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Photography Question
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ghporter
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Oct 28, 2022, 05:12 PM
 
I’m not super strong on how focal length affects some factors, thus my question.

I’m photographing old negatives that turned up a short time ago to both preserve the images and make the images accessible. Things like pictures from our son’s infancy, our (early) vacations, etc. Some of them are super precious others just wonderful memories.

My DSLR’s (APS-C sensor) lens has an 18-55mm lens, but at 55mm, it just doesn’t cut getting a good shot of 35mm negatives.

I have a set of three simple extensions that can increase the focal length by 18*, 22*, or 31mm, or any combination. I can get good images with either the middle or longest extensions, but I’m not sure whether I’m trading off anything in the process. I’d appreciate any guidance on the optics and aesthetics involved.

*I’m not 100% sure of the actual lengths of the shorter two extensions, but I actually read the marking on the 31mm extension just a little bit ago…

Glenn -----OTR/L, MOT, Tx
     
subego
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Oct 28, 2022, 05:35 PM
 
FWIU, the only effect is it less light gets to the sensor. How you compensate for that will have an effect.
     
ghporter  (op)
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Oct 28, 2022, 06:34 PM
 
OK, that helps a lot.

I’m using my Canon EOS Digital Rebel XTi (not exactly a spring chicken of cameras, but it’s what I have). Per advice/instruction on a variety of photography sites, I have the camera set to “Aperture Value” mode - I set the f-stop and let the camera figure out how long the exposure should be. So far great exposure results with this setup.

Side note: how did I ever get along without a remote shutter release? Anyway…

If I can fill the camera’s entire frame with the negative’s image with either the middle or longest extension, then one thing to consider is how the longest extension reduces the amount of light getting to the sensor - am I on track?

I’ve settled on an LED light table/box that seems to be super even, and both bright and cleanly white - it produces plenty of light at a consistent level. And I’ve gotten great images using it. Since the camera is locked down on a real photography copy stand (an exceptionally great investment) I’m not really “worried” about exposure time, but longer exposures also introduce the possibility of anything from me sneezing to a seismic event introducing shake. Not what I want.

I’m going back to the start with the extensions. I don’t think I tried the shortest extension; maybe I can fill the sensor with a film image with a 73mm, and get more light to the sensor in the process. I’ll go back to my “test negative,” a picture I took of a kitten on my wife’s lap back in 1986 or ‘87, and do a real comparison of clarity and saturation and everything with the different extensions.

Glenn -----OTR/L, MOT, Tx
     
ghporter  (op)
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Oct 28, 2022, 06:37 PM
 
I should add that I’m also safely preserving the negatives themselves in archive-quality sleeves as I’m sorting through them.

I want to get “the perfect scan” on the first try, but I’m also OK with learning a thing or three and going back to an image to do better than in an earlier try, so having my negatives organized and protected means I can do that safely.

Glenn -----OTR/L, MOT, Tx
     
reader50
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Oct 28, 2022, 06:43 PM
 
Did you attempt scanning them first? I scanned our family positives a few years ago, using a flatbed. But most of our negatives are non-35mm, so don't work with dedicated negative scanners.

Scanning negatives using a flatbed was possible, but took way too much work. I'd rejected photographing them at the time, due to concerns over low pixel count and possible barrel distortion. I ended up setting our negatives aside until some unspecified future effort. Now I'm warming to the idea of just shooting them.
     
subego
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Oct 28, 2022, 06:54 PM
 
Originally Posted by ghporter View Post
If I can fill the camera’s entire frame with the negative’s image with either the middle or longest extension, then one thing to consider is how the longest extension reduces the amount of light getting to the sensor - am I on track?
You got it! If you can get an equally sharp image out of the middle extension and also still get full coverage, that’s the one to use. It won’t cut down on the light as much.

What f/stop are you setting the aperture to and what kind of shutter speeds is it giving you? Same question with ISO, which I think it might be playing with too.

I’m a manual guy.


