How To Convert Your Digital Compact’s Zoom Lens To A 35mm Prime

This month I’m committing to a single camera again, part of my One Month, One Camera project. For December it’s my Panasonic Lumix LX3.

I thought I might try some different focal lengths, having used it almost entirely at 35mm previously.

So I went with its longest zoom of 60mm for a while, but found first that the reduced minimum focus was too limiting (only 0.3m at 60mm, rather than 0.05m at 35mm), plus I just wasn’t getting enough in the frame.

This is a strange phenomenon I’ve not quite yet figured out, as with DSLRs I often shoot with 50 and 70mm lenses, which with their APS-C sensors and 1.5x crop factor equates to a field of view of 75mm and 105mm respectively, obviously longer than the 60mm of the Lumix.

When I pick up a compact camera though, 35mm just feels like the view I should be seeing, the one that makes most sense. 

There is an almost infinite range of digital compact zooms that can be used at 35mm.

The problem is usually this isn’t their widest, default setting, so every time you power up the camera, you have to zoom into 35mm again.

This is further compounded by the fact that most cameras don’t tell you which 35mm equivalent focal length they are zoomed to.

The most common display is 1.0x, 1.5x, 2.0x etc.

It is possible to translate this once, then remember what you need.

For example, my Sony Xperia phone’s lens starts at 25mm. So I nearly always zoom to 1.4x, which is 35mm (1.4 x 25 = 35). I’ve done it so many times now, I don’t really think about it, it’s a automatic habit.

This works, but still needs that extra step, every time. Even if I then view the shot I’ve just taken, going back to shoot again the lens reverts back to 25mm, so I have to zoom again.

Which is pretty rubbish, for those of us who use their phone mostly for people shots and don’t want them to appear to have faces as long as horses.

Some cameras improve on this by displaying the actual focal length, not the multiplier.

But not many.

And then usually the actual focal length of the lens (say 4.6mm or 5.8mm) doesn’t mean much to us, when we’re used to a familiar 35mm equivalent.

Who can easily translate in the field from memory what 4.6mm on their camera with its 1/1.23″ sensor equates to in 35mm terms?

Some don’t give you any indication of focal length at all, you’re just guessing.

So how do we overcome this?

How can we convert a zoom compact to one we can just pick up and use as a 35mm prime immediately, every time we use it?

There are two options I’ve come across.

1. Use a camera with Step Zoom.

There are a number of Ricohs that do this – I’ve used the GX100 and CX1. I believe a number of other cameras in the CX and R ranges also offer this – check the instruction manual online to check first.

I picked up a CX1 for about £20. Later models generally go for a bit more. My GX100 was around £50, and worth every penny.

What this means with the GX100 for example, is you can enable Step Zoom, and each time you push the zoom rocker switch it goes to the next step in the sequence, then stops.

The steps with this model are 24, 28, 35, 50 and 72mm.

Aside from the slightly strange 72mm maximum, these faithfully replicate focal lengths that most film photographers are/were very familiar with.

Even better with the Ricoh, you can set up the two custom memory slots on the main mode dial (MY1 and MY2) to remember which zoom step it’s at too.

In practice with my GX100, because I always use it for b/w photography at ISO400, I have MY1 set as 28mm, and MY2 at 35mm, and everything else the same.

It’s like having a digital compact with two prime lenses – one 28mm and one 25mm – but being able to switch between the two just by flicking between MY1 and MY2 on the mode dial.

Most of the time I’m at 35mm, but if I do want 28mm for some wider shooting now and then, I just switch to MY1 on the dial and I’m immediately there.

It’s one reason why I love Ricohs, and the GX100 is quite possibly the best digital compact zoom I have ever used.

It feels like it was designed by real photographers, so it’s intelligent and intuitive for other photographers to use.

Anyway, on to the second main option.

2. Use a camera with Zoom Resume. 

This is a feature I’ve only seen on Lumix cameras. Both my higher end (in its day) LX3 and the much more consumer orientated TZ2 have it. They cost me around £75 and £15 respectively.

All Zoom Resume means it whatever focal length the lens is at when you switch the camera off, it remembers, so when you power up again, it reverts straight back to that focal length.

Simple, and super effective.

