Speed Graphic with 178m f2.5 Aero Ektar lens + Maco IR820 AURA film

[engelgrafik]

OK, I'm about to start undertaking my photo project and before I start

experimenting, I'm hoping to get some folks to hand me down some good advice and

suggestions.

 

I have a large format 4x5 Speed Graphic with a custom-mounted huge lens, the

178mm Kodak Aero Ektar f2.5 aerial lens. I love the classic bokeh this lens

uses, it will be perfect for a personal photo project I'm working on.

 

My main question is this: at 178mm and opened up to f2.5, do I still need to

worry about focusing issues if I'm only using a Red #29 filter (or a large

processed empty sheet of 4x5 E6 film, as I've been told works excellently as a #29)?

 

I did a calculation on DOF with one of the online calculators. At f2.5, depth of

field is REALLY shallow with objects that are super close up... talking inches

and even less than an inch in some cases. My subjects will be probably around 10

feet away. At that distance, depth of field is only HALF a foot!

 

So as you can see, any recommendations on adjusting focus would be great. I

don't know how much "red" the #29 lets through but if it lets through 50% red,

then I'm assuming I should be just fine, and the IR and "AURA" attributes of the

film will contribute to the glowy dreamy effect that I'm looking for, even if

the IR part of the spectrum is a tad out of focus?

 

However, let's say I was focusing for IR, would I be rolling the bellows BACK or

FORWARD after focusing on ground-glass? With my 35mm and medium format lenses, I

THINK I turn "closer" to ajust for IR film if I remember correctly, but I can't

remember. So if it's closer, then I think I push the bellows FORWARD and OUT,

correct? Or is it the opposite? I don't know why I'm so confused. LOL

[frank.schifano]

I can't tell you how much correction you'll need. There are probably a few folks here who know the formula for that. Adjust for the focus shift of infrared light by setting the focus a little bit before, or in front of, the ideal plane of focus. To do that, increase the distance between the lens and film plane by extending the bellows. It works the same way any other lens on any other camera. Why would you be confused? Don't forget to adjust your exposure to compensate for bellows extension when doing closeups. See here for some tips on how to do that: http://www.largeformatphotography.info/bellows-factor.html

[oskar_ojala]

Hard to say, some lenses have bigger focus shifts than others. I've only shot Maco IR with a red filter in 35 mm, for strong IR there was a slight out-of-focus effect in closeups. In medium format I've used black IR filters, where a correction is definitely needed. On a gut feeling, I would say that a little bit of correction in IR heavy light is needed since the DOF is very shallow with you combinaton. I would recommendto doing a few test shots.

[kelly_flanigan1]

The IR focus is a tad longer than the visual IR focus. Some folks use a 1/4 percent movement as a trial first guess. I know from using the Aero Ektar on my phase one scan back than there is a real shift from visual to IR; but really have not measured it. Just do some tests; photograph a ruler at an angle; see the shift if any.

[kelly_flanigan1]

The focus shift from visual to IR depends on the "color correction" of the lens design. The aero ektar is a well corrected lens; but it still is not perfect.

[engelgrafik]

One thing I'm thinking is that since 1/3 of depth of field is in front of a focused object, and therefore if I focus closer, the other 2/3 of depth of field should give more focus latitude to the object I want in focus. So "focus closer" makes sense. And yes, I will definitely bracket. I think I'll be shooting several sheets per shot just to make sure.

[profhlynnjones]

You extend the bellows but the amount is miniscule! The old literature used to tell us that the extension was 1/10th of 1% of the focal length for IR. In your case that would be a tiny amount, less than 1 mm.

 

Stopping down a bit should take care of it easily. By the way, I have one of these lenses mounted in shutter for press or VC use and another mounted for Nikon SLR. These are good lenses although they were made for Fairchild 4x5 aerial cameras by Kodak and were 5 element Pentac/Heliar type lenses at which Kodak was very good. The WWII price to the government in the 40's was about $800, or about 1/3rd more than the cost of a new 4 door sedan!

 

This lens is superb for portraits shooting wide open taking advantage of the extremly shallow depth of field under those conditions.

 

Lynn

[oskar_ojala]

My experience has been that the extension is a bit more than 0.1% of the focal length, but as I said, it is lens dependent, so it may well be just 0.1% with this lens. However, the additional extension is a function of the current extension, if the extension is 1 mm at infinity, it would be more when approaching life-size. It's been a while since I shot IR in LF, but something around 1 mm for a 178 mm at infinity sounds to be in the ballpark.

[al_kaplan1]

By the 1960's you could buy a "Govt. Surplus" Aero Ektar for $29.50, and I think it was Sterling Howard that sold them in focussing mounts for 35mm cameras for $79.50. That would be about $400 today. The Aero Ektars used a mildly radio active glass in one element which causes them to get kind of yellow with age.

[profhlynnjones]

To Al Kaplan,

 

At Burke & James (where I was once VP and lens bank manager), B&J bought bunches of them from the government for about $20.00 shortly after WWII. I used to sell them in Nikon mount for for $119.00 in the late 60's and about that much in a shutter for LF.

 

The prices you mentioned were common a few decades back (when I was still a grown up photographer) but, seriously, during WWII when I was a teen, the government price for Fairchild and other Aerial cameras was $800.

 

Lynn