Aerial photos from helicopter

[john_dixon5]

I have a Mamiya 645e (standard 80mm lens) and have used it with good results

taking pictures from a helicopter of construction sites. One of the problems is

some of the sites are small, and not been able to go lower than 1500 ft, I dont

fill the frame with the 80mm lens. I am not a professional, just do this for

fun and to help out the place where I work. A zoom lens is out of the question,

too expension. Forgive me if this sounds like a stupid question, but would a 2x

teleconvertor be any use, ie, bring the objects in to fill the frame, also,

would a 160mm telephoto lens be any use? Does a 160mm telephoto mean a fixed

160mm, and is that twice the 'zoom' of my standard 80mm lens?

 

Thanks

 

 

John

[User_502260]

When it comes to medium format equipment a teleconverter can sometimes be more expensive than a prime lens. There are many 150mm Mamiya lenses for your 645e available and prices are very reasonable. The fastest ones have a maximum aperture of f/2.8. A 2X teleconverter with your standard 80/2.8 lens will give you a 160/5.6. This will be much more difficult to focus and not as sharp as a 150. I have had good results using a 2X teleconverter with the 80/2.8 S Zenzanon on my SQ-A but the view through the finder is not very bright.

[john_dixon5]

Thanks Jeff, it sounds like a 150mm lens is the way to go then.

I will have to check Ebay.

 

John

[CosteaM]

John, check KEH as well, you will be surprised. I found cheaper stuff there compared to evilbay. It comes with warranty and you always know that items are as described.

[john_dixon5]

Thanks Mihai,

 

I am in England, no KEH here, but I get your point.

 

John

[radu_vadan]

KEH does ship overseas... I just ordered a 50 f/2.8 and a WLF for my Bronica a few days ago, and am waiting for it to arrive. I am in Romania by the way.

[radu_vadan]

Also, KEH is currently listing a few 210 f/4 somewhere around $100 (one hundred, no typo). They also have some longer lenses. Consider the fact that a 150 is not all that much longer than your 80mm.

[john_dixon5]

When you say the 150mm is not much longer than an 80mm lens, how is this calculated? (I'm a novice) I was thinking that it would bring objects twice as close, is this not the case?

 

Thanks

 

John

[q.g._de_bakker]

John,<br><br>It is correct. Well, nearly.<br>Though it is currently disputed in another thread (wrongly), the ratio of focal lenghts defines the ratio of fields of view and angles of view.<br>The 150 mm being nearly twice as long as the 80 mm, it images things nearly twice as large, having a field of view that is nearly twice as small.

[ondebanks]

John,

 

Actually, if Q.G. is referring to the "New Very Wide Angle Lense for Mamiya 645 - 28mm!!" thread, then *he* is the one who is wrong. [Read my most recent posting there, where I gave the correct formula...]

 

But the degree of error in his flawed formula shrinks rapidly as one moves from the wideangle regime into the telephoto regime - so what he told you is _approximately_ right.

 

The accurate version is this: a 150mm lens magnifies 1.8x more than your standard 80mm lens; a 210mm lens magnifies 2.5x more than your 80mm lens.

 

On a budget, you can choose between the 150mm f3.5 or 210mm f4 lenses. Both are very good. From a moving helicopter, you might find the 150mm that little bit easier to focus and hold steady. On ebay, a major dealer called Shutterblade [- usual disclaimers apply, no personal connection to them etc. -] regularly offers theses lenses for a steal (yes, even their Buy-it-now price beats most open-auction prices). I've had stuff shipped by them to Ireland without a hitch. The favourable exchange rate versus the weak dollar makes up for the shipping cost.

 

One last thing - look for the versions of these lenses labelled "N": they are the newer type; more plasticky but lighter and with better multicoating.

 

Ray

[lightminer]

While they are a little pricey (you can rent them it seems) these can help with ariel photos.

 

http://www.ken-lab.com/

 

And, yeah, definitely don't get the 2X thing because of what it does to minimum f-stop PLUS the fact that it won't work with the 80mm lense from what I understand, only the 150 and over because of protruding glass that needs somewhere to fit into.

[john_dixon5]

Thanks everyone for your helpfull information, now I have a better idea of what I need.

 

John

[hans_ched]

One question to KEH - when they ship to Europe, you do have to pay customs, don't you?

[radu_vadan]

Yes, you have to play customs AND VAT!

[ondebanks]

I find that lesser-valued packages pass through to me without attracting the attention of customs officials. $200 seems to be the point where they can be bothered to tax them. Let's hear it for bureaucratic inefficiency.