Rifle Scopes Why so much variation in scope length??

[ego235]

Can anyone elaborate a little about why rifle scopes come in so many different lengths? I understand generally for a specific model of scope, the more magnification, the longer the scope. Leupold MK4 4.5-14 is shorter than their 6-24. S&B PMII 4-16 is shorter than their 5-25. That is pretty obvious.

However when looking at magnification ranges of different manufacturers such as my Leupold MK6 3.5-18x44 is short and stubby, almost 2 inches shorter than my Premier 3-15x50 but with more magnification. But my new vortex 2.5-10x32 feels quite long, in fact it is 1" longer than my MK6...and it only has 10x top end.

I see recently more and more companies are starting to come out with new lines of more compact, shorter scopes than traditionally made in their magnification range. Do the shorter scopes have any inherent disadvantages compared to their longer cousins?

I'm only guessing here but does a shorter scope have shorter focal distance, ie. more hunting around with the parallax knob when shooting at targets of varying distances? Is there any improvement in overall clarity and picture with a longer scope? What about field of view? I tried to search for some of this information online from different scope maker's websites but much of it seems inconclusive.

Maybe I have it completely wrong and it is kind of like laptops, where price is the main driver of building thinner and lighter, they can still have the exact same specs. Somebody please weigh in.

Does no one else ever wonder why a March 3-24x42 is only 12.3" while a similar magnification USO 5-25x58 is 18" long?

 

[George63]

physics requires length in a scope for generous depth of field (how much depth is in focus at one time ) - the march is tuned for bench rest so only needs sharp focus at the distance being engaged ( bench rest classes limit weight so you want maximum scope performance per ounce ) - the USO would be tuned for field use/ target detection where a generous field of view is wanted and weight is less of an issue - no doubt there are other factors involved

 

[ego235]

Ah thanks George, that was what I thought too, except I used the wrong term, focal distance instead of depth of field. Now maybe this is not a fair comparison, but how come when I compare my Premier Heritage 5-25x56mm to my Swarovski 25-50x65mm spotting scope when both are at 25x, the Premier has WAY greater depth of field. I only need to adjust maybe every 15-25 yards I'm moving or so upto about 300 and after that its all the same. Yet with the spotting scope every couple of feet I need to adjust the focus otherwise it is completely blurry. They're almost identical in length.

 

[rchman]

I think it has to do with for a given magnification, it requires increasingly more complex designs to make the scope shorter.