[mee]

A image to illustrate the differences between a FF telephoto zoom and an APS-C telephoto zoom covering roughly the same view for their format aspects.

The other aspect can't be fully described in text -- the weight difference. The FF zoom is around 4 pounds in weight. The APS-C zoom weighs around 1 pound.

This is the reason I will always have a crop telephoto in my possession... the FF versions are huge and heavy comparatively.

I will use the Sigma for purposeful shooting when a tripod is allowed. The Pentax crop lens (in crop mode on the K-1) when I'm walking around or a tripod is not allowed.

With the FF lens, I mount the camera to the lens. With the crop lens, I mount the lens to the camera.

If I wasn't into landscapery pursuits, after having used the FF system, I'd probably just have switched back to crop. With crop, the IQ is decent enough for most general situations, weighs less, size is less, and it costs a lot less.

Those of you on crop looking forward to FF digital systems (never having used one before) need to consider this aspect I think.

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Last edited by mee; 02-16-2018 at 07:44 PM.

[MadMathMind]

If you were comparing wide angle lenses, you'd be totally right. But in this case, you're really underestimating the additional complexity and elements needed to get that extra 100mm. This is where most of the size and weight come from here.

For comparison, the DA55-300 is fairly simple, with 12 elements in 9 groups. The 120-400? That's got 21 elements in 15 groups. Telephoto lenses are easier to make because the projected image has to be "shortened," not lengthened as in the case of wide-angle lenses. That's a bit easier to do but if the focal length increase is significant, then it becomes a much more complex process optically. Think of it this way: the focal length is the distance from the back of the lens to the focal plane when the lens is set to infinity. An extra 100mm means that image circle is about 4" further behind, or well beyond the back of the camera. That requires more elements to correct. Further, the magnification of 400mm vs. 300mm is significant and requires a much larger lens even for the same sensor size.

Nikon's 300mm f/2.8 lens is 10.5 in long and weighs 102.3 oz
Nikon's 400mm f/2.8 lens is 14.09 in long and weighs 134 oz (almost 2 pounds more!) and is 2" greater in front element diameter

Nikon's 300mm f/4 lens is 8.8in long and weighs about 50oz
Nikon's 500mm f/4 lens is 15.2in long and weighs over 109oz

So it's not just APS-C vs. FF. In this case, it's really about the focal length difference. It makes a huge difference as you start to move into the super telephoto lenses.

For a more accurate comparison of focal lengths vs. formats, consider the Pentax FA 100-300. This lens is fairly small and while larger than the DA55-300, it's only about 600g vs. the DA's 450g. There's a difference but it's not a huge world. The FA is not a terribly good lens, of course, but the DA isn't considered a pinnacle either. But this does show you that it's far more about the extra 100mm than anything else.

Now, you can argue that 300mm APS-C and 400mm FF are equivalent because of "reach" but this is a bit of a misnomer because at full frame utilization, you're getting 24MP on APS-C and 36MP on FF, a huge, huge difference in resolution. It's just hard to compare the two because the pixel densities are so different.

[mee]

I'm not underestimating anything.. I'm showing a physical example of the differences between a comparable FF zoom and an APS-C zoom.

You seem to think it is a versus. It isn't a versus. You misread if you thought it was a versus. Stop thinking it is a battle you need to fight!

Yet size and weight are aspects I probably should have weighed (no pun intended) more before jumping into FF. I don't care the technical whys, just the physical reality. We have enough technical speak on the forums as is. What the forums can't really fully explain (again because its text only) is the difference in size and the difference in weight between these long teles.

[D1N0]

an equivalent lens on full frame to the 55-300 would be a 82-450 F5.6-8.4

[ccc_]

I've read this a couple of times and i'm confused

are you comparing the lenses on the basis of functional equivalence?

[mee]

an equivalent lens on full frame to the 55-300 would be a 82-450 F5.6-8.4

Bingo! And the 120-400mm closely matches that. At least as close as is made.. You or I cannot buy an 82.5-450 f/5.6-8.4 lens. We can buy a 120-400 f/4.5-5.6 though.