P.S. Lighting sounds ideal!
     
ghporter  (op)
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Oct 29, 2022, 11:45 AM
 
reader, I've spent quite a bit of time using my flatbed scanner to digitize prints. There are some hoops to jump through to get good results.

Like for some reason I can't get my iMac to tell the scanner to use its highest resolution, 1200dpi interpolated. But the scan app on my Linux machine, Simple Scan, will happily use that resolution. Unfortunately that app doesn't manage colors well, so I have to move the images to my iMac and use Preview to touch up colors and such because (as much as I like it) GIMP on any platform is too clunky for that task.

On the other hand, I've located the negatives for many of the more important photos that I've scanned prints of. I'll be able to scan those negatives and get higher resolution - and higher fidelity to the original - than is possible with any scanner I have access to.

subego, I did that test with each extension tube, and it clearly demonstrated how much light each extension "cost" me. I really, REALLY like free software that does what it says it will. It's even better when that free software does more than I could have asked. It's called RawTherapee, and I got it primarily because it natively handles Canon's raw file format (CR2). But it also automates correcting negative to positive, and doing all sorts of other image tweaks, including both 90 degree and free-form rotations.

Here are my test negative images:

This is with the 31mm (longest) extension (55mm + 31mm actual focal length), f8, 1/2 second exposure.

This is with the 21mm (middle) extension (55mm + 21 mm actual focal length), f8, 1/3 second exposure. The focus is off in this image, but that's on me.

This is with the 13mm, shortest extension (55mm + 13mm actual focal length), f8, 1/5 second exposure. It feels like this image is more vivid than the other two, even though the only difference is the optics.

Since I don't see any benefit in using any more extension than needed, I'm sticking with the shortest one. I'm also going to see if my initial decision that 55mm wasn't macro enough was valid, or due to something else, like lack of experience with the process, or hardware limitations. My earliest experimentation was done initially using a tripod to support the camera, which really limited how I could position the camera. Since I've moved up to a real copy stand, that may change things.

Also, the shorter the extension I used, the closer I could get the lens to the negative. This made it easier to block extraneous light. Unwanted, non-image light causes problems with the photographed image. A definite plus.

Glenn -----OTR/L, MOT, Tx
     
subego
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Oct 29, 2022, 12:11 PM
 
To me, the longest extension looks sharpest.
     
reader50
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Oct 29, 2022, 12:43 PM
 
I'm happy with how my positive scans came out. It's only the negatives that remain to be scanned someday.

Originally Posted by ghporter View Post
Like for some reason I can't get my iMac to tell the scanner to use its highest resolution, 1200dpi interpolated.
Don't bother with that setting. "Interpolated" = they scan at a lower resolution, then the scan software scales it up. It's probably scanning at 600, and your photo software of choice can scale upwards at least as well as the scanner software. In all cases, interpolation doesn't add detail. Just file size.

600dpi is often overkill because print processes (especially older ones) can't generate detail that high. example: newsprint, especially newsprint photos.

My positive scans were done at 600. The exceptions where you go higher would be a positive transparency. ie - a slide. Scan those like you would a negative, with a camera, or a scanner than can go to crazy high dpi without interpolation.

Originally Posted by ghporter View Post
Also, the shorter the extension I used, the closer I could get the lens to the negative. This made it easier to block extraneous light. Unwanted, non-image light causes problems with the photographed image.
Suggest making a mask, using black art paper. With a cutout slightly larger than the negative.
     
subego
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Oct 29, 2022, 12:44 PM
 
Originally Posted by subego View Post
To me, the longest extension looks sharpest.
Longest:




Shortest:




Not a massive difference, but perceptible.

I can’t say if that’s because of the extension or because you nailed the focus better.
     
ghporter  (op)
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Nov 1, 2022, 01:34 PM
 
I agree that the samples show sharper focus with the longer exposure than the shortest, but I also agree that it could simply be that I focused the longer exposure shot better. I’ve addressed that - please read on.

