About to test Canon 5D against my Mamiya 645AF with film...

Hi

 

I'm soon to rent a Canon 5D for a day to test how it performs against my usual set up - a

Mamiya 645AF with 55mm, 80mm and 150mm lenses, Portra 400VC film (sometimes

hand-printed, sometimes scanned on an Imacon and retouched).

 

(I shoot portraits on location, with a mix of flash and ambient.)

 

I have a few questions:

 

- Which lenses do I need for the Canon to match my three 645 lenses? I always shoot

vertical, and I will be cropping the 5D shots down to match the proportions of the 645

frame, so I need to match coverage across the short side of the frame (24mm) not the long

side (36mm).

 

- I very often have straight lines in my pictures, often running parallel to the edges of the

frame, and I've always been wary of the distortions (barrel, pincushion) created by zoom

lenses - maybe these issues have been resolved? Are primes still regarded as optically

superior (sharper)?

 

- I don't like the 35mm aspect ratio at all (for portraits). Is there an easy way to mask off

the viewfinder in the Canon for a 645 ratio?

 

- Anyone make similar tests? Conclusions?

 

Thanks

 

Elliot

Sorry, one more question:

 

- It's been a while since I shot 35mm... How much do I have to open up the aperture to

match the depth-of-field on my 645AF? One stop, two stops?

Since you will crop the 5D the conversion factor would be 24 / 45 = .533x

 

55 x .533 = 29mm. You can figure out the rest.

 

There are a few ways to look at files and compare on a computer. I have the best luck scanning film at around 2000-2500 dpi. Sometimes I will go higher. At any rate, scan a shot and resize it to a 5d file size or resize the 5D shot to the scanned file size. Also you could overscan the film, then resize both to a print size like 24x32 at 300 dpi.

 

Primes are typically sharper, but especially better at the edges with a high mp full frame sensor.

 

Probably the biggest issue for me was getting used to the DOF.

Use the following calculator from Julian Loke to handle your focal length and DOF questions:

 

http://ca.geocities.com/lokejul/jlcalc.htm

 

Lens distortions vary lens by lens - even primes aren't perfect, particularly at wide angles. However, you can use software such as PTLens to correct distortions at a small cost in image quality due to the interpolations involved.

 

http://www.vanwalree.com/optics/distortion.html

 

There isn't a good way to mask the viewfinder - doing so would upset exposure metering in any case.

 

There have been plenty of FF tests against MF film with 1Ds series bodies. Conclusions vary according to the predisposition of the tester and the techique used in making the comparison including scanning and subsequent image processing. To get a range of points of view, look at tests by Michael Reichmann (digital evangelist), Ken Rockwell (still supports film), and William Castleman for a start.

 

It's best to make your own comparisons with your choice of equipment and technique - they will at least be valid for you.

Ohh and try some E100G. Its very clean and sharp. On my setup it is almost a dead ringer for digital at around 2500 dpi.

 

You can figure out the DOF difference here.

 

http://www.dofmaster.com/dofjs.html

-645 is 42mm wide, i.e. you need a factor of 1.75: 55mm->31mm, 80mm->45mm, 150->85mm. I'd recommend a 24-70/2.8L for the two wide ones, and a 85/1.8 for the last one.

 

-Good zooms are well corrected for distortion (e.g. 24-70L does well), and some primes aren't perfect (e.g. 50/1.4 at close distances). The 24-70L compares very well against wide primes in the sharpness department.

 

-Since the focusing screen can be changed, you can take it out and mark is appropriately. Darkening it too much might confuse the meter (though if I remember correctly the meter doesn't really look at the edges, so if you mask 2mm on either side you might still be fine). If you actually mark thin lines at 2 and 4mm on both sides you'll have more opportunities for positioning the focus points witin your target frame.

 

-As far as DoF is concerned, you need to open by 1 2/3 stop (i.e. divide the value of the f-stop by 1.75).

Also: while they're not exact matches for the lenses you use, you may want to try a 35/1.4 and 50/1.4.

Many thanks for the info...

 

So it's either: 24-70mm and 85mm

 

Or: 28mm, 35mm, 50mm and 85mm

 

I rarely shoot at wide apertures, so the wide aperture primes would only be of interest for

the brighter viewfinder.

 

I really need to find a solution for masking the viewfinder. (Actually I need to find a

solution for my Mamiya 645AF - I'm often asked to shoot square, and I mask the screen

with bits of tape, but the screen is now a gummed-up, scratched-up mess). A friend was

recently shooting with an H1/Phase One, and that had a nice acetate frame that you drop

on top of the screen to mask it off. So something like that would be good... but I don't

want to throw off the focus. Oh wait, I just want to mask top and bottom of the vertical

frame, not the edges, so a frame won't work... Hmmm... I use a handheld meter so not

worried about throwing the camera's metering system...

 

Thanks for the tips. Very helpful.

 

Elliot

Cropping the 35mm frame to a square will effectively drop the resolution to around 5 megapixel and your 645 will win the race hands down with plenty room to spare. This is from someone who sold his Mamiya 645 kit for a 10D and has had the 1Ds and 5D...

Ben: I don't know what you've been smoking, but I want some ;)

 

Cropping to 4:3 will give 11.3 MP, cropping to square will give 8.5 MP.

Interesting comments, Ben - though the 5D cropped to a square would be 8.5 megapixels.

 

If the results from the 5D cropped to a square are clearly inferior to 645 film cropped to a

square, then I might not bother with the test, as I find that 645 film is barely good enough

when cropped to this format. (This is for single page reproduction (full bleed) in a 10

inch square magazine).

I would expect 10 inches to be "just fine". That's almost 300 dpi, which

I consider to be more than enough (I'm very happy with 240dpi). Our standards of quality may vary, of course.

 

Cropping to a square allows to avoid 4.6mm of image circle, such that lenses that are usually good "everywhere except in the far corners" will be good everywhere after cropping to a square.

Thanks Jean.

 

There's quite a price difference between the zoom and prime options:

 

24-70 f2.8 zoom + 85 f1.8 = 1275 British pounds

 

28 f2.8 + 35 f2 + 50 f1.8 + 85 f1.8 = 715 British pounds

 

(Maybe swap the 28 f2.8 for the 28 f1.8 and the total = 900 British pounds)

How about a digital back for your Mamiya? You don't have to invest in a new system.

I've been waiting a year for the Mamiya ZD back, but I now doubt whether it will ever be

released.

 

I can't afford a back like the P25. I guess there might be cheaper options - I haven't really

looked into it...

IMO, unless there is an immediate void that only a 5D can fill I would wait for the ZD Back or prices to go down. Shoot film for now. If possible rent a 5D or 1Ds mark II and try out the system. I shoot both film and digital, depending on the situation.