I'm discussing within the bounds of what is available.

[Trickortreat]

I can relate somehow to this. I've jumped the ship from Nikon FF to Pentax APS-C DSLR. Now I have a K-S1, and sold all of my zoom lenses. I like that Pentax cherished for their APS-C only shooters and hope that they will continue to make APS-C only lenses and not force their users to use larger FF ones.

[D1N0]

A lens like that could be made though. Nobody does, because size and weight is not an issue for people who want the best possible quality. You might as well shoot aps-c then. So full frame is not for everybody. This also is only an issue for long focal lengths.

[mee]

A lens like that could be made though. Nobody does, because size and weight is not an issue for people who want the best possible quality. You might as well shoot aps-c then. So full frame is not for everybody. This also is only an issue for long focal lengths.

Those are exactly my points. Thank you!

Full frame isn't the end all be all it is often hyped to be online. There are advantages and there are disadvantages. And all aspects should be considered when buying into a new camera system. Which was the other main point of my thread here.. to give people considering FF things to think on before spending all the money and committing.

Are you (not you D1n0 specifically) really willing to deal with the size and weight of long teles ? That's a question to ask ourselves. Hand holding a crop tele such as the 55-300 is super easy. Hand holding a 150-450 or 120-400 is not as easy. You'll probably need a sturdy tripod and perhaps a nice gimbal. Think think think before you buy.

I get the feeling you, personally, online "Discussion" has to be a debate on ff vs aps-c.. right vs wrong. 2 enter, 1 leaves. The thunderdome..

But that isn't the discussion here specifically. Because FF is excellent and APS-C is excellent. We can enjoy each for what they offer. I'm simply throwing out an aspect to consider when considering buying FF with a visual aid. Relax!

[mechmike10]

Actually, another way of looking at this is the 120-400 is a 180-600 in crop mode, so your what your really comparing is what you need to get a specific focal length equivalent in crop vs full frame. If you are satisfied with 450mm equivalent, then a 300mm (long end) zoom or a 300mm prime in APS-C is all you need. If you want even more reach, then you need more focal length, which is going to get bigger/heavier than the 55-300. Since there are no such lenses made for APS-C, you are looking at a full frame lens. If you compare an inexpensive full frame 70-300 (eg. the Sigma 70-300 f4-5.6 for Pentax) with the 55-300, which is pretty close in focal length, it is slightly longer and heavier, but not by much.

[Rondec]

In general, I still use my K3 for telephoto purposes. Mainly because I don't own a 400mm lens and the K3 is probably a better wildlife/birding camera for the casual birder anyway. It has a faster frame rate and I can't get close enough to most birds so that I lose the benefit of all the extra pixels the K-1 has because I'm cropping to less than APS-C anyway. On the other hand, full frame definitely has an advantage when it comes to wide angles.

That said, it is important to note that you do need to adjust apertures to make a valid comparison. A 16-50 f2.8 on APS-C is not the same as a 24-70 f2.8 on full frame -- they just give similar fields of view. Most of the lenses that are so small on APS-C are small because they have relatively slow apertures compared to the full frame versions. I think it would be nice if Pentax made f4 full frame versions of their standard and 70-200 lenses, but so far those aren't available.

[dadipentak]

Those of you on crop looking forward to FF digital systems (never having used one before) need to consider this aspect I think.

Absolutely! Especially those of us who have gotten old & frail waiting for the Pentax FF.

Like Rondec, I use my K-3 for telephoto (also hiking and most of my wander-about shooting.)

I do like my K-1 but tend to pretty selective in it's use and think twice about lugging it around.

[surfar]

What about 55/300 with a 1.4x TC= 77/420 f5.6-8.4....that newish PLM might go pretty well?

[mee]

What about 55/300 with a 1.4x TC= 77/420 f5.6-8.4....that newish PLM might go pretty well?

On crop it sure would.

[Trickortreat]

Full frame isn't the end all be all it is often hyped to be online.

Exactly my thoughts. I love my APS-C gear and DA lenses. Every single bit of them. And wouldnt stick a FA lens to my camera even if they paid me money to do it