 On APS-C?
The advice that I see the most and that prompted me to write this article, is the one that is sometimes given to beginners who want to buy a quality versatile trans-standard zoom to replace the 18-55 mm of the kit, limited in terms of brightness especially.
And here, we see from time to time advice that consists in recommending a 24-70 mm f/2.8, or even a 24-105 mm or 24-120 mm f/4. And that's a very bad idea. Far from me the idea of throwing a flurry of pebbles coated with fresh nettles to these advisors is probably in good faith. Indeed, the 24-70 mm f/2.8 and cousins, even in third-party brands like Tamron and Sigma, are often excellent lenses, with good image quality and good brightness.
They are also very versatile in terms of focal length, but on full frame reflex. Indeed, 24-70 mm on Full Frame corresponds to a range of focal lengths extending from a true wide-angle (24 mm) to a small telephoto lens (70 mm).
On the other hand, on APS-C sensor, we get something equivalent to about a 35-105 mm on Full Frame (about I said, no need to do the calculation to the nearest mm in comment, it does not change anything at schmilblick, thanks 😉.
Question: Have you ever seen a 35-105 mm zoom? No. Why? Because it's useless.
The big problem is that with a 24-70 mm on APS-C, you will certainly have a real telephoto lens (small, but at 105 mm it is perfect for portrait). On the other hand, no real wide-angle, which significantly reduces versatility. You will lack view angle for all landscape or architecture type photos for example, or even just situations where you lack recoil. In short, you will have lost all the versatility of the focal length of your 18-55 mm, and you may be frustrated.
The only situation where it can possibly be justified is for a strictly portrait use: if you want to be able to comfortably portrait both in feet and tight with one and the same lens, the focal range will be quite ideal for the shot: 35 mm (equivalent 24×36) for the portrait in feet, and 105 mm for the tight portrait. But it's a pretty specific situation anyway (and where I'd prefer 2 fixed focal lengths for their greater ability to make a shallow depth of field).
The justification for "thinking about the full frame" does not hold here: you do not know when you will actually spend there (if you spend a day there), and I do not see the point of disabling yourself photographically speaking for a (long) moment, just to save the loss on resale in the totally hypothetical event where you would buy a full frame reflex soon (which still generally cost $2200 minimum, so anyway it's a big budget).
What to Choose Instead?
So, you're going to tell me, "that's beautiful Devansh, you're telling us that you shouldn't take 24-70 mm on APS-C, but what do I do if I want a versatile and bright zoom to replace my 18-55 mm that limits me?
Well it's pretty simple in fact: you need about the same range of focal lengths, but with a constant maximum aperture of f/2.8. There are many lenses to satisfy you, usually 17-50 mm f/2.8.
I'm not going to make you a list in the pervert or a detailed comparison here, this is not the topic, but for example for less than $300, you can have the excellent Tamron 17-50 mm f/2.8, which does its job very well.
I resold it for $200 not long ago, so I lost less than $100 on resale, which is not much when you consider the price of a full frame reflex actually, especially since it has made me proud service for a long time.
And 17-50 mm on APS-C, very surprisingly, it gives an equivalent 24-70 mm (approximately). Eureka!
What About the Fixed Focal Points?
That was for zooms, but what about fixed focal lengths? So, I already talked about the special case of the 50 mm last week, but here I would like to return to a slightly more general case.
First, I think that the question of "thinking about the full frame" only arises if you know that you will turn to this format very soon, that is, in less than 6 months, or even 1-year max. Beyond that, honestly, it's perfectly hypothetical. You do not know what will happen in a year, either in your own photo practice (you could switch to the hybrid or on a compact large sensor), or in the photo market (it could appear a compact Full Frame with a bright trans-standard zoom after all.).
So, in case you really think about it, there you can legitimately ask yourself the question.
Let's imagine that you have an APS-C reflex, with a 50 mm (equivalent 80 mm) and an 85 mm (equivalent 135 mm), because you like the portrait. With this you really cover all your needs. On the other hand, you would like to have a more standard focal length for making foot shots or other photos. So, you're thinking of the 35 mm, which would give a 50 mm equivalent on your APS-C. But in 3 months, you're thinking of buying a full frame reflex. And there you will already have a 50 mm as a standard focal length. If you only do portrait, a 35 mm on full frame could be a bit wide (it depends on your use).
In this case, you should rather think about waiting for the Full Frame to buy say a 135 mm, which will allow you to find what you were used to with the 85 mm mounted on your APS-C.
This is just one example to point out that it is once again a matter of photo needs and practice. I can't decide for you, I'm not your mom and you are responsible adult, but I can help you think hard to make a better decision.
In short, "thinking about the full frame" is often premature or even counterproductive, especially with regard to zooms. So think carefully and do not throw yourself on the first lens advised by a stranger on a forum, under the pretext that it is "an excellent lens" (which is always relative). And which does not mean to throw your 24-70 mm if you have an APS-C, but not to be surprised if you sometimes miss a step back. 😉 😉 😉