It's easy enough to make one for yourself, you'd need a 5x7 back assembly (from any manufacturer) and attach that to a piece of wood or metal that fits onto your Tachi.
Printable View
I search for a 5x7 reducing back for my Chamonix in the past but after packing all items : 8x10 camera, lenses and holders I decide that I will not add a 5x7 reducing back (fragile too) and 5x7 holders to this already big and heavy pack.
My suggestion is to look for a nice wooden 5x7 camera (a lot of models available) with a 4x5 reducing back. The 5x7 is more like a big 4x5 so it make more sense to pack one camera and 5x7 and 4x5 holders with about the same lens kit for the 2 formats.
Once you will have found this camera, you can sell your 4x5 Toyo!
I have to agree with Ginette here, I also love my 8x10 Chamonix but my 4x5 reducing back is just another thing to bring along and I think I should sell it and get more 8x10 holders with the money :)
I also agree with the above poster who mentioned 5x7 as being a better landscape format.
I think as long as you don't care about color film shooting (or are ok with the special orders by Keith Canham for Kodak C-41 film), then 5x7 is probably the best compromise.
Good luck!
I walk a long ways when I shoot usually for miles. I break in the afternoon to unload/load the holders back at home base (motel) and then go out again. I like the idea of ditching 4x5 for 5x7 and while it sounds great and all but how many 5x7 holders I can carry will be the key. The camera and lenses may be slightly bigger/heavier but 10 5x7 holders is a big deal compared to 10 4x5 holders. I know I can shoot less by shooting better but maybe someday! Are folks here that confident in your metering skills so not to bracket? I usually shoot 2 sheets per scene but with 5x7 I just won't have enough.
I never bracket, not LF or even medium format, not even with transparency film. If you are careful and accurate, you shouldn't need to bracket. I now shoot 8x10 and only Cary 3 or 6 holders with me at any given time. I don't re-load usually, just shoot till I'm out, but that forces me to really choose when an image is worth it. I also shoot TMY-2, Acros100, and Velvia50, all in 8x10. So screwing up or bracketing would be ridiculously costly.
Fortunately (or unfortunately) most of those films aren't available in 5x7, so you're probably shooting Ilford? Which is at least less costly, and so bracketing isn't so bad.
But ultimately as o originally asked, are you currently unhappy with your negatives right now? Are they printing too grainy that you feel you need a bigger size?
And don't forget if one is highly weight and bulk conscious then his/her lenses are probably highly optimized for their format of choice. So a set of five lenses for 5x7 may be a bit heavier and larger too. For a two or three lens kit this may be negligible enough. Then the tripod and head might need to be a bit bigger/heavier and as mentioned before the holders are larger. If one only carries a couple of holders and a changing bag the latter may not be a concern.
Absolutely, and I decided to accomplish the hat trick of 4x5, 5x7 and 6x17 with the Canham MQC 5x7, with 4x5 reduction back (which is a bit different from other reducing backs), and the 6x17 roll film back. The MQC is not that much bigger or heavier than many 4x5 field cameras (except of course the ultralights). Here's how it looks:
Attachment 133923 w/5x7 back
Attachment 133924 w/4x5 back
Attachment 133925 the 5x7 to 4x5 reducing back for the MQC (just try to find photos of this anywhere else)
Attachment 133926 and of course with the most excellent Canham 6x17 motorized roll film back
A 5x7 camera can easily be a 4x5 camera. There are many cameras which can be for 4x5 and 5x7 with the change of a back. Many lenses which are used for 4x5 can also be used with 5x7, some of them with quite a bit of movement.
Color with 5x7 is an expensive route. 5x7 color film is special order and quite expensive. 8x10 can be cut down to 2 sheets for 5x7 for each 8x10 but it is fiddley and 8x10 is pretty expensive, too. Yes, a 6x17 roll back can be used with a 5x7. Shooting color only in 4x5 or roll film would get around these problems but, again, you wouldn't be shooting 5x7.
B&W with 5x7 is available in as many emulsions as 8x10 and almost as many as 4x5. B&W can easily be processed at home. 5x7 enlargers are kind of rare these days but, if you look, you might find one at a bargain because there are but few in the market for any kind of enlargers these days. 5x7 contact prints are very nice. 4x5 contacts are just a little bit too small to be viewed easily but 5x7s mounted on 8x10 boards can be viewed with advantage at about arm's length. Equipment for contact printing is pretty minimal. You can use the enlarger and trays you have already. For someone with no enlarging gear, you need a controllable light source, a piece of glass and three trays. The light source could be a cheap 35mm enlarger, a switch and a metronome.
It seems to me that the most cost effective way to do large format photography these days is the 'hybrid approach'. Expose on film, scan and print digitally. Using an Epson 750 at home will do an excellent job on all except on your very, very best ones which you want to print really big and, for those ones, you send 'em to Lenny or another professional scanner. Materials for traditional printing are getting pretty expensive these days and there are lots of quality printers who will get your stuff back quickly with good quality. As long as there is film, the 'hybrid approach' is going to be around unless the masses go 95% keeping their photos on smartphones and iPads.
So, if your camera will take a 5x7 back, you just need that back and as many holders that you think you need. Film is about twice the price as 4x5. Your lenses will probably be OK. If you want to make enlargements at home, you will need a 5x7 enlarger. If contacts are fine, whatever enlarger you have will work. Color is expensive in 5x7 so, when you want it, use your 4x5 back. Otherwise, B&W is fairly easy to obtain in 5x7.
If you need to change cameras to try 5x7, it might be fine to get something inexpensive like a B&J or a 2D to see how you like it. If you like it, the B&J/Kodak might be fine or you could sell it probably for what you paid and get a better camera which will do 4x5 and 5x7. Or, if you find you don't like it, you can sell it for about what you paid for it.