26 replies to this topic

[CWIWelding]

So from what i've read and the comments from Merco which I've just researched and can now see the problem, the Samyang/Rikonon will not do the task... Hmmm

 

So it definitely means i have to get close anyway then, which is why i was looking at the welding lens option in the first place, just in case.  I do not however want to get too close as it would be more of problem for the welder... so 18 -24" away.  Do you think the Nikon Micro-NIKKOR 105mm f/2.8 Lens would be a better option Merco?  Its a 1:2 natively but i could get a 1:1 ratio with the PN-11 adapter.

 

Being in the trade and being in education i attend a lot of seminars/shows around the country, Ive seen the ccd camera's fitted in many welding training cells, IMHO i've yet to see one give a really sharp image with relatively smooth video, as i said... yet to see, that doesnt mean they havent gotten there yet lol

[Merco_61]

At 1/1.5, you would have a working distance of just under a foot with the Ais version, even shorter with the current AF-S VR. The 200 would be about a foot too, as the lens is so long in itself. A D3xxx or 5xxx body won't meter and of course not AF with the old manual lens, but exposure will be trial-and error anyway under such extreme circumstances. . When you read specifications, the minimum focus distance quoted is to the sensor plane, not to the front element. I wonder if a CX body like the Nikon 1 J4 with an F-adapter wouldn't be a better choice than a DX one.

[CWIWelding]

Sorry, sleep overtook me at 4am this morning lol

 

I do see what you are on about Merco, and to show how much of a noob i am, I just found out how to alter the F Stop, and I'm serious there... yes I am that much of a novice

 

Up until now I have always had camera's that were automatic, point and shoot.  I had no idea what i was missing

 

So I have a question regarding the x1, x2, x4 close up macro lenses shown below

 

 

if i add a lens to magnify the image... why does the minimum focus length shorten?  it is measured from the sensor right?...  i mean that length doesn't change. and just screwing one of these in doesn't extend the lens, it just screws in the end.  Does having an additional element, albeit a screw in closeup macro lens like one of these technically "move out" the last optical element? If I have this right, and from the video I've seen it seems to be, you can creep in a little per lens you add, just a few millimeters, but basically its just the image that's magnified right? which in turn would mean that i could feasibly move the camera back a little and retain the same image size with the close ups on... that i had with just the native lens.  Is that correct? at least in theory? I know that they are made to be able to get in closer, but if the effect of the lens also means magnification of the image it should also mean i can move back...

 

I know we are talking inches here, but in this case... size (distance) does matter lol

 

I would like to thank all of you for the comments posted so far, which I am extremely grateful for... they have helped me understand this problem a whole lot better, and after countless hours of research I can clearly see what Merco is saying, that using a super telephoto lens won't achieve what I need. Other research has also shown me that extension tubes would be self defeating as any benefit i would get in magnification would be outweighed by the lens assembly increasing in length and shortening the gap between the outer element of the lens and the object (getting closer).

 

My biggest concern now, as I am reserved to the fact that super telephoto lenses just wont work for what i want... is that i concentrate on shielding the camera knowing its going to have to get close to the weld, while still maintaining enough room so that it doesn't impede the welder performing the actual weld.  I need it back just a little to give him room to work.

[CWIWelding]

OK, back to the drawing board, the whole adding the close up lenses idea wont work... in fact the whole idea of magnification after the lens seems self defeating as the amount I would gain by adding a close up lens is taken away by the decreased range at which I could use them... Or at least it seems that way.

 

Can anyone tell me if my numbers are correct here?

 

Close up or Macro lens filters are measured in a Diopter number, these lenses alter the maximum and minimum focal length when fitted on a lens.  The diopter value ( +1, +2 etc.) is a number which is used in a formula, which tells you the power, or focal length, of a lens. One diopter is the reciprocal of one meter of focal length ... or, in basic terms…  ( 1 ÷ (focal length in meters)) 

 

So… 

- Your +1 lens is 1 diopter, or 1/1 meters, or 1,000mm focal length

- Your +2 lens is 2 diopters, or 1/2 meters, or 500mm focal length

- Your +4 lens is 4 diopters, or 1/4 meters, or 250mm focal length

- Your +10 lens is 10 diopters, or 1/10 meters, or 100mm focal length

 

Already this is telling me that I could only add a few diopters of power to benefit from the lens filters... as an increase in diopter values mean that the maximum focal length is decreasing and even at +2 diopters (very little magnification) I am already inside 1 1/2 feet from the target to the sensor...

 

Let’s say, for instance, that I want to use a +1 attachment on a 50mm prime lens that normally focuses from infinity to 0.5 meters. At infinity, the optical distance from the lens to the film or sensor is equal to its focal length – in this case 50mm, or 0.05 meters, or 20 diopters.  The focus movement that brings the lens down to 0.5 meters is equivalent to (1/0.5), or 2 Diopters of added power.  If I now add another +1 close-up lens to the system, we have a total of 3 Diopters of focusing power when the lens is set at its closest focus limit.  So the lens and the +1 = 3 Diopters or 1/3 of a meter which = 333mm or 13 1/8" 

 

Upping that by another diopter value, adding the +2 instead of the +1 would therefore bring down my max range to 250mm or about 9 7/8"... and that's just with a plus 2!!!  The magnification would be minimal and I'm losing max focal length hand over fist.

 

I'm just waiting for Merco to say i told you so lol

[dem]

... plastic (what the lens body is made of) has a melting point of under 400 degrees F, hence the reference to the picaso melting clock

It is Salvador Dali.

Have you considered small sensor cameras with large zoom, e.g. a bridge camera P900 or some Canon or Sony video camcorder?

[CWIWelding]

Very true, it was Dali...

 

The whole small sensor subject was brought up by Merco... I've even had some comments from others privately mentioning the go cam series, I think mainly because of the size of them the new adapters they have for zoom lenses and the small sensor

[TBonz]

I think Merco's idea of a Nikon 1 series camera is definitely something to look into...The FT1 adapter would allow you to use the Nikkor lenses from your DSLR on the Nikon 1 body as well as any of the Nikon 1 lenses that might work.  I have used both the Nikon 1 V2 and V3 and have been pretty happy with the results.  They are also a smaller body which might make it easier to enclose when you bring it in closer.