In the past two days I’ve made some changes to my setup. One was setting up “guides” made from matboard on my light source (an A4-sized tracing light box), that lets me position the film carrier (which holds the negative strip) more consistently. Less farting around with getting the image centered for the camera meant I could pay more attention to focusing.

The second was that I bought a new camera. My Rebel XTi (released in 2006) was quite elderly, but seemed to do the job well. Except that I had always thought it had a 12MP sensor. That’s important because 12MP is larger than the customary definition of a 35mm film frame’s pixel density of 10MP. But I was wrong; it’s sensor is only 10.1MP, which gives me zero “slop” for image capture.

The new camera is not a just released model. It’s a Rebel T7, released in 2018. But it has a 24MP sensor, which lets me get all of the negative image plus a little and still retain ALL the data from the image.

It also has an LCD display that makes it MUCH easier to frame the negative than the viewfinder on the XTi. Plus the LCD has a mode that lets you zoom in on the image to verify your focus. Enough zoom to let you see the grain in the negative. If you can focus on the grain, you have nailed the focus.

Reader, I will have to make some masks. The film carrier holds the negative nicely, but its opening is big enough for almost two frames. And many of my negatives have images I need to capture that are at the very end of the strip, so there’s lots of light getting around the image and changing how the camera meters the whole shot. Fortunately, I bought a huge chunk of matboard a while back, and cutting these masks won’t be very challenging.

If I get the time today, I’ll repeat that test image with the new camera, plus the other refinements I’ve made, and post it here.

Glenn -----OTR/L, MOT, Tx
     
subego
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Nov 1, 2022, 02:44 PM
 
Well, sheeeeit.

I’ve got a 5Dmk3 body I can lend you if you’re interested.


Sorry it didn’t occur to me earlier!
     
MacNNFamous
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Nov 1, 2022, 05:54 PM
 
I used a USB powered film scanner, worked great but had to boot into windows to use it.
     
ghporter  (op)
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Nov 1, 2022, 07:32 PM
 
subego, "it was time" for the XTi to be replaced. And with all I really need and want to do with all of these negatives (I don't even have an idea of how many frames there are to assess, digitize and archive), I really needed a new camera. And my lovely wife said "just go get the camera you need." So I did.

Famous, I'd used the usually robust scanner of my all-in-one printer to capture prints, and it did OK. But capturing negatives would mean buying an Epson negative scanner at the very least (they make the closest thing to a consumer/prosumer scanner with native negative capability). And while there are a lot of people who swear by these scanners, a lot of pros say their scans come out muddy or flat. So I went this route.

Anyway, here's the test image captured with the new camera:


I literally did zoom in enough to see the grain in the image of the kitty's eye. I'm floored by how sharp this camera can focus.

As an added bonus, all of Canon's software that I couldn't get to work with my XTi works with the T7. Different versions, of course, but it all works. I can sit at my laptop next to the camera stand, control the camera from the laptop, see the results and post-process (only negative to positive with the above image) on the laptop. Fantastic. And less back strain from peering over the top of the camera to frame and adjust focus, too!

Glenn -----OTR/L, MOT, Tx
     
reader50
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Nov 1, 2022, 11:44 PM
 
Originally Posted by ghporter View Post
But capturing negatives would mean buying an Epson negative scanner at the very least (they make the closest thing to a consumer/prosumer scanner with native negative capability). And while there are a lot of people who swear by these scanners, a lot of pros say their scans come out muddy or flat.
I have an Epson Perfection 3170 photo scanner (flatbed). It's excellent for scanning prints. But for negatives, I ended up giving up. At the time, anyway.

The scanner does indeed go to high enough dpi for negative scanning. And it includes adapter trays to hold negatives, with a backlight built into the lid. But when I tried, I found the focus plane is not where the adapter tray sits. The focus plane was always at the surface of the glass.

So the glass had to be super-clean, between every scan. And the negatives had to sit on the glass. This is not ideal, making it easy to trap dust between negative and glass. Which even compressed air would not reach. Also, it was possible to put fine scratches on a negative.

