4 x 5 Transparency Scanning Questions

[doug_meek1]

Hi Everyone.

 

I am still trying to become "digital literate" and have a few

questions regarding having my 4 x 5 color transparencies

professionally scanned by a lab.

 

1. When I take my transparencies to the lab and ask for a scan, will

I always get a drum scan or are there other types of scans of

higher/lesser quality ? Do I need (or even want) to specify drum

scan ?

 

2. Regarding the size of the file, I've read postings where labs

charge more for larger files. How do I mathematically compute the

size file I will need so I know what to request (and pay for)? I

want a 30 x 40 enlargement capability. I've read somewhere that 150

lines/inch will appear sharp, and I've also heard that 300 lines/inch

is the correct figure. Assuming 300 lines per inch, do I simply take

30 x 300 (9000) and multiply it by 40 x 300 (12000) for a result of

108mb ? Does this take into consideration my color requirements (is

this "bit depth")?

 

I just want to be able to go to the lab and tell him with a certainty

the type and size scan that I want without having to be concerned

that I'm being taken advantage of due to ignorance on my part.

Thanks in advance for all of your help .

[georges_pelpel]

I do not know about lab scanning as I have never used them.

I recently got an Epson 2450 that scans 4x5 slides at 2400 dpi. For a 30 x 40

enlargement the math is quite simple: the print requires an 8x enlargement

from the negative (5" x 8 = 40"), that means than your maximum resolution will

be 300 dpi (2400 dpi / 8 = 300 dpi) which is the recommended resolution for a

good print.

With the Epson 2450 using the best quality scanning you will end up with

scans in the 650MB range. The size of the scan is a combo between

resolution, color depth (number of possible colors for each pixel), and dmax

(density range). A larger color depth provides you with better tonal range, a

larger dmax with better scans of the shadows and highlights areas.

A drum scanner might be able to provide you with 4000 dpi scans with a

dmax in the 3.8-4.0 range compared to the Epson 2400 dpi and 3.3 dmax.

So expect huge files from a drum scanner and be ready to have plenty of

RAM in your computer.

[qdb]

Doug,

 

1. Ask your lab. There are alternatives to drum scanners. Some good CCD scanners (eg, the Imacon range) offer near drum scan quality. Your lab should be able to advise.

 

2. Bigger is better, because you then won't need to have the thing scanned again if you want a larger print.

 

I use 360 dpi for most "normal" size prints. Bigger than, say, 20 x 30 and you can safely drop to around 240 dpi. You don't mention how you will print your scans, so this is for an inkjet print.

 

I scan 4x5 on my own drum scanner. A 2000 dpi scan is sufficient for sharp results up to about the size you mention. Stick to the optical resolution of the scanner. 2000 dpi is an optical (uninterpolated) resolution for my scanner. 3000dpi is not. I can scan at up to 4000 dpi, but that's a heck of a big file for a 4x5!

 

Bit depth is a seperate consideration. Most good scanners scan at least 12 bit. Because Photoshop won't work on 12 bit files, the scanner software will interpolate that up to 16 bit for output to disk. Most labs will charge extra for a 16 bit file. Advantage: you keep all the information from the scanner. Disadvantage: costs more, and you need a lot of disk / CD space to store 16 bit files. Worth the extra money if you plan on archiving your scans, or if you want to adjust them yourself in your image manipulation software.

 

It is becasue of all the variables that I purchased my own used drum scanner. I keep complete control...and its more fun!

--

Quentin

[pvp]

I'm also using the Epson 2450 -- excellent results for under $400.<P>

As for printing, you can factor in the intended viewing distance; for a 30x40 print it's unlikely that you'll be viewing it at 15", so you can probably get away with somewhat lower print resolution. OTOH, why should you? If the printer will do 300dpi, use it, your results will be that much better. FWIW, I always try for at least 300 dpi for small prints (11x14 or less) and 400 dpi will offer a marginal improvement in detail.<P>Rule of thumb: always scan at the highest optical resolution you have at your disposal -- you can always dumb it down to a lower resolution, but you'll never be able to add detail later on. Also, by scanning at high-res and doing your Photoshop work on the huge file, you minimize the size and effects of the artifacts the manipulations will produce.

[introp]

<p>You're very close with your math on #2. :)</p>

<p>uncompressed image file size = (x dimension in pixels) * (y dimension in pixels) * (bytes per pixel)</p>

<p>For a 8-bit-per-color scan, that's 3 bytes per pixel. For a 10- or 12- (or up to 16-) bit-per-color scan, that's 6 bytes per pixel. So a 40"x30" at 300dpi and 8 bit per color would be 108M * 3, or 324 million bytes.</p>

[dick roadnight cotswolds]

What resolution you need depends on the picture.

 

A picture of a group of hundreds of people will be examinied minutely at close range, so the more pixels the beter.

 

People will always look closely at large prints to see if they are over-enlarged - yours will not be at 8 : 1 but it might apear to be if you print at 300 ppi.

 

I normally scan 6,000 x 9,000 pixels to print A3 at 600ppi, but I use my own gear, so it only costs me time.

 

For a wide print I would tile a 9 x 25cm virtual transparency, scan at 4,000 ppi and print at 1,200 on 330mm roll paper: that would be OTT, but should be sharp enough to silence any wingers.

