francesco_bertelli2

<p>(using a monorail camera) is it possible to shoot form the side of a river, and compose the photo like you were right in the middle of the river?<br>

let me explain: do you know the tecnique of avoiding the reflection of yourself in a mirror by moving on one side and then shifting...?... I was wondering if it can be applied on a different context, like a street or a river or so...</p>

<p>i fixed the parenthesis but ti doesn't work if you use millimeters...it basically works only with your values...weird..</p>

<p>Premise:<br>

what the lens list usually say is the image circle @f22, but they don't say is how the image circle increase or decrease.. there are many occasions when you have particular artistic need and you dont realy care about sharpness or diffraction and you rather use a f5.6 or the opposite a f64...<br>

Question:<br>

there is a formula or a complete list where you can calculate how the image circle increase/decrease when stopping down/up?<br>

that formula would be useful so i can rent/borrow/buy a lens for specific use if I knows if it fits my need before even try the lens on the field...</p>

<p>I reduced your formula to this </p>

 

<p>focalHorizontal = 665 / Math.atan( ( ( c1/c2 * h ) - h ) / 2*d ) </p>

 

<p>and if i use your values<br>

h = 4.125<br />d = 10<br />c1 = 5.625<br />c2 = 2.125<br>

the result is 431.435....that doesnt make sense...</p>

<p><em>note: Math.atan is the javascript command for arctan</em><br /><br /></p>

 

<p>i tried building the funciton in javascirpt but it doesnt work for me...i get weird result even using your values..<br>

if you dont have Excel you can use <cite>docs.<strong>google</strong>.com/<strong>spreadsheet</strong>s</cite> , is free, and you can do the math..</p>

<p>also I dont get if you are using mm or inches or if you are mixing them...</p>

<p>wow, 0.5 error is a great result especially because we know there is no lens 35.5 on the market so we can confirm it was used a 35mm on a 35mm sensor...</p>

<p>James,<br>

just to clarify, the value 24 and 36 are because you think ina 35mm format right? so they could be<br>

s1 and s2 where<br>

s1= height of short side of the frame/sensor<br>

s2= height of long side of the frame/sensor<br>

but again, i dont get where 2400 and 43.27 come from...<br>

also H you meand the height of both objects, auusimg they have equal height<br>

am I right?</p>

<p> </p>

<p>@James: hehehe, sorry.. let's stick with the example of twi buildings/cans/lamposts that have same height...<br>

i we can find the forumla i can build it in javascript and will be avilable for everyone as an online caluclator...<br>

the purpose of that? just curiosity passion for optics and math. enough? ;)</p>

<p>@james: i also dont het what is the value H, what do you mean "actual height". and what about if the two cans have different heights and you know both heights?</p>

<p>thanks</p>

<p>@james: what are those constant values 665.5 and 998.25? where do they come from? can we use them for any other example or just the cans example? <br>

thanks</p>

<p>@James, WOW that was i was talking about... that is the answer!! great!!!</p>

<p>i cant find a Scanner Calibration Target for color negative...am i right? what about scanning Kodak Portra 400nc?<br>

are the Silverfast SE settings enough?<br>

thanks</p>

<p>I have a Epson v700 brand new and my first color Portra 400nc 8x10 sheets to scan.<br>

I tried yesterday my first quick scans but i dont get which setting should I use. I'm using Silverfast SE.<br>

My very first doubt is always, how do I know which are the natural colors? when i shoot outdoor i can't use a <em>GretagMacbeth</em> card... and i don ttrust the pre-setting or maybe should I?<br>

i also noticed those setting and autoexposure create underexposed area whereas using the HDR setting i can record all the details even in the shadows...<br>

he problem using 48bit HDR though is the photo is not inverted, but is scanned AS IS, and when you invert it in PS is completly cyan-ish...so in photshop i have no idea how to fix it in a good way...beside playing around with invert>curves> autocolor etc... but i feel my method is not really the good one because i cant colors in all my negs...<br>

please let me know any advice or website where i can learn more...</p>

 

<p>I just realized today after shooting some negs and unloading the holders back in the orignal package that on friday they sold me film sheets expired one month ago 06/2010. beside the fact i'm going to complain anyway because the price was not discounted ot a special sale...do you think the results are going to be fine?<br>

thanks!</p>

 

<p>thanks guys but my second question is maybe more intriguing:<br>

Is there a way to know which focal has been used in a image, given the distance between two objects, and their height?<br>

see this example found on wikipedia<br /><br /><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Focal_length.jpg/220px-Focal_length.jpg" alt="" width="220" height="439" /><br>

if i knew the two cannisters are 20cm tall, and they are 100cm distant each other...how do I know wich focal length has been used and the distance between the photographer and the object in the foreground? Is a way to calculate it using the ratio between the objects on film?<br>

thanks!</p>

 

<p>that's why i aske dif exist an online calculator!</p>

<p>also i was wondering if its possible to the same math given to buildings, the distance between two buildings, the height of both. the ratio between those two you have an idea of the focal right (comporess perpective or the opposite...)?</p>

<p>There is any software online to calculate the focal length a photographer used, given you know the height of te building and the distance he shot the image, and the camera he uused?<br>

let's assume i have an image of the Empire state building and i know the photographer shoo it from 14st (0.9 miles distance) using a 35mm camera...</p>

<p>what's the formula?</p>

 

<p>@Kelly: that's an interesting option... i might buy a 4x5 since i saw on ebay cameras sold for 200 bucks, and use it as a location survey camera...why not...</p>

<p>Thanks robert, that the answer i needed...obviously i would never expect to find a folding toyo 810 for 200 bucks even if that day no one was on internet...but the brands you gave me sounds interesting and i'm starting my research for it.. thanks</p>

<p>I know the indirect mode, but i dont think i have enough image circle (symmar-s = 337mm@infinity) and i tested shooting the building in front of me i can rise the front and lower the back for a total of 6cm max before see any vingetting...<br>

that's why my very first question...thanks!</p>

<p>thanks Warren, that is the answer i was looking for!</p>

<p>wow $50 sounds interesting....i would love though to find something ready...or someone who can build for me...</p>

<p>yes, sorry my english, but i meant the amount of rise... i dont really need o include the tops of the buildings and i dont want to use a super wide angle, but just wondering if usually you use all the way up of maybe just 1-inch is enough...<br>

would be nice to have an online calculator...maybe exists already...<br>

lens degree coverage | distance from the building | building's height = amount of rise... </p>

<p> </p>

<p>I already have a 8x10, heavy and "professional", a nd with nice lenses, but i wolud have a cheap field camera to go outdoor for location survey and then come back with the "real" camera...<br>

what is the cheapest price i could pay fir a used one on ebay or so, excluding DIY...<br>

i saw some ANSCO on ebay sold for $200...but my concern is they mught need accessories or lensboard impossible to find..?</p>