Initially there is a hurdle to overcome, and that is knowing which focal length the lens is at, in the case of my needs, 35mm.

With both cameras (and most other digital compacts) it’s possible to find this out though.

What I did with the TZ2 (as outlined in more detail this post) was take a shot at the widest zoom, then flick the zoom to go in just one “notch”, take another picture, and so on, until I was at maximum zoom.

From the EXIF data from the resultant set of images I had, I could then see what the 35mm equivalent focal length was, and the corresponding maximum aperture.

Both the TZ2 and LX3 show you the 35mm equivalent focal length anyway in the EXIF data, as well as the actual.

I didn’t realise this at the time with the TZ2, so analysed it manually.

I noted the widest and longest focal lengths, and their 35mm equivalents (both can be found in a review of the camera or certainly the manual), then work out the crop factor and what this equates to for the other focal lengths.

With the TZ2 I then had this table –

Most of the maximum apertures were unique to a focal length, eg only 28mm uses the maximum aperture of f/3.3, and only 35mm uses the maximum aperture of f/3.7.

So I then knew that if I was in a low light place, and zoomed in gradually until the aperture display read f/3.7, I’d be at 35mm.

With the Zoom Resume feature enabled, I then didn’t need to touch the zoom again.

Every time I switched it on again, the camera would remember where it was before, and revert to 35mm.

So like the Ricohs above, you have a digital compact that’s always at 35mm when you power up.

With the Lumix LX3, I use the same Zoom Resume feature, but a little less calculation was required initially.

I found a table online like the one above that told me the maximum aperture at 35mm was f/2.3, and again this maximum aperture was unique to 35mm.

As I use the LX on Aperture Priority, I just zoomed right out, set the aperture to its maximum (f/2 at 24mm), then zoomed in step by step until the aperture said f/2.3, and I then knew the lens was at 35mm.

With the Zoom Resume enabled, like the TZ2, then I just switched off, knowing that every time the LX3 powers up, it’ll zoom straight to 35mm again.

Even if I didn’t have Zoom Resume on the LX3, just by doing that initial research and discovering that the maximum aperture of f/2.3 is unique to 35mm, I could just use that info each time, zoom in until the aperture displays f/2.3.

But the Zoom Resume makes it much easier.

In theory you can apply a similar approach to most digital compacts, and in effect convert them to a prime lens camera.

Having some way of either setting specific zoom steps and displaying them – like the Ricohs – or a Zoom Resume – as the Lumix cameras do – enables you to do it just once, then forget about it and enjoy using the camera at 35mm (or whatever other focal length you choose, the same theory applies).

But even if the camera doesn’t have this memory function via Zoom Resume or a custom/MY setting on the mode dial, it can still be done. 

It’s easier with a camera that can shoot aperture priority.

Once you shoot a picture at every zoom position and figure out the max aperture for your chosen focal length (eg 35mm for me), then you can just zoom in each time you power up the camera to this maximum aperture, like I explained above with the LX3.

By using a camera’s power saving settings (which most seem to have) you can set it to go to sleep after say five minutes to spare your battery, but not power down completely.

With most cameras this shuts off the screen etc, but remembers the mode and settings, and doesn’t move the lens, as when you power down fully.

So on any one photo walk, you only need to switch the camera on once at the beginning, set the focal length, then forget about it and treat it as a prime lens the rest of the walk.

Personally I’m not a great fan of zoom cameras, and don’t use them like most people.

Indeed if my Ricoh GRD III had a 35mm prime lens rather than a 28mm one, it’s unlikely I would have bought the GX100 or the Lumix LX3 at all.

But despite the GRD being excellent in virtually all other areas, 28mm is often too wide often for my style of shooting, and gives too much distortion.

So I learned how to use other zoom cameras as 35mm prime lens cameras, using the methods outlined above.

I hope this is some use for you, if you’re someone who finds the widest focal length of a zoom too wide and, like me, hasn’t found a digital compact with a prime lens at your favourite focal length.

How about you? Have you used this kind of approach before yourself? How do you usually use a camera with a zoom lens? 

Please let us know in the comments below (and don’t forget to tick the “Notify me of new comments via email” box to follow the conversation).

Thanks for looking.

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