[brian_ellis3]

I only scan black and white and print 11x17 maximum which keeps my file size down, but a 324 mg file seems like a gigantic file to me. Others here are more knowledgeable than I am about digital stuff but FWIW I would think you're going to need tons and tons of RAM to work with files that size and get the print out any time this year.

[georges_pelpel]

This is a response to Brian regarding RAM.

After scanning from the Epson 2450 (2400 dpi at 4 bit) I get a 650MB file.

Once opened in Photoshop I convert it to a 8 bit/channel and end up with a

350MB file. I wouldn't say that things are super fast with such a file but it is

very useable. My computer has 512MB of RAM. Bumping the RAM from

256MB to 512MB only cost me $40. You can get a 512MB chip for about

$130.

[pvp]

In response to Brian E: yes, that's a fairly large file, but that's why we shoot LF, isn't it? :o) On the nuts/bolts level, I have 768MB of RAM and a hard drive the size of a planet, so scratch space isn't a problem. Better yet, I save the TIFs onto CDs so they don't take up any hard drive space. Storage is cheap enough these days to make a digital darkroom truly affordable, something that didn't exist a couple of years ago...

[qdb]

I have 1gb RAM and very large hard disks. I need it when a 4000dpi scan at 16 bit from a 4x5 is around 1.6 gb :-)

 

I don't want to knock the Epson 2450 flatbed scanner, which is excellent for the money, but if you are looking at 30 x 40 prints, you will want the best possible scan from your 4x5. I guarantee you will see a *big* difference in quality in a drum scan -v- a flatbed scan when printed at the sizes Doug is considering.

[noshir_patel]

For what it's worth, the Epson 2450 is good enough for 20x24 lightjet prints (I've done it). For these, most places recommend 200dpi 8 bits per channel at the final print size. For inkjet prints, 240dpi is good enough in my experience, but at large sizes, I don't see why anyone would pick inkjet over lightjet. Frankly, after seeing my photos as lightjet prints, I'm just not happy with my Epson 1200 anymore...

 

For 30x40 the math would be 30x200x40x200x3 = 144mb. Higher resolution scans sized down might be a little better than scanning at exactly the right size depending on the scanner and film (minimizing grain aliasing and such). West Coast Imaging recommends 300mb drum scans for 4x5 and I'm inclined to agree. You can also produce better crops from a higher resolution scan.

[qdb]

Noshir,

 

Agree with almost all you say (see my earlier post), but I would suggest to you and Doug that you look at the new Epson 7600 (24") and 9600 (44") wide format printers. Your 1200 is getting a little long in the tooth. The new printers (and the desktop 2100/2200) are two generations more advanced, and offer higher resolution and improved gamut and longevity.

 

However, I am biased, as I await the arrival of a new 7600 :-)

[dlabrosse]

Doug,

 

Firstly, let me state that I work as a production artist. I deal with scans all day. Mostly preparing them for print production.

 

I want to avoid some confusion here. I noticed in your initial post that you used the "lines per inch" standard. Be aware that in talking about scanning resolution there are apples and oranges. "Lines per inch" is a relic from the days when drum scanners created output straight to film for use on a printing press. "Lines per inch" is how printers refer to their half tone screens. Typically, in the old days of print production you would need double the dpi to be safe for printing at a given "line" screen value. So you would need to scan at 300 dpi to print using a 150 lines per inch half tone screen. Nowdays print production is more sofisticated and a scan at around 120 dots per cm (or 304 dots per inch) is enough for printing processes upto 175 lpi.

 

This "lpi" unit has been carried over into some scanning software and operates as 1/2 of the effective dpi of the final scan. So be aware when some people tell you that 150 lpi is enough. They are really saying that 300 dpi is enough.

 

Personally, I've found any image produced at 150 dpi on any type of device (lightjet, inkjet, Pictro or colour copier) not to meet my expectations of "photographic quality" - 300 dpi is closer. The Beauty of LF is in the tone that one can get from a big original. Why waste all that information? So when scanning LF originals I tend to get the biggest scan practicable.

 

It is hard to beat the quality of a good drum scan. Given the choice, I will almost always opt for a drum scan if it can be afforded. But everyone has their own preferences. Some people find flatbed scans are more than adequate for their tastes. Take one tranny/neg and work with your Lab on different scanning and output options (providing your lab has a drum scanner) to see what pleases your eye.

[kelly_flanigan1]

What an interesting thread..........<BR><BR>Many times court exhibits that I print are 30x40 inches...The attorney gives me a COLOR COPY of a poor underexposed POLAROID that a patrolman shot on the scene of the crime or auto accident........Since this is my input; and the accident is many times 3 years ago; I must do my best to make a truthfull best of my abilities 30x40 color inkjet print.....getting a 35mm negative from a point and shoot camera is a dream easy job compared to working from a 2.1x2.1 color copy of a lame polaroid...........<BR><BR>The key to how well posters look is the viewing distance.........Many billboards can be printed at 6 dots/inch ; because they are viewed far away......I printed the same photo 2x2 foot at various dpi's....The coarsest is at ONE dpi; the finest is at 300 dpi........A many distances one cannot tell the difference between a 50 dpi and a 300 dpi image