The number of problems to work around were just too much for scanning a bunch of negatives with the Perfection. If you do a single negative rarely, then it's a viable solution. And the positive print scans are great.

Whenever I try negatives again, I'll do it your way, Glenn. I own a Repel T2i with 18 megapixels. Plus a few different lenses. Just need to buy a light table and overhead camera mount.
     
subego
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Nov 2, 2022, 01:34 AM
 
Originally Posted by ghporter View Post
subego, "it was time" for the XTi to be replaced. And with all I really need and want to do with all of these negatives (I don't even have an idea of how many frames there are to assess, digitize and archive), I really needed a new camera. And my lovely wife said "just go get the camera you need." So I did.


I was thinking without looking the 5D might give you a higher resolution but the T7 beats it, so you’re all good!
     
ghporter  (op)
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Nov 2, 2022, 09:04 PM
 
For a non-pro class camera, the T7 really knocks it out of the park for everything I need and want it to do. It’s also a tad bit lighter (body only) than the XTi, which will help when I use it for original photography.

In January, my wife and I are going to one of the most spectacular of the national parks: Big Bend. And with all the spectacle the park offers, we have fallen in love with the Chisos Mountains. Here’s one of the reasons:


So needless to say, I’m going to be photographing the snot out of the park.

Back on topic, I’ve been tinkering with combinations of macro and distance from subject. I’ve found a fairly good sweet spot that captures all of the image plus some, but not too much extra. When a negative is at the end of a film strip, the light source can wash out the image, and cause the metering to go wonky. Getting in close enough to get the whole image plus the border around it pretty much solves that problem.

Glenn -----OTR/L, MOT, Tx
     
subego
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Nov 2, 2022, 09:09 PM
 
Originally Posted by ghporter View Post
For a non-pro class camera…
My experience in general is it’s the glass that will matter more.
     
Brien
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Nov 2, 2022, 11:44 PM
 
Yep. L series or bust.
     
ghporter  (op)
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Nov 6, 2022, 06:06 PM
 
So far, Canon’s EF lenses have been very nice to me. If I were capturing microfilm, I might need to upgrade the glass, but negatives and slides should be fine with my lenses.

Both of my Canon DSLRs (the XTi and the new T7) came with 18-55mm lenses. Both of these lenses have autofocus, but the new one has image stabilization, too. It also has a better widest f-stop. I can’t recall the numbers at a moment, but it’s like f8 on the older one and f5.6 on the newer one. I’m liking it a lot.

Glenn -----OTR/L, MOT, Tx
     
subego
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Nov 6, 2022, 09:59 PM
 
In practical terms, the big allure of the Ls is the edge of their envelope versus non-L offerings.

My personal favorite is the 70-200. Compared to a non-L, I can get up to 4 extra stops out of it before I’m underexposing a shot.
     
reader50
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Nov 6, 2022, 10:17 PM
 
Originally Posted by ghporter View Post
If I were capturing microfilm, I might need to upgrade the glass, but negatives and slides should be fine with my lenses.
You're limiting your career choices, Glenn. For any decent spying work, you need microfilm capability. How else will you sneak those documents out of the DMV that they never want publicized?
     
ghporter  (op)
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Nov 6, 2022, 10:42 PM
 
Way back in the Dim Times, I had to, on a routine basis, research part and stock numbers with data on microfiche, and it was a major PITA. But frankly, it’s much friendlier than microfilm; at least microfiche are individual pages, not rolls of film…. And as far as I know, none of the photographs I’m going to be digitizing, archiving, and preserving depends on text in the image. Good thing, too.

However, there’s a Kickstarter promotion about to kick off that is two transparent test cards that meet ISO12233 or USAF1951 standards for testing resolution. You can get one, the other, or both. I’m on the list to hear when the project goes live, and I’m buying both cards. I don’t “need” anything to verify I’m getting the focus and framing I want with these negatives, but it’s a very geeky thing to be able to put numbers to how well a photographic setup resolves detail…

Glenn -----OTR/L, MOT, Tx
